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Ren^: Descartes was born on the 31st of March 1596 
at La Haye in Touraine not far from Poitiers. His 
father was a gentleman of good family who had retired 
from military service and had become councillor of the 
Parlement of Brittany. Rene was the third son. He \ 

was sent at the age of eight to the^^^ewly established . J^ 
Jesuit college of La Fldche in MaineV He stayed there ^ ' 
for eight years, going through the full course. of stud^r;"" I ^ 
and showing in the last two years extraordinary prproci fyKP^'^-^^^^ 
in._ mathematics. Descartes all his life retained "the f/\ 
warmesFalfection f oriiisf old college and laid great -store 
on the approbationu-ol-4iis-~j6Suit teachers. Here, too, he 
made the acquaintance of his great friend, Mersenne. 
Mersenne later became a monk and eventually head of 
a convent in Paris. He was a man with a great gift 
of friendship, and his cell in Paris became the centre 
of philosophical and scientific discussion. Descartes* 
correspondence with him was constant and continuous, 
and ended only with Mersenne's death in 1648. Descartes 
not only found in him a loyal friend, but was through 
him enabled to get in touch with all the most important 
thought pf the time. jj- X ^> 

In the first part of the Discourse on Method Descartes 
has related how after his studies were finished he came 
to the conclusion that for him further book-learning was 
unprofitable, and resolved " no longer to seek any otlxiyr 
science than the. knowledge of myself or of the ..great ;\ 

book of the world." Seeing the world meant enlisting 
in a foreign army, and the years till 1619 were spent by 
Descartes in the Low Countries, serving under Prince 
Maurice of Nassau. It seems to have been a curious 
existence: camp life with a certain amount of ''fighting, 
a good deal of leisure to study and write, and "discussion 
with the eminent mathematicians of the day who were 



Discourse on Method 

serving as engineers. In 1619 Descartes, tired of a 
service in which as a Roman Catholic he had little 
sympathy, left the Low Countries and joined the army 
of MaximiUan, Duke of Bavaria, on the Danube. There, 
4te- tolla u &4a-iW^-of-^5 tfagmerrtsr-he passed the most 
momentous day of his life, "being full of enthus^sm 
and having discovered the basis of true science.'^ -Hr 
^Yas^j rob a bly thg same - day go io do c crib ed-ia-4be-beg«i-- 

even ts^.adjnirab ly IftiiBtrate that combination of simple 
C^THoTic piety aric J ' Su e nlific zeal vvl i i&h i s chara.cteristic 
' of DesGAftesLLUfe and writings. It was an experience of 
troubling dreams, of earnest prayers for light, ending 
in a vow to make a pilgrimage to our Lady of Loretto. 
Its outcome was a resolve, w^hich the Method describes, 
j;rto " sweep wholly away " all that he had learned, the 
1 formulation of the Cartesian method of doubt, and the 
\ discovery, by the application of algebra to geometry, of 
\ the generality of mathematics. From this time forward 
Descartes)ievoted himself to working out his discovery. 
He quitted the army in 1621 and spent the next few 
years inr^-^ider travel, till finally in 1628 he settled in 
Holland as the country where he would be left most 
undisturbed to study and write. His investigations 
were by this time not confined to mathematics, but 
included chemistry and anatomy. The first statement^" 
of his philosophy, Rules for the Direction of the MindK 
though not published till after his death, was written at^ 
the beginning of his stay in Holland. It is an admirable*^ 
statement of Descartes' mathematical method. He 
was also busy about thh (tum^^riting a treatise, to 
be entitled " Le Monde, 'V^3fcTt^5%-3eecribod in PgnrV" 
j^ t b Q Dt s c o urse nrt Meth o d . Beginning with astronomy 
and showing how the world might have come into being 
according to physical laws', it passed oj^ to a description 
of " animals and particularly of man,'|p,nd proposed to 
give a mechanical explanation of the human body. The 
body is looked upon '' as a machine made by the hands 
of God, which is incomparably bet tei^ arranged and 
adequate to movements more admirable than is any 
machme of human invention. '-%» The treatise had 


Introduction ix 

evidently much in common with Galileo's work and 
Harvey's treatise on The Circulation of the Blood, 
with both of which he became acquainted about this 
time. It was just going to be published when in 1633 
the news came that Galileo had been condemned by the 
Holy Office, that his book had been burnt and he had 
been compelled to abjure. Descartes was much disturbed 
by the news. He had, as he says, perceived^^othing 
hereticalin Galileo's doctrines. His own treatise affirmed 
some otfthem. He withdrew it and gave up in the 
meantime all thought of publishing. Descartes was not 
of the stuff of which martyrs are made. Moreover, he 
had a deep and sincere devotion to the churchand 
respect f or "ite autTiofity 7 " Its "condemnation was, at the 
time at least, enough to shak e his co nviction of the 
truth of his_conclusions. Further, being martyred was 
not his business. He felt that what he wanted was to be 
left alon e to disco ver the truth, and for that he must 
have tuneand quietT box his work's "sak^elt was not 
wortlftiis while To ge^ into trouble with the church. He 
turned to other studies, and in 1637 published the 
Discourse on Method\ i ^ ^Yki(jh. comoG first in thi '5 volum f'. 
Its full title was, A Discourse on the Method of rightly 
conducting the Reason and^eeking Truth in the Sciences, 
Further the Dioptric, Metebr^s and Geometry, Essays in 
this Method. The Dioptric hXd been made possible by 
the recent inventioiTol the tele^<;jope, and was a study of 
the natureof li ght, of ifefraction^ st-gd of optical delusion. 
The treatise upon Meteors was reall^,a general exposition 
of Descartes' Ijh eory jpi matter whicnNvjbie identified with 
extension, andfan attempt to apply it t^the explanation 
of many natural phenomena. There i^\too little em- 
pirical knowledge of phenomena behind'^Hhe treatise, 
but the theory itself has been of great influence|l The 
Geometry^ the most famous and epoch-making part of 

his SCienti£c m^k)\ was an f^vpogjltinn of hif^ npw analytir 

geometiy^^he ^y^blication of the Discourse made 
Descartes famous, but it also, in spite of his previous 
behaviour, made him an object of suspicion to the more 
extreme ecclesiastics, Calvinist and Roman Catholic alike. 
It was partly to aUay such suspicions that he published 

X Discourse on Method 7^ 

in 1641 his Meditations on the First PhilosophyS/J^^y 
were dedicated to the Deaif^nd Doctors of.tfe^ Sacred 
Faculty of Theology in Paris, and their^tirport was to 
show that the new method of philosophy, in spite of its 
fundamental difference from scholasticism, could produce 
irrefragable arguments fortlie most orthodox conclusions. 
Before publication M-ersenne had shown the manuscript 
of the Meditatiorcf to some of the leading thinkers of the 
day, amoijg-lhem Arnauld, Gassendi, and Hobbes, and 
from tk^mcollected a series of Objections to which in the 
seoelid edition of the Meditations Descartes wrote repUes. 
^iSescartes' later writings were dedicated tcCjtwo noble 
ladies. In about 1642 he had been introduced to the 
Princess Elizabeth of Palatine, who was then resident 
at the Hague. With her he conducted a long corre- 
spondence on philosophical quest^ns^ andhe^^^ed^ted 
to her his Principles of Philosophy^ a^^ybm^eSdmm^ 
views on philosophical and scientific subjects. The 
selections translated in this volume are confined to the 
more philosophic part of this work^ These include a 
restatement . of his metaphysic^^views, a further 
elaboration of his doctrine of mcrfion — the most dif&cult 
and ambiguous pajt of hk^^liilosophy — and an account 
of the relation of^body^-^nd soul and of the senses and 
the understanding. /O'he more strictly scientific part 
contained an astronom^Nsomewhat on the lines of Galileo, 
but avoiding his unorthotiQxy, and an account of the 
physical structure of the earai^^In 1646 he was intro- 
duced to Queen Christine of Sweden, who was keenly 
interested in the new philosophy and science. He 
corresponded with her and wrote for her a spefcia^ _ 
psychological treatise on The Passions of the Soul, liis ij 
last published work. In 1649, at her earnest request, he • 
went to the Swedish Court at Stockholm. This change 
of residence, and even more the painful necessity of 
getting up at five o'clock in the morning to instruct his 
royal pupil, proved fatal to him. Descartes iJiad all his 
life been accustomed to lie in bed and study till late in 
the morning. He caught inflammation of the lungs, 
and died in February 1650. ^^^^ 

1 have given in some detail the chief events of 

Introduction xi 

Descartes' life, for it is hard tojinj^stajidthe com bina- 
tion in his thoug ht of elements apparently diverse unless 
we realise'" the circumstances "oT'lESF TSne" at " wEicH ' he 
lived and hjs sittitude towards them. T)escartes Uved 
in the time that saw the beginnings of modern science, 
and himself contributed as much as any one to that 
beginning. Though without the experimental genius 
of Galileo or Torricelli, he far more than Lord Bacon had 
an insight into the theoretical basis on which the new 
discoveries res_ted. His great contribution^ to s cience ,/,/>, 
itself was mathem atical ) He was always m ore conc erned 
with general principles of method~ttSnwi|h2SI32S5ed 
work_of observati on" Hrs~'Tcience was essentially ^ 
rationalistic^. Just lor that reason his scientific work ^ 
was full of the most daring prophecies, which became 
the assumptions of nineteenth-century science. He had 
had a vision of ^Jlgw method of T^n owlec j^e. Refusing ^"t 
to let himself be hindered by lack of adequate informa- 
tion, he thought out what the constitution of the world '( 
and man must be if they were to be clearly understood. 
He lived at a time before t he speciali sation which is so 
characteristic of modern science had made its appear- 
ance. It was possible then for one man to master all 
that was known in all the sciences, physics, chemistry, 
astronomy, and anatomy. He looKed beHiiiSJjthe 
differences of ffiese'separate inquiries toTHeir common 
method and assumptions, and formulated for them a 
common ideal. He was the author and the prophet of 
the conception of mechanism, under the guidance of 
which modern science has made its greatest achievements. 
Long before anything could be done to work out such 
a conception in detail, he maintained that t he universe 
as a whole^ and in its det;^.ils v{^,^ f.n be understood as a. 
mechanical system, and asserted this of the nature of S 
the~human body, and the whole nature of animals, as 
well as of the structure of the solar system. Of late 
years scientific thought is becoming conscious of the 
limitations of this ideal. It involves, as we shall see, 
certain theoretic impossibilities. But the services it 
has rendered to modern science can hardly be over- 




Discourse on Method 

The boldness of Descartes' thought had, as we have 
seen, its Umitations. He Hved at a time when political 
freedom was unknown, and when that complete liberty 
of thought which modern science claims as its birthright 
was hardly dreamt of. He was himself a sincere and 
devout son of a church which claimed not only absolute 
authority within its own sphere, but the right to assert 
what was or was not included in that sphere. In the 
last paragraph of the Principles Descartes says, *' I 
submit all my opinions to the authority of the church. 
Lest I should presume too far, I afi&rm nothing, but 
submit all these my opinions to the authority of the 
church and the judgment of the more sage; and I desire 
no one to believe anything I may have said, unless he 
is constrained to admit it by the force and evidence of 
reason." The conflict is evident. Descartes believed 
that the force and evidence of reason was appreciable 
by every man. His test of truth, that which we clearly 
and distinctly conceive is true, was one which every 
individual could and must apply for himself. But over 
the authority of the church no individual had any control, 
and the fact that an argument had been approved by 
the reason of the individual man was no warrant that 
it would be approved by the church. Against this 
authority he had no thought of protesting, and his 
sincere acceptance of it is of the utmost importance to 
his philosophy. Had he cared only for science and its 
assumptions he might have had recourse to equivocation 
and evasion to escape ecclesiastical censure. He might, 
like the genuinely sceptical writers of the next century, 
like all freethinkers who live under an authority which 
they despise but dare not affront, have become a master 
in the art of knowing what to say and what to leave 
unsaid. In that case, though his language would have 
been influenced by authority, his thought would have 
been free of it. But with Descartes the conflict between 
reason and authority had to be fought out within him- 
self. He had somehow to find room for both in his 
philosophy if his own convictions were to be satisfied. 
At the same time no real reconciliation of the two spheres 
of science and religion was possible for him. For the. 

Introduction xiii 

truths of religion had found expression in the terms of a 
philosophy against which all his thinking was in revolt, 
and he had to take them as they were or not at all. As 
his more cynically-minded contemporary Thomas Hobbes 
remarked: '* It is with the myster ies o f our Religion as 
with wholsome pills for the sick, which swallowed whole, 
have the virtue to cure; but chewed are for the most 
part cast up again without effect." _ 

Descartes had never any thought of " chewing *' or in 
any way analysing what his spiritual doctors prescribed. 
He was concerned to prove that such spiritual pre- 
scriptions were necessary, and to justify that view of the 
world upon which they were based. This is the source 
of Descartes' dualism. He had^ to find room in his 
system for two entirely ^sp arate wo rlds. He never 
really gave any explanation of their conne ction except 
to say that they were both thereaii3 thaFtheir inter- 
communication was miraculous. The sharp separation 
which he maintained between them was equally harmful 
to both. It produced on the one hand his conception of 
a purely mechanical world which is the basis of modern 
materialism, on the other the beginnings of that form of 
idealism which shuts the soul up in itself and tends to 
throw doubt upon and even to deny the existence of the 
external world of objects. For the soul conceived of as 
separate from' the body therexan be no object but itself, 
or a God separate from the world. The soul's knowledge 
of the world becomes a mystery which it is hard to go on 

With these considerations in mind we may proceed 
to examine Descartes* method and the outlines of his 
metaphysical conclusions. Descartes, as we have seen, 
thought of himself chiefly as the discoverer of a new 
method, and his first two works, the Rules and the 
Discourse, are chiefly an exposition of it. The beginning 
of the new method is implied in his review of his studies 
after leaving college. History, eloquence, and poetry 
are described as pleasing but hardly serious pursuits. 
Theology is notjo be ** sub mitted jtgJlifiJnipQteacy of 
our reason P^^philosophy andjogic " aff ord the means_o f 
discoursing with an^p"peafan£^j^ in all matt ers/ ' 


xiv Discourse on Method 

The syllogism Descartes dismissed as a means of express- 
v.^ ing what was known already, not as an instrument of 
discovery. Mathematics alone is highly approved^' on 
account of the certitude and evidence of their reasoning." 
The only fault Descartes had to find with them was that 
the relations of the different branches of mathematics 
had not been thought out. This defect he was himself 
to remedy, and with the perception of the common 
mathematical method came the notion of this method 
being common to all the sciences. 

Descartes' exposition of method has two sides. It is, 
in the first place, an account of the method which he had 
actually pursued in his mathematical discoveries. As 
such it is of great and permanent value, as a clear state- 
ment of the method of the mathematical sciences. But 
the scope of the exposition becomes enlarged when 
Descartes proceeds to apply this method to other spheres 
of inquiry than the mathematical, notably to metaphysics 
and also to enunciate the philosophical principles upon 
which it depends. These include the famous Cartesian 
method of doubt, the discovery of the ultimate principle, 
/ thinky therefore I am, and the proofs of the existence of 
God. They involve, as we shall see, certain very serious 
difficulties. The simple exposition of method is pre- 
sented in its best form in the Rules for the Direction of 
the Mind, but it is also given in the four rules at the 
end of the second part of the Discourse. Its novelty 
consisted in the rejection of the syllogism and the 
af&rmation of the truth that the discoveries of reason 
are not made by deducing the particular froinlthe 
universal, but from perceiving the universal" in the 
individual instance. It asserts a clear distinction 
between reason and either perception "or imagination. 
Neither of the latter faculties give knowledge, although" 
they may help or hinder it. Knowledge is given only by 
the clear vision of the intellect. This Descartes calls 
"^intuition, and describes as follows: (''By intuition I 
understand, not the fluctuating testimony of the senses, 
nor the misleading judgment that proceeds from the 
blundering constructions of imagination, but the con- 
ception which an unclouded and attentive mind gives 

Introduction xv 

us so readily and distinctly that we are wholly freed 
from doubt about that which we understand. Or what 
comes to the same thing, intuition is the undoubting \ 
conception of an unclouded and attentive mind, and 
springs^qm the light of reason ajone; it is more certain j 
than^eduction itself, in that it is simpler, though / 
deduction cannot by us be erroneously conducted. / 
Thus each individual can mentally have intuition of the 
fact that he exists, and that he thinks ; that the triangle 
is bounded by three lines only, the sphere by a single 
superficies, and so on. Facts of such a kind are far more 
numerous than many people think, disdaining as they 
do to direct their attention upon such simple matters." ; 
Descartes* intuitio n carries its cer taintyLmtlLit'. The 
truths which it grasps are self-eviden t, and c ould a cquire 
no fur ther certainty by being ded uced from_or connected 
with anything-elsj^. Method is needed so to arrange the 
objects of our inquiry that we may be able thus to 
intuite them. It might seem at first sight as though 
we should thus reach only a large number of isolated 
propositions, but as Descartes says, insight into the 
connection of different self-evident propositions is itself 
the work of intuition. / " Method consists entirely in the 
order and disposition oTthe objects towards which our 
mental vision must be directed if we would find out any 
truth. We shall comply with it exactly if we reduce 
involved and obscure propositions step by step to those 
that are simpler, and then starting with the intuitive 
apprehension of all those that are absolutely simple, 
attempt to ascend to the knowledge of all others by 
precisely similar steps; ** and further, ''If we wish our 
science to be complete, those matters which promote 
the end we have in view must one and all be scrutinised 
by a movement of thought which is continuous and 
uninterrupted. 'J For this, Descartes says, it is necessary 
p' to run over the different propositions from time to time7 
Tceeping the imagination moving continuously in such a 
way that while it is intuitively perceiving each fact it 
simultaneously passes on to the next; and thus I would 
do until I had learned to pass from the first to the last so 
quickly, that no stage in the process was left to the care 

xvi Discourse on Method 

of the memory, but / seemed to have the whole in intuition 
before me at the same time/*_\ 

Such is Descartes' mathematical method. It implies, 
as we have seen, a clear distinction between the under- 
standing and the senses or imagination, and if we are to i 
practise it we must realise for ourselves the essential 
difference between the clear and distinct apprehension., 
of the understanding and the obscure light of the senses. 
We must turn our backs on the vague and obscure and 
accustom ourselves to the apprehension of simple and 
self-evident truth. " We ought to give the whole of our 
attention to the most insignificant and most easily 
mastered facts, and remain a long tune in the contempla- 
tion of them until we are accustomed to behold the truth 
. clearly and distinctly. . . . Every one ought therefore 
^^ to accustom himself to grasp in his thought at the same 
I time facts that are at once so few and so simple that he 
1 shall never believe that he has knowledge of anything 
1 which he does not mentally behold with a distinction 
\ equal to that of the objects which he knows most 
\ distinctly of all." 

This advice naturally led to the Cartesian method of 
doubt. ^FoT when Descartes came to survey our beliefs 
and jtheories about the world he found in them none of 
that certainty which is so striking in mathematics. The 
only thing to be done was to reject everything that was 
merely probable, for between the probable and the 
^ mathematically certain there is no relation, and to get 
back to the certain and self-evident. " Not that in this 
I imitated the sceptics, who doubt only that they may 
doubt and seek nothing beyond uncertainty itself; for 
on the contrary, my design was singly to find ground of 
assurance, and cast aside the loose earth and sand that 
I might reach the rock or the clay." 

Now in mathematics this distinction so much insisted 
upon is essential, but when we come to our knowledge 
of the concrete world of existence, certain difficulties 
present themselves if we attempt to maintain it. Is it 
possible there so to dispense with the senses ? However 
mathematical we make our inquiries, must they not start 
with some basis of mere observation ? In other words 


Introduction xvii 

mathematics, doe s no t conce rn itself with the question 
of existence, but only with universal implications^ How 
is there any^'possibility'bf arrivirig~at~cOnclusions~^s'tb 
what actually exists wMch " shaTPKave mathematical 
certainty? Descartes in his metaphysics is concerned 
almost solely with this problem of existence, and with 
(the impossible attempt to disengage the question of 
what exists as distinguished from what is true from any 
dependence on the senses. If we are to have knowledge 
of the existing world, we must find something of whose 
existence we are certain, and then show that all other 
things whose existence we assert are dependent upon 
thisT" Descartes professes in this merely to be applying 
tiie mathematical method to other inquiries, but that 
that method is inapplicable to problems involving 
existence is evident when we come to examine the actual vT 
nature of his metaphysical arguments. In the mathe- 
matical method the mind apprehended various pro- 
positions, each of which was its own evidence. Further, 
intuition led to apprehension of the relation between ^ 
these propositions, but did nothing to make their truth *^ 
more certain. In the metaphysics a certain principle 
is reached, I Mnk, therefore I_am^^^ 
basis of all the rest, which are representedLj^jieducible 
from ijt. The test of truth is riolonger clear and distinct 
conception, but dependence on an ultimate proposition. 
This is not the mathematical method as originally 

Further, we find in these arguments use made of certain 
conceptions, such as substance and its modes or cause 
and effect, which apply to existences, and not to truths 
or propositions, and yet the relation between substance 
and its modes, or between cause and effect, is conceived 
of as a mathematical relation. The distinction between" 
what is true and what exists, or knowledge and reality, 
is ignored till the concrete world of existence becomes 
a system of mathematical implications and nothing more, 
and the concrete individual self becomes merely that 
which thinks. '* Quantity and number,*' says Descartes 
finally, ** differ only in thought from that which has 
quantity and is numbered." Yet at the same time the 





Discourse on Method 


crucial argument for existence— whether the existence 
of the self or of God or external reality— are arguments 
which could not apply to "quantity or number/' but 
only to "what has quantity and is numbered/' or to 
>vhat counts and numbers. 

Further, the resolution to ignore the probable means 
the ignoring of the data of the senses, and that means 
that while we can get back to the certainty of existence 
in general, we can have no knowledge of the individual. 
For the real world is conceived as purely mathematical 
and without individuality. It becomes increasingly 
fdifi&cult to understand not simply what is the relation 
\ between knowledge and perception, but how there is 
J any room for the senses at all. 

^^These difficulties are apparent in Descartes' account 
of the method of doubt, which is given at greatest length 
in the first and second meditations. He begins by 
noticing the illusions of the senses, the changing nature 
of their objects, and the difficulty caused by the existence 
of dreams. The general conclusion which these con- 
siderations support is that no individual judgment of 
the form: This or that thing, having such and such 
qualities, exists: can have perfect theoretic certainty. 
Any one of these may be doubted. Therefore, Descartes 
argues, they may all be doubted and for his purposes 
ignored. Nevertheless we still have the existence of 
doubt and hence of a doubter, and may conclude, I 
think, or I doubt, and therefore I am. Here Descartes 
finds his desired certain foundation on which all other 
V. knowledge is to rest. 

Now it must be observed that this argument proves 
at once too little and too much. It proves too little, 
because thinking and doubting, being transitive verbs, 
must have some object. Each judgment we make 
about individual things may be doubted; we may also 
doubt whether things have the separateness which they 
seem to have; but we cannot doubt — to take the argu- 
ment on its lowest terms — that there is something there. 
Our thought may be and is independent of each separate 
object, but it cannot be independent of objects altogether. 
If no objects were presented to our senses, we should have 

Introduction xix 

nothing to think about, and there would be no thought. 
But Descartes wrongly uses the argument to conclude 
that mind is wholly independent of and exists entirely 
apart from body, j^' I thence concluded that I was a 
substance whose whole essence or nature consists only in 
thinking, and which, that it may exist, has need of no 
place, nor is dependent on any material thing: so that 
■' I,' that is to say, the mind by which I am what I am, 
is wholly distinct from the body and 'is even more easily 
known than the latter, and is such, that although the 
latter were not, it would still continue to be all that 
it is."7 

This is the foundation of the Cartesian idealism which 
has had such a fatal influence on modem theories of 
knowledge. It is based on the misconception that the 
mind knows itself more easily or more certainly than it 
knows objects. But while the existence of mind is a 
presupposition of our knowledge of objects, objects to 
be known are equally a presupposition of the existence of 
mind. Further, if the mind knowing itself is made our 
starting-point for deductions, there is no possibility of 
getting beyond the mind or explaining how we ever 
came to suppose that there is anything external to the 
mind to be known. 

The argument also proves too much, as is seen when 
we consider what Descartes means by ** I." For what 
is really implied in the fact of doubting is a subject that 
doubts. Descartes assumes without proof that a subject 
that doubts must have personal identity, or must be 
what he calls a substance. He implies that what doubts 
at one moment must be the same as that which doubts 
at another. But the unity of the self which this implies, 
as Locke and Hume afterwards pointed out, depends 
upon memory, and memory, Descartes insists, gives only 
probability. The apparent force of the argument lies in 
the contrast between the consciousness of self-identity 
and the variety and mutability of the objects of thought. 
But as there would be no thinking if there were no 
objects, so there would be no unity of thought, and hence 
no personality, were there not unity and permanence in 
the objects of thought. 

XX Discourse on Method 

^--^^Descartes had reached an intuitive certainty of 
/ existence at the price of entirely cutting off thought from 
/ its objects. That sharp separation made, he has to 
"overcome the difficulty of getting back to the world 
of external objects again. Starting with the certainty 
of the existence of a mind independent of all non-mental 
reality, he examines the mind and shows that as mind 
it is not self-sufficient. This leads him to a statement, 
not of the existence of non-mental reality, but of the 
existence of a mind on which our mind is dependent, 
in other words, the existence of God. From the existence 
of God Descartes further argues the existence of external 
reality. His proofs of the existence of God, therefore, 
are important in his system not only in themselves, but 
as bridging over the gulf he has made between the self 
and its objects. 

It is impossible in short space properly to examine 
Descartes' proofs of the existence of God. It is enough 
to notice that they depend upon the essential insufficiency 
of the individual mind if it is taken in isolation from the 
world, but that isolation, as we have seen, has only been 
determined by a fallacy. The force of the arguments 
really lies in the impossibility of the conclusion which 
Descartes had extracted from I think, therefore I am. 
The independent isolated self presupposed in that 
conclusion turns out to be limited and imperfect, to 
imply, therefore, a not-self; and in an argument which 
confuses the notion of theoretic self-sufficiency with 
moral perfection, the not-self is identified with God as 
He is conceived by religion. All that the ontological 
argument will prove is the existence of a reality inde- 
pendent and external to mind. But that can give no 
proof of the existence of God which is worth having, 
unless we can also show that that reality is moral, and 
that, as Kant pointed out, cannot be proved by any 
purely intellectual argument. 

The argument by which Descartes from the existence 
of God infers the existence of the external world is 
superficially a glaring petitio principii. For he confuses 
the issue by supposing that we may be deceived in 
thinking that what we clearly and distinctly conceive 

Introduction xxi 

is true, and can only get rid of this supposition by argu- 
ing that it is incompatible with the goodness of God to 
suppose that He would so deceive us. But if what we 
clearly and distinctly conceive is not true, then Descartes 
cannot prove the existence of God, and there is no 
refuge from scepticism. This is an unfortunate de- 
clension from his fundamental and sound position that 
there are some truths which are their own evidence. 
But there is more in the argument than this. Descartes 
uses the existence and the trustworthiness of God to 
prove not the truth of mathematics, but the existence 
of mathematical objects. Thus we get back at last to 
the existence of the external world. 

This return to the external world is possible only 
under conditions which determine Descartes' view of 
reahty. The trustworthiness of God cannot be called 
in to establish the existence of what our senses perceive. 
For obviously our senses often deceive us. Descartes, 
therefore, maintains that our senses do not give us truth 
at all. They are only meant to serve us for practical 
purposes, not to give us knowledge. They lead us into 
error only because we do not accept the limitations which 
God has put upon them. The trustworthiness of God 
warrants our believing in the existence of what we 
clearly and distinctly conceive, since here error is im- 
possible ; that is, it warrants the existence of our mathe- 
matical conceptions. This is the basis of Descartes' 
belief in that external reaUty is of a purely mathematical 
nature. /'*' I at least know with certainty that such 
things niay exist, in as far as they constitute the object 
of the pure mathematics, since, regarding them in this 
aspect, I can conceive them clearly and distinctly." 

Descartes begins his account of external reality by 
distinguishing between the primary and secondary 
quahties of objects. The secondary qualities, being sense 
data and essentially vague and obscure, cannot have 
real existence. Reality then is described as pure 
extension and identified with space. '* Space or in- 
ternal place, and the corporeal substance which is com- 
prised in it, are not different in reality but merely in 
the mode in which they are wont to be conceived by us. 

xxii Discourse on Method 

Nothing remains m the idea of body, except that it is 
something extended in length, breadth, and depth; and 
this somethmg is comprised in our idea of space, not 
only of that which is full of body, but even of what is 
called void space." 

Here we find the full consequences of Descartes 
separation of mind from its objects. As mind is regarded 
by him as pure thought, unextended and separate from 
body and all that pertains to the body, so matter, its 
counterpart, is pure extension devoid of any qualities 
except such as are involved in the nature of extension. 
The argument by which this conclusion has been reached 
assumes that because what is distinctly and clearly 
conceived is true, therefore nothing which is not clearly 
and distinctly conceived can exist, a conclusion which 
the premiss does not warrant. Descartes by reaching 
external existence through God has really identified the 
object of mathematical thought with reality. 

The process of disentangling this confusion was begun 
by the English empiricists and completed by Kant. It 
would take too long to follow it out here. But some- 
thing must be said about the impossibilities of Descartes' 
identification of external reahty with extension. 

If there is no distinction between space and objects 
in space, if the qualitative differences in objects revealed 
by the senses are unreal, and external reality is mere 
quantity, then it is impossible to distinguish between 
reality and blank nothing. Empty space separated 
from the objects in space is nothing, and if body and 
space are the same, empty space filled with empty space 
is no more real. Descartes to some extent sees this 
difficulty, and supposes that differences in extension are 
made possible by motion, anticipating the doctrine 
which has been the basis of much science, that all reaUty 
is nothing but extension and motion. But this makes it 
incumbent upon him to explain what motion is, and 
in his premisses he is bound to conceive motion in its 
turn as nothing but extension. For motion can only 
be clearly and distinctly conceived in terms of the space 
which it traverses. For the forms in which motion 
manifests itself as force, pressure, or weight are described 

Introduction xxiii 

by Descartes as secondary qualities, and therefore un- 
real. Descartes sometimes distinguishes between ex- 
tension and motion, thus saving the differences in reality 
at the expense of adding a third entity whose relation 
to either extension or mind is as mysterious as the 
relation of either of these to the other, and at other 
times asserts that motion is but a mode of extension, 
which leaves reality again incapable of differentiation. 

One last point must be noticed. Reality being 
identified with extension, it becomes impossible for 
Descartes to explain the reaHty of time. He makes 
the existence of duration a proof of the existence of God 
{Principles, Part I. XXI.), because duration can only be 
explained by a continuous miracle. Duration is some- 
thing which cannot be clearly and distinctly conceived 
in Descartes' sense. This is of interest to-day in that the 
philosophy of Bergsen starts with the inadequacy of the 
scientific theory of reality to explain change, time, and 
motion, and the full force of the theories which he is 
criticising, and which he asserts to be the basis of much 
modem scientific thinking, can best be studied in 
Descartes, who was their first author. 


January 1912. 


Single Works. — Discours de la Methode, la Dioptrique, les 
Meteores, la Geometrie (Leyden), 1637; reprinted without la 
Geometrie, and with la Mecanique, la Musique (Paris), 1724; Latin 
edition (Amsterdam), 1644; Meditations Metaphysiques (published 
as Meditationes de Prima Philosophia in Paris), 1641; (Amster- 
dam), 1642; Objections contre les Meditations, avec les R6ponses 
(Paris), 1641; (Amsterdam) 1642; Lettre de Rene Descartes k 
Gisbert Voet (published as Epistola Renati Descartes ad Gisbertum 
Voeitum in Amsterdam), 1643; Les Principes de la Philosophic 
(pubUshed as Principia Philosophias in Amsterdam), 1644; Les 
Passions de TAme (Amsterdam), 1650; Le Monde, ou Traite de la 
Limiiere (Paris), 1664, 1677; L' Homme (translated into Latin, and 
first appeared as Renatus Descartes de Homine), 1662, 1664; re- 
printed 1677, 1729; De la Formation du Foetus, 1664; Lettres de 
1629-1648, ed. by C. Clerselier (Paris), 1657, 1667; Regies pour la 
Direction de 1' Esprit, Recherche de la Verite par les Lumidres 
Naturelles (first appeared in Opera Posthuma Cartesii in Amster- 
dam), 1701. 

xxiv Discourse on Method 

Collected Editions. — Opera (Latin ed. in Amsterdam), 1650 
8 vols., 1670-1683; OEuvres Completes, ed. by Victor Cousin, 11 
vols. (Paris), 1824- 1826; CEuvres Philosophiques, ed. by A. Garnier, 
4 vols. (Paris), 1834; CEuvres Completes, ed. by Chas. Adam and 
Paul Tannery (Paris), 1897; Philosophical Works of Descartes 
ed. by Eliz. S. Haldane and G. R. T. Ross, 1911, etc. 

English Translations. — R. Descartes' Excellent Compendium 
of Musick, by Lord Brouncker, 1653 ; Discourses of the Mechanicks, 
by T. Salusbury, 1661 ; Discourse on Method, by Prof. John Veitch, 
1850; Meditations, and Selections from the Principles of Philosophy, 
by Prof. John Veitch, 1853; Meditations, by R. Lowndes, 1878; 
Rules for the Direction of the Mind, The Meditations (in part), 
The World, Passions of the Soul, etc., by H. A. P. Torrey, 1892; 
Discourse on Method, and Metaphysical Meditations, by Gertrude 
B. Rawlings, 1901 ; Philosophical Works, by Eliz. S. Haldane and 
G. R. T. Ross, 1911, etc. 

Life. — La Vie de M. Descartes, by V. A. Baillet, 1691; Eloge, 
by A. L. Thomas, 1765; Sa Vie et ses Travaux, by J. Millet, 1867; 
Descartes, by J. P. Mahaffy, 1880; Descartes and His School, b 
Kuno Fischer (English translation), 1887; Descartes, by A. Fouille 
1893; Descartes, Spinoza, and the New Philosophy, by J. Iverach 
1904; His Life and Times, by Eliz. S. Haldane, 1905. 


Discourse on the Method of Rightly Conducting the 

Reason and Seeking Truth in the Sciences . . i 

Meditations on the First Philosophy: — 

Dedication ....... 

Preface ........ 

Synopsis of the Meditations .... 

I. Of the Things of which we may Doubt 

II. Of the Nature of the Human Mind; and that it is 
more easily known than the Body 

III. Of God: that he exists .... 

IV. Of Truth and Error 

V. Of the Essence of Material Things; and, again, of 
God: that he exists .... 








VI Of the Existence of Material Things, and of the 
Real Distinction between the Mind and Body 
of Man ..... . 127 

The Principles of Philosophy: — 

Preface ......... 147 

Dedication . . . . . . . - 162 

I. Of the Principles of Human Knowledge . .165 

II. Of the Principles of Material Things. Sects, i. 

to XXV. ....... 199 

III. Of the Visible World. Sects, i. to iii. . . 212 

IV Of the Earth. Sects, i. to xix. . .- . . 214 




Appendix: — 


Demonstrations of the Existence of Deity . . .229 

Notes by the Translator: — 

I. Perception 239 

II. Idea .... 

. 241 

III. Objective Reality . 

• 249 

IV. From or Through the Senses 

. 249 

V. Thought .... 

. 250 

VI. Innate Ideas . 

. 250 

VII. Formally and Eminently . 

. 252 

VIII. Pure Intellection 

• 253 

IX. Motion 

• 253 

X. Second Element 

. 254 









If this Discourse appear too long to be read at once, 
it may be divided into six parts: and, in the first, will 
be found various considerations touching the Sciences; 
in the second, the principal rules of the Method which 
the Author has discovered; in the third, certain of the 
rules of Morals which he has deduced from this Method; 
in the fourth, the reasonings by which he establishes 
the existence of God and of the Human Soul, which are 
the foundations of his Metaphysic; in the fifth, the 
order of the Physical questions which he has investi- 
gated, and, in particular, the explication of the motion 
of the heart and of some other difficulties pertaining 
to Medicine, as also the difference between the soul of 
man and that of the brutes; and, in the last, what the 
Author believes to be required in order to greater ad- 
vancement in the investigation of Nature than has yet 
been made, with the reasons that have induced him to 


Good sense is, of all things among men^ tligjngiSLfiqugJly 
J istribute 3T for ^veiyp^^ thinks himself so abundantly 
provided^ with _ it, that those even who are the most 
difficult to satisfy in everything else, do not usually 
desire a larger measure of this quality than they already 
possess. And in this it is not likely that all are mistaken: ' 
the conviction is rather to be held as testifying that the 
power of judgi ng: arig^h t and of distinguishinp; truth fro m 
exror^ which i.r pmppTtv wlm-l-^ts" railed P^^od sense or 
i:;easoru is by nature equal in all men; and that the -y^ 
diversity of our opinions, consequently_^Ldojes-not--arise 
from some being endowed with a larger ^^hare^qf^ reason 
than others, but solely from this, that we conduct" our 
thoughts along different ways^ and dojiot4ix~our_attention 
on the same objects. For to be possessed of a vigoro us/ ^^ 
mind is not eno ugh : the p rime requisi te is rightly to | / 
3 pp1y_ jl^ The greatest minds, as they are capable ^f 
the highest excellences, are open likewise to the greatest 
aberrations; and those who travel very slowly may yet 
make far greater progress^ provided they keep always 
to the straight road, than those who, while they run, 
forsake it. - 

For myself, I have never fancied my mind to be in 
any respect more perfect than those of the generality; 
on the contrary, I have often wished that I were equal 
to some others in promptitude of thoug ht, or i n clearness 
and distinctness of Tmagination , or in fulness anJ readiness 
otjaemoJ^I And besides these, I Icnow of no other 
qualities that contribute to the perfection of the min d: 
for as to the reason or sense, inasmuch as it is that alone 
which constitutes us men, and distinguishes us from 


4 Discourse on Method 

the brutes, I am disposed to believe that it is to be found 
complete in each individual; and on this point to adopt 
the common opinion of philosophers, who say that the 
difference of greater and less holds only among the 
accidents, and not among t\\Q forms or natures of individuals 
of the same species. 

I will not hesitate, however, to avow my belief that 
it has been my singular good fortune to have very early 
in life fallen in with certain tracks which have conducted 
me to considerations and maxims, of which I have formed 
a method that gives me the means, as I think, of gradually 
augmenting my knowledge, and of raising it by little and 
httle to the highest point which the mediocrity of my 
talents and the brief duration of my life will permit me 
to reach. For I have already reaped from it such fruits 
that, although I have been accustomed to think lowly 
enough of myself, and although when I look with the eye 
of a philosopher at the varied courses and pursuits of 
mankind at large, I find scarcely one which does not 
appear vain and useless, I nevertheless derive the highest 
satisfaction from the progress I conceive myself to have 
already made in the search after truth, and cannot help 
entertaming such expectations of the future as to believe 
that if, among the occupations of men as men, there is 
any one really excellent and important, it is that which I 
I have chosen. I 

/After all, it is possible I may be mistaken; and it is ' 
but a little copper and glass, perhaps, that I take for I 
gold and diamonds. I know how very hable we are 
to delusion m what relates to ourselves, and also how ' 
much the judgments of our friends are to be suspected 
when given m our favour. But I shall endeavour m this 
discourse to describe the paths I have followed, and to 
^Imeate my life as in a picture, in order that each one 
may l)e able to judge of them for himself, and that in the 
general opmion entertained of them, as gathered from 
current report I myself may have a new help towaVd^ 

oTr;^^?: "* '^'^ "• '"""^ ' ""^ i^™ i" *' "'S 

f wh ?^ h"S --^ ^j|!!:.^n^"- '' ^^^ t o teach the met hod 
1 wjncnjacli^ou^^ right conaS ^f his 

Discourse on Method 

re ason, but solely to describe the way in which I ha ve 'i^ 
e ndeavoured tg QQ]| ;\du(^'tr my nwn, I'hey who set them-f ' 
selves to give precepts must of course regard themselves 
as possessed of greater skill than those to whom they 
prescribe; and if they err in the slightest particular, 
they subject themselves to censure. But as this tract* 
is put forth merely as a history, or, if you will, as a tale, 
in which, amid some examples worthy of imitation, there 
will be found, perhaps, as many more which it were 
advisable not to follow, I hope it will prove useful to 
some without being hurtful to any, and that my openness 
will find some favour with all. 
--^From my childhood, I have been familiar with lette rs; 
and as I was given to believe that by their help a clear 
an d certain fenaw|<?dg^ ^^ pH tr^^t ^'" ^ useful iiT melnight 
be acquired, I was ardently desi rous o f iagtmclSH^ fiut 
as soon as I had finished the entire course of study, at the 
close of which it is customary to be admitted into the 
order of the learned, I com.pletely changed my opinion. 
For I found[inyself involved in so many doubts and errors, 
tha t TVas convinci^^^H^IadySioS^o fa^ in a ll 
"^y_ fttf^mpt'^ ^^ l^a^y^ nf i than t^ ^ ^^ discovery at eve ry 
turn ^ my own ignorance. And yet i" was studying^n 
one of the most celebrated schools in Europe, in which 
I thought there must be learned men, if such were any- 
where to be found. I had been taught all that others 
learned there; and not contented with the sciences 
actually taught us, I had, in addition, read all the books 
that had fallen into my hands, treating of such branches 
as are esteemed the most curious and rare. I knew the 
judgment which others had formed of me; and I did not 
find that I was considered inferior to my fellows, although 
there were among them some who were already marked 
out to fill the places of our instructors. And, in fine, our 
age appeared to me as flourishing, and as fertile in power- 
ful minds as any preceding one. I was thus led to take 
the liberty of judging of all other men by myself, and of 
concluding that t here was no science^in existen ce that was 
of such„ajriature ^ 1 had pr eviolisly^e enrgiven to ^e^^ 

I still continued, howeverTto nold in esteemTRe studies 
of the schools. I was aware that the languages taught 



6 Discourse on Method 

in them are necessary to the understanding of the writings 
of the ancients; that the grace of fable stirs the mind; 
that the memorable deeds of history elevate it; and, if 
read with discretion, aid in forming the judgment; Jthat 
the perusal of all excellent books is, as it were^J ojiiter- 
v iewwitlTt he noblest me n ot past ages, who nave written 
them, and even a studied Triterview, in which are dfs- 
cqyered to us only their choicest thoughts; that eloquence 
has incomparable force and beauty; that poesy has its 
ravishing graces and delights; that in the mathematics 
there are many refined discoveries eminently suited to 
gratify the inquisitive, as well as further all the arts and 
lessen the labour of man; that numerous highly useful 
precepts and exhortations to virtue are contained in 
treatises on morals; that theolo gy point s^out the path 
to heaven; that philosophy''~aSords the means of dis- 
courslft'g^with an appearance of truth on all matters, and 
commands the admiration of the more simple; that 
jurisprudence, medicine, and the other sciences, secure 
for their cultivators honours and riches; and, in fine, 
that it is useful to bestow some attention upon all, even 
upon those abounding the most in superstition and error, 
that we may be in a position to determine their real value, 
and guard against being deceivedy^ 

But I believed that I had already given sufficient time 
to languages, and likewise to the reading of the^^fficitings 
of the ancients, to their histories and fablesj For to 
/ hold converse with those ofother ages and to travel, are 
almost the same thing. It is~ useful t o know somethi ng 
of the manne rs of differejit" nMToftS, that we ma y be 
en aM | blO'''TU fUill'i djtnore correct judgment repcar ^mg our 
o wn~{'an(l be prey ^ ^nt^^ from thinKing that everyth ing 
c omrary to Qnr custoinsTs ridiculous and irration al, — a 
conclusion usually come to by those wKosc ex'perience 
has been limited to their own country. On the other 
ha nd, when too much time is occupied in ffiaiVelE ng, "we 
^5fffl"^^ /^^^^^5^^s to oiir ^native country; and thfi .over 
c arious in the customs oTthe past are g enerally ignorant 
oJ^Q se .pj tthfi r^^^nrit Besides, fictitious narratives 
ImTus to imagine the possibility of many events that are 
impossible; and even the most faithful histories, if they 


Discourse on Method 7 

do not wholly misrepresent matters, or exaggerate their 
importance to render the account of them more worthy of 
perusal, omit, at least, almost always the meanest and 
least striking of the attendant circumstances; hence it 
happens that the remainder does not represent the truth, 
and that such as regulate their conduct by examples 
drawn from this source, are apt to fall into the extrava- 
gances of the knight-errants of romance, and to enter- 
tain projects that exceed their powers. 

I esteemed eloquence highly, and was in raptures with 
poesy; hiit J t>>nnght that hath wprf^ orift.g of nature 
raj:h er than iruit&-^-^tiid:v. Those in whom the faculty 
of reason is predominant, and who most skilfully dispose 
their thoughts with a view to render them clear and intel- 
ligible, are always the best able to persuade others of the 
truth of what they lay down, though they should speak 
only in the language of Lower Brittany, and be wholly 
ignorant of the rules of rhetoric; and those whose minds 
are stored with the most agreeable fancies, and who can 
give expression to them with the greatest embellishment 
and harmony, are still the best poets, though unacquainted 
with the art of poetry. 

> I was especially delighted with the mathematics, on 
account of the certitude and evidence of their reason- 
ings; but I had not as yet a precise knowledge of their 
true use; and thinking that they but contributed to the 
advancement of the mechanical arts, I was astonished 
that foundations, so strong and solid, should have had 
no loftier superstructure reared on them. On the other 
hand, I compared the disquisitions of the ancient moralists 
to very towering and magnificent palaces with no better 
foundation than sand and mud: they laud the virtues 
very highly, and exhibit them as estimable far above 
anything on earth; but they give us no adequate 
criterion of virtue, and frequently that which they 
designate with so fine a name is but apathy, or pride, 
or despair,jor_£arri£ide- 

I revered our theology, and aspired as much as any 
one to reach heaven: but being given assuredly to under- 
stand that the way is not less open to the most ignorant 
than to the most learned, and that the revealed truths 

8 Discourse on Method 

which lead to heaven are above our comprehension, I did 
not presume to subject them to the impotency of jny 
reason; and I thought that in order competently to 
undertake their examination, there was need of some 
special help from heaven, and of being more than man. 

Otjibilosophy I will say nothing, except that when I 
saw that it had been cultivated for many ages by the 
most distinguished men, and that yet there is not a 
single matter within its sphere which is not still in dis- 
pute, and nothing, therefore, which is above doubt, I 
did not presume to anticipate that my success would be 
greater in it than that of others; and further, w jien I 
c onsidered the number of conflicting opinio ns touching 
a smgle^ lnalte^^^^ ^^ Be uphela pvTeamed men, 

while therie' can Be b^ ^^ true, I reckoned as well -nigh 


AS t6 IKe otEer sciences, inasmuch as these borrow 
their principles from philosophy, I judged that no solid 
superstructures could be reared on foundations so infirm; 
and neither the honour nor the gain held out by them 
was sufficient to determine me to their cultivation: for 
I was not, thank Heaven, in a condition which compelled 
me to make merchandise of science for the bettering of 
my fortune; and though I might not profess to scorn 
glory as a cynic, I yet made very slight account of that 
honour which I hoped to acquire only through fictitious 
titles. And, in fine, of false sciences I thought I knew 
the worth sufficiently to escape being deceived by the 
professions of an alchemist, the predictions of an 
astrologer, the impostures of a magician, or by the 
artifices and boasting of any of those who profess to 
^ know things of which they are ignorant. 

^For these reasons, as soon as my age permitted me to 
jmss from under the control of my instructors, I entirely 
abandoned the study of letters, and rPf;n1y^|^ ^r^ ]^^^^r to 
seek anv other sci ence than the knowledp;e of myse lf. 

or Qt the frresi^l hnn\r nf fh^ .yn^r-}A T .p^^^ ||^^ ^^^^^j^i^P^ 

of my youth in travelling, in visiting courts and armies, 
m holding intercourse with men of different dispositions 
and ranks, in collecting varied experience, in proving 
myself in the different situations into which fortune threw 

Discourse on Method TfH^^^^T^i^ 

me, anH, ahnyp. a]\ in m^kinp; sncb j{^er±iQi] ^ialIie jQ3atter 

Of jnv exp^ rirnrf P^ ^^ ^PmrP ^^y ^'ijip^nvprnpnl- For it 

occurred to me that I should find much more truth in ~^^ 
the reasonings of each individual with reference to the 
affairs in which he is personally interested, and the issue of 
which must presently punish him if he has judged amiss, 
than in those conducted by a man of letters in his study, , 
regarding speculative matters that are of no practical i 
moment, and followed by no consequences to himself, 
farther^ perhaps, than that they foster his vanity the 
better the more remote they are from common sense; 
requiring, as they must in this case, the exercise o£. 
greater ingenuity and art to render them probable. /in 
addition, I had always a most earnest desire tn knnw feygy I 
to disLiil UUllJBL the, true from t \?V^ ffll^^, m nrrier t,hftt, I \ 

mi^ttT'^e'abl e clearly to discriminate the right path in * 
li fe, and proceed in it wittl confldenceTT 
"^t is true that, while busied only^in considering the 
manners of other men, I found here, too, scarce any 
ground for settled conviction, and remarked hardly less 
contradiction among them than in the opinions of the 
philosophers. So that the greatest advantage I derived/ 
fr om the s t^dy cQ3gtStgd^irrtl!ltertlial^ many 

things which, how ever extravagant and ridiculous to 
o uF"appre'!i'eft5l6ti. are y^t by common consent receiv ed 
anjd approved by other great nations, i learnea to ente r- 
t ain toooecidecl a oeliei m regard to nothing ot the tru th 
of which J J if^fl been persnaaed merely by example a nd 
custom ; and tTius T"graclualiy extricated myself from 
many errors powerful enough to dairken our natural 
intelligence, and incapacitate us in great measure from 
listening to reason. But after I had been occupied 
several years in thus studying the book of the world, and in 
essaying to gather some experience, I at length resolved 
to make myself an object of study, and to employ all the 
powers of my mind in choosing the paths I ought to follow^ 
an undertaking which was accompanied with greater 
success than it would have been had I never quitted my 
country or my books. 


I WAS then in Germany, attracted thither by the wars in 
that country, which have not yet been brought to a 
termination; and as I was returning to the army from 
the coronation of the emperor, the setting in of winter 
arrested me in a locaUty where, as I found no society to 
interest me, and was besides fortunately undisturbed by 
any cares or passions, I remained the whole day in 
seclusion,^ with full opportunity to occupy my attention 
with my own thoughts./Of these one of the very first 
that occurred to me was, that there j^ ^^^^^ri; ^^ Tnnrh 
p erfection in works r^n ipr^^^^ of ^^^y ?=pppyptp. parts, 
up on wii ich Qitterenr iiflprls ha^ been empioved. ^s^in 
those completed by a ^ jngle ^master. Thus it is observ- 
able thaTTKe" Buildings which a single architect has 
planned and executed, are generally more elegant and 
commodious than those which several have attempted 
to improve, by making old walls serve for purposes for 
which they were not originally built. Thus also, those 
ancient cities which, from being at first only villages, 
have become, in course of time, large towns, are usually 
but ill laid out compared with the regularly constructed 
towns which a professional architect has freely planned 
on an open plain; so that although the several buildings 
of the former may often equal or surpass in beauty those 
of the latter, yet when one observes their indiscriminate 
juxtaposition, there a large one and here a small, and the 
consequent crookedness and irregularity of the streets, 
one is disposed to allege that chance rather than any 
human will guided by reason must have led to such an 
arrangement. And if we consider that nevertheless there 
have been at all times certain officers whose duty it was 
to see that private buildings contributed to public orna- 
ment, the difficulty of reaching high perfection with but 
1 Literally, in a room heated by means of a stove. — Tr. 


Discourse on Method 1 1 

the materials of others to operate on, will be readily 
acknowledged. In the same way I fancied that those 
na^iqnsjvvhich, starti a semi-barbarous state and .. 

advancing to civilisation by slow degrees^ have had their 
laws successively determined, and, as it were, forced 
upon them simply by experience of the hurtfulness of 
particular crimes and disputes, would by this process ; 
come to be possessed of less perfect institutions than 
those which, from the commencement of their association ^ 
as communities, have followed the appointments of some 
wise legislator. It is thus quite certain that the constitu- 
tion of the true religion, the ordinances of which are 
derived from God, must be incomparably superior to that 
of every other. And, to speak of human affairs, IJDelieve 
til?:?. J^.?--P-^-3t pre-eminence of Sparta was dij.e not to"tHe 
goodness of each of its laws in particular, for many of 
these^were very strange, and even opposed to good 
morals! but to the circumstance that, originated by a 
single individual, Jjiigy, alj^ tended tp.^a In 

fHe same wa y J thought that the sc iences co ntained in 
bo oks (su ch orthem at least as are m^aclellp ofprobaBle 

rp'^t;nn i ngT ' ^nfKrn tT f] ptti nn ^ir^ rrnn qj ^mpnTc^p.^ .,as they 

are of the opinions of many differentjn dividual^,. massed 
to geHier, are ^t t fa^r r'pmnvec^ ^rom truth than the simple 
inf erences which a ma n of good sense. u siQg..iiis„..Qaturgil 
an d unpr ejiidiced jud fflrnen clraw s respecting the j^aJbtexs 
of his experience. And becausF'weTiave all to pass 
through a 'StactF of infancy to manhood, and have been 
of necessity, for a length of time, governed by our desires 
and preceptors (whose dictates were frequently con- 
flicting, while neither perhaps always counselled us for 
the best), I farther concluded that it is almost impossible 
that our judgments can be so correct or solid as they 
would have been, had our reason been mature from the 
moment of our birth, and had we always been guided 
by it alone. 

It is true, however, that it is not customary to pull 
down all the houses of a town with the single design of 
rebuilding them differently, and thereby rendering the 
streets more handsome; but it often happens that a 
private individual takes down his own with the view of 

12 Discourse on Method 

erecting it anew, and that people are even sometimes 
constrained to this when their houses are in danger of 
falHng from age, or when the foundations are insecure. 
With this before me by way of example, I was persuaded 
that it would indeed be preposterous for a private indi- 
vidual to think of reforming a state by fundamentally 
changing it throughout, and overturning it in order to 
set it up amended; and the same I thought was true of 
any similar project for reforming the body of the sciences, 
or the order of teaching them established in the schools: 
but as for the opinions which up to that time I had 
embraced, I thought that I could not do better than 
^ resolve at once to sweep them wholly away, that I might 
afterwards be in a position to admit either others more 
s^ correct, or even perhaps the s^me when they had under- 
^ gone the scrutiny of reason. I firmly believed that in this 
way I should much better succeed in the conduct of my 
life, than if I built only upon old foundations, and leant 
upon principles which, in my youth, I had taken upon 
trust. For although I recognised various difficulties in 
this undertaking, these were not, however, without 
remedy, nor once to be compared with such as attend the 
slightest reformation in public affairs. T.fir gp. t^ ^ d i ^'^r ^^ 

once ovprthrnwn^ s\r^ ^i^h ffl-pf^j difficulty Sf fjt ^^p ^f^^'^j 
orsjeveiTKepFerect when once s eriously shaken, and the 
fall of siieh is always disastrous. Then if there are any 
imperfections in the constitutions of states (and that 
many such exist the diversity of constitutions is alone 
sufficient to assure us), custom has without doubt 
materially smoothed their inconveniences, and has even 
managed to steer altogether clear of, or insensibly 
corrected a number which sagacity could not have pro- 
vided against with equal effect; and^Jn ^ne, the def ects 
""--^are almo^^lways more tolerable tha^^^F^HgTneces- 
sary for their removal; in th^ ma nner that highw ays 

which isdndam£>ng- mountains, by beingjn y^li fregnent pdj 
becoriiia...gradua%^SQ sijiogth and commiqdiflUSr-thatjt is 
muchbetter to follow them than to seek a strai ghter p ath 
^™biii^ver the tops ^of rocks jndiJSgn^^ 
uottflms^otprecipiGes** ^ 

Hence it is that I cannot in any degree approve of 

Discourse on Method 1 3 

those restless and busy meddlers who, called neither by 
birth nor fortune to take part in the management of 
public affairs, are yet always projecting reforms; and if 
I thought that this tract contained aught which might 
justify the suspicion that I was a victim of such folly, 
I would by no means permit its publication. I have 
never contempl ated anythmg higher t han the reiorma- 
ti Qii 61 my own opinions^, and basmg them on a^iounQa - 
ti on whol ly my own. And although my own satisfaction 
witlTmyworETias led me to present here a draft of it, 
I do not by any means therefore recommend to every 
oiie^lse to^make a similar attempt. Those whom God 
has endowed with a larger measure of genius will enter- 
tain, perhaps, designs still more exalted; but for the 
many I am much afraid lest even the present undertaking 
be more than they can safely venture to imitate. The 
smgle design to jtrip one^s self ofallpast belief sjs one that 
oupST'nof'tonbe Jt^^ of 

mefi' Ts composed of two cIasses,~lor neither of which 
would this be at all a befitting resolution: in th^«ufrf4 
place, of those who with more than a due confidence in 
their own powers, are precipitate in their judgments and 
want the patience requisite for orderly and circumspect 
thinking; whence it happens, that if men of this class 
once take the liberty to doubt of their accustomed opinions, 
and quit the beaten highway, they will never be able to 
thread the byway that would lead them by a shorter 
course, and will lose themselves and continue to wander 
for life ; in the y»M4id place, of those who, possessed of 
sufficient sense or modesty to determine that there are 
others who excel them in the power of discriminating 
between truth and error, and by whom they may be 
instructed, ought rather to content themselves with the 
opinions of such than trust for more correct to their own 

For my own part, I should doubtless have belonged to 
the latter class, had I received instruction from but one 
master, or had I never known the diversities of opinion 
that from time immemorial have prevailed among men 
of the greatest learning. But I hnd brromo aw.irc, even 
so early as during my college life, that no o^.Qi9iLut<^w- 

14 Discourse on Method 

pvpr ?^h.qiir d and incredible, can be imagined, which has 
noi been maintained by someone^ot^tj^Il^ ; 

a n d ' afferwafds in the COll rse o r ' T nytravels I remarked| 
that all those whose opinions are decidedly repugnant to\ 
ours are not on that account barbarians and savages, but! 
on the contrary that many of these nations make an; 
equally good, if not a better, use of their reason than we 
do. I took into account also the very different character 
which a person brought up from infancy in France or 
Germany exhibits, from that which, with the same mind 
originally, this individual would have possessed had he 
lived always among the Chinese or with savages, and the 
circumstance that in dress itself the fashion which pleased 
us ten years ago, and which may again, perhaps, be 
received into favour before ten years have gone, appears 
to us at this moment extravagant and ridiculous. I was 
thus led to infer that the g round of our opinions is far 
mjore custom and examp l e than any_c f^<-^^" ff|n wlecl ge. 
And, hnaily,^IthougK such be the ground of our opinions, 
I remarked that a plurality of suffrages is no guarantee 
of truth where it is at all of difficult discovery, as in such 
cases it is much more likely that it will be found by one 
than by many. I could, however, select from the crowd 
no one whose opinions seemed worthy of preference, and 
thus I found myself constrained, as it were, to use my 
own reason in the conduct of my life. 
— ^yBut like one walking alone and in the dark, I resolved 
Xo proceed so slowly and with such circumspection, that 
if I did not advance far, I would at least guard against 
falling. I did not even choose to dismiss summarily 
any of the opinions that had crept into my belief without 
^ having been introduced by reason, but first of all took 
'^ sufficient time carefully to satisfy myself of the general 
nature of the task I was setting myself, and ascertain 
the true method by which to arrive at the knowledge of 
whatever lay within the compass of my powers. 

Among the branches of philosophy, I had, at an 
earlier period, given some attention to logic, and among 
those of the mathematics to geometrical analysis and 
algebra, — three arts or sciences which ought, as I con- 
ceived, to contribute something to my design. But, on 


Discourse on Method 15 

examination, I found that, as for logic, its syllogisms 
and the majority of its other precepts are of avail rather 
in the communication of what we already know, or even 
as the art of LuUy, in speaking without judgment of things 
of which we are ignorant, than in the investigation of the 
unknown; and although this science contains indeed 
a number of correct and very excellent precepts, there 
are, nevertheless, so many others, and these either 
injurious or superfluous, mingled with the former, that 
it is almost quite as difficult to effect a severance of the 
true from the false as it is to extract a Diana or a Minerva 
from a rough block of marble. Then as to the analysis 
of the ancients and the algebra of the moderns, besides 
that they embrace only matters highly abstract, and, to 
appearance, of no use, the former is so exclusively re- 
stricted to the consideration of figures, that it can exercise 
the understanding only on condition of greatly fatiguing 
the imagination; and, in the latter, there is so complete 
a subjection to certain rules and formulas, that there 
results an art full of confusion and obscurity calculated 
to embarrass, instead of a science fitted to cultivate the 
mind. By these considerations I was induced to seek 
some other method, which would comprise the advantages 
of the three and be exem^^pt from their defects. And as 
a multitude of laws often only hampers justice, so that 
a state is bes t governed whe n , with few l awf>, thf ?>p^re 
ri giQiy- lagXiStEterexaT m like^krmer, instead of the great 
number of precepts of whic ^logic js composed, I believed 
that the four following wouToprove perfectly sufficient 
for me, provided I took the firm and unwavering resolu- 
tion never in a single instance to fail in observing them. ^ 
Th e_^r^^ was neve r^o accept anything for t rue whi c h 
I did not clearly kno^W To'lE^s tfCh ; matTs to sav. carefull v 

, rTT i TTLl-umi i - i'i I ' — I trill 1 1 I I iii r i . J_" 'I 1 T - 

tp^Vgia' p fggipitancy and premdice, ana to comprise 
noTSng^ more^^m''Hw^ -judgment ~TO pyp.5^pn t pfl 

t(TnrnT'nyrr ^ ^^ gfi^^ ^ ^ ^ a nd-distinct ly-ft s- to -exclude all 

TI i"e*^^SS^5^-ta-dlvid£L..eacL,,D under ,,1 

jexa mihation Into as many parts as bossphle ^ anff as '^' 

m jgfi^ "^>f;^^^^^€€^s^^r y l or its a^ eauate-sd utixm: — r~- 

ThP fhjrd tn rnnfinrt my thoiigblgJiyg^i^h ordcr that, : . 

1 6 Discourse on Method 

by rnmmencing; with objects the simplest and easiest 
yn r ^/J ; T-r^ a;gSgq ^^ and liule^^nd, a s it 
^gTTtgk rrsi qK l u l lA(^Ki5 wfeye of the more-comp lex; 
^.3p^i=[ffr"fV.nii^l.t a rertain order ev en to those objects 
wTSegjOh^^T ov^ not stand in a relation of 

antficeie.nce aridj5,equehce ~~ 

And the last, in ev ery case to m,ak& . ^ nn^ ^^«1"^f^^^ so 
co mpfetc;~aiTdTevfe ^l£r^ that I might be assured 

that nothing wdS 6mWie^. 

-f^imgchsiins df SIThple and easy reasonings by means 
of which geometers are accustomed to reach the con- 
clusions of their most difficult demonstrations, had led 
me to imagine that ^11 thingc;^ tn the knowledge of which 
man i s competent, are mutuall y connectedin the same 
wayTgg; thai Jhere ^^^^ l ai i m TfT tr ^redJroin us 

I as t oETbey^d'our reach, or so hidden that we_ can not 
disc over it J ^r oyided nnjy we. gj^ m irom accepting '^ the 
falselST the true, and always .preserve in ^ii r th^"g^^° 
th e^ggerTnecessary for the deduction of one truth f rom 
anotherr"'And 1 had little ditfaculty in determining the 
oGJl^ with which it was necessary to commence, for 
I was already persuaded that it must be with the simplest 
and easiest to know, and, considering that of all those 
who have hitherto sought truth in the sciences, the mathe- 
maticians alone have been able to find any demonstra- 
tions, that is, any certain and evident reasons, I did not 
doubt but that such must have been the rule of their 
investigations. I resolved to commence, therefore, with 
the expmination of the simplest objects, not anticipating, 
however, from this any other advantage than that to be 
found in accustoming my mind to the love and nourish- 
ment of truth, and to a distaste for all such reasonings 
as were unsound. But I had no intention on that account 
of attempting to master all the particular sciences com- 
monly denominated mathematics: but observing that, 
however different their objects, they all agree in consider- 
ing only the various relations or proportions subsisting 
among those objects, I thought it best for my purpose 
to consider these proportions in the most general form 
possible, without referring them to any objects in par- 
ticular, except such as would most facilitate the know- 

Discourse on Method 17 

ledge of them^ and without by any means restricting 
them to these, that afterwards I might thus be the better 
able to apply them to every other class of objects to 
which they are legitimately applicable. Perceiving 
further, that in order to understand these relations I 
should sometimes have to consider them one by one, 
and sometimes only to bear them in mind, or embrace 
them in the aggregate, I thought that, in order the better 
to consider them individually, I should view them as 
subsisting between straight lines, than which I could find 
no objects more simple, or capable of being more distinctly 
represented to my imagination and senses; and on the 
other hand, that in order to retain them in the memory, 
or embrace an aggregate of many, I should express them 
by certain characters the briefest possible. In this way 
I believed that I cQ^dJiQrip3¥.^]i :that,w^^ 
geometrical analysis and in algg bra, and .cgrx^ct alLthe 

And, in point of fact, the accurate observance of these 
few precepts gave me, I take the liberty of saying, such 
ease in unravelling all the questions embraced in these 
two sciences, that in the two or three months I devoted 
to their examination, not only did I reach solutions of 
questions I had formerly deemed exceedingly difficult, 
but even as regards questions of the solution of which 
I continued ignorant, I was enabled, as it appeared to me, 
to determine the means whereby, and the extent to which, 
a solution was possible; results attributable to the circum- 
stance that I commenced with the simplest anfl mpst 
gen eral truth?7 a nd lliat ll icrSTgEclTtruth dScQ^ered was 
a r ule av_a ilable in the discoveng_jDf subs egueni^^^^Q 
Nor in this perhaps shall I appear too vain, if •it be con- 
sidered that, as the truth on any particular point is one, 
whoever apprehends the truth, knows all that on that 
point can be known. The child, for example, who has 
been instructed in the elements of arithmetic, and has 
made a particular addition, according to rule, may be 
assured that he has found, with respect to the sum of the 
numbers before him, all that in this instance is within 
the reach of human genius. Now, in conclusion, the 
method which teaches adherence to the true order, and 


1 8 Discourse on Method 

an exact enumeration of all the conditions of the thing 
sought includes all that gives certitude to the rules of 

But the chief ground of my satisfaction with this 
method, was the assurance I had of thereby exercising 
my reason in all matters, if not with absolute perfection, 
at least with the greatest attainable by me: besides, I 
was conscious that by its use my mind was becoming 
gradually habituated to clearer and more distinct con- 
ceptions of its objects; and I hoped also, from not having 
restricted this method to any particular matter, to apply 
it to the difficulties of the other sciences, with not less 
success than to those of algebra. I should not, however, 
on this account have ventured at once on the examination 
of all the difficulties of the sciences which presented 
themselves to me, for this would have been contrary to 
the order prescribed in the method, but observing that 
the knowledge of such is dependent on principles borrowed 
from philosophy, in which I found nothing certain, I 
thought it necessary first of all to endeavour to establish 
its principles. And because I observed, besides, that an 
inquiry of this kind was of all others of the greatest 
moment, and one in which precipitancy and anticipation 
in judgment were most to be dreaded, I thought that 
I ought not to approach it till I had reached a more 
mature age (being at that time but twenty-three), and had 
first of all employed much of my time in preparation for 
the work, as well by emdicating from my niiiu] iill Mir 
egoneous^^opim^ to thflt .momrnt. ftorrpted, 

as bjTarQassij Qg^ variety of pvp^ppnrp fn ^ff^^fl rna^f^n-gic 
for my reasonm gs, and by continually exercisingr m y.gplf 
injiijL£hosea^ ethod witli a view to increased skiU Jn its 


And, finally^ as it is not enough, before commencing 
to rebuild the house in which we Hve, that it be pulled 
down, and materials and builders provided, or that we 
engage in the work ourselves, according to a plan which 
we have beforehand carefully drawn out, but as it is 
likewise necessary that v/e be furnished with some other 
house in which we may live commodiously during the 
operations, so that I might not remain irresolute in my 
actions, while my reason compelled me to suspend my 
judgment, and that I might not be prevented from living 
thenceforward in the greatest possible felicity, I formed 
a provisory code of morals, composed of three or four 
maxims, with which I am desirous to make you acquainted. 
The Jirst wa,s to obey the laws and customs of my 
country, adhering firmly to the faith in which, by the 
grace of God, I had been educated from my childhood, 
and regulating my conduct in every other matter accord- 
ing to the most moderate opinions, and the farthest 
rgmoved from .extremes, which should happen to be 
adopted in practice with general consent of the most 
judicious of those among whom I might be living. For, 
as I had from that time begun to hold my own opinions 
for nought because I wished to subject them all to exami- 
nation, I was convinced that I could not do better than 
igllow in the meantime the opinions of the most judicious ; 
and although there are some perhaps among the Persians 
and Chinese as judicious as among ourselves, expediency 
seemed to dictate that I should regulate my practice 
conformably to the opinions of those with whom I should 
have to live; and it appeared to me that, in order to 
ascertain the re.d p_piniqns of such^ J ought rather to 
take cognisance of what they practised than of wliar 
they said, not only because,' m T;£e conTjptTo^^ 
manners, there are few disposed to speak exactly as they 


Discourse on Method 

believe, but also because very many are not aware of 
what it is that they really believe; for, as the act of mind 
by which a thing is believed is different from that by 
which we know that we believe it, the one act is often 
found without the other. Also, amid many opinions 
held in equal repute, I chose always the most moderate, 
as much for the reason that these are always the most 
convenient for practice, and probably the best (for all 
excess is generally vicious), as that, in the event of my 
falling into error, I might be at less distance fromlibe 
truth than if, having chosen one of the extremes, it should 
turn out to be the other which I ought to have adopgd. 
And I placed in the class of extremes especially all promises 
by which somewhat of our freedom is abridged; not 
that I disapproved of the laws which, to provide against 
the instability of men of feeble resolution, when what 
is sought to be accomplished is some good, permit engage- 
ments by vows and contracts binding the parties to 
persevere in it, or even, for the security of commerce, 
sanction similar engagements where the purpose sought 
to be realised is indifferent: but because I did not find 
anything on earth which was wholly superior to change, 
and because, for myself in particular, I hoped gradually 
to perfect my judgments, and not to suffer them to 
deteriorate, I would have deemed it a grave sin against 
good sense, if, for the reason that I approved of something 
at a particular time, I therefore bound myself to hold it 
for good at a subsequent time, when perhaps it had 
ceased to be so, or I had ceased to esteem it such. 

My second maxim was to be as firm and resolute in my 
actions as I was able, and not to adhere less steadfastly 
to the most doubtful opinions, when once adopted, than 
if they had been highly certain; imitating in this the 
example of travellers who, when they have lost their way 
in a forest, ought not to wander from side to side, far less 
remain in one place, but proceed constantly towards the 
same side in as straight a line as possible, without chang- 
ing their direction for slight reasons, although perhaps 
it might be chance alone which at first determined the 
selection; for in this way, if they do not exactly reach 
the point they desire, they will come at least in the end 

Discourse on Method 21 

to some place that will probably be preferable to the 
middle of a forest^/ln the same way, since in action it 
frequently happens that no delay is permissible, it is very 
certain that, when it is not in our power to determine 
what is true, we ought to act according to what is most 
probable; and even although we should not remark a 
greater probability in one opinion than in another, we 
ought notwithstanding to choose one or the other, and 
afterwards consider it, in so far as it relates to practice, 
as no longer dubious, but manifestly true and certain, 
since the reason by which our choice has been determined 
is itself possessed of these qualities. This principle was 
sufficient thenceforward to rid me of all those repentings 
and pangs of remorse that usually disturb the consciences 
of such feeble and uncertain minds as, destitute of any 
clear and determinate principle of choice, allow themselves 
one day to adopt a course of action as the best, which 
they abandon the next, as the opposite. 

-<9 My third maxim was to^endeavpur always to conquer 
myself rather than fortune, and change my desires rather 
than the order of the world, and in general, accustom 

■ myself to the persuasion that, except our own thoughts, 
there is nothing absolutely in our power; so that when 
we have done our best in respect of things external to us, 
all wherein we fail of success is to be held, as regards us, 
absolutely impossible :/and this single principle seemed 
to me sufficient to prevent me from desiring for the future 
anything which I could not obtain, and thus render me 
contented; for since our will naturally seeks those objects 
alone which the understanding represents as in some way 
possible of attainment, it is plain, that if we consider all 
external goods as equally beyond our power, we shall no 
more regret the absence of such goods as seem due to our 
birth, when deprived of them without any fault of ours, 
than our not possessing the kingdoms of China or Mexico; 
and thus making, so to speak, a virtue of necessity, we 
shall no more desire health in disease, or freedom in 
imprisonment, than we now do bodies incorruptible as 
diamonds, or the wings of birds to fly with. But I confess 
there is need of prolonged discipline and frequently 
repeated meditation to accustom the mind to view all 


2 2 Discourse on Method 

objects in this light; and I beheve that in this chiefly 
consisted the secret of the power of such philosophers 
as in former times were enabled to rise superior to the 
influence of fortune, and, amid suffering and poverty, 
enjoy a happiness which their gods might have envied. 
For, occupied incessantly with the consideration of the 
limits prescribed to their power by nature, they became 
so entirely convinced that nothing was at their disposal 
except their own thoughts, that this conviction was of 
itself sufficient to prevent their entertaining any desire 
of other objects; and over their thoughts they acquired 
a sway so absolute, that they had some ground on this 
account for esteeming themselves more rich and more 
powerful, more free and more happy, than other men 
who, whatever be the favours heaped on them by nature 
and fortune, if destitute of this philosophy, can never 
command the realisation of all their desires. 
cSin fine, to conclude this code of morals, 1 thought of 
reviewing the different occupations of men in this life, 
wath the view of making choice of the best. And, with- 
out wishing to offer any remarks on the employments of 
others, I may state that it was my conviction that I could 
not do better than continue in that in which I was 
engaged, viz., in devoting my whole life to the culture of 
my reason, and in making the greatest progress I was able 
in the knowledge of truth, on the principles of the method 
which I had prescribed to myself./This method, from 
the time I had begun to apply it, had been to me the 
source of satisfaction so intense as to lead me to believe 
that more perfect or more innocent could not be enjoyed 
in this life; and as by its means I daily discovered truths 
that appeared to me of some importance, and of which 
other men were generally ignorant, the gratification thence 
arising so occupied my mind that I was wholly indifferent 
to every other object. Besides, the three preceding 
maxims were founded singly on the design of continuing 
the work of self-instruction. For since God has endowed 
each of us with some light of reason by which to distin- 
guish truth from error, I could not have believed that I 
ought for a single moment to rest satisfied with the_ 
opinions of another, unless I had resolved to exercise my^ 

Discourse on Method 23 

own judgment in examining these whenever I should be 
duly qualified for the task. Nor could I have proceeded 
on such opinions without scruple, had I supposed that I 
should thereby forfeit any advantage for attaining still 
more accurate, should such exist. And, in fine, I could 
not have restrained my desires, nor remained satisfied, 
had I not followed a path in which I thought myself 
certain of attaining all the knowledge to the acquisition 
of which I was competent, as well as the largest amount 
of what is truly good which I could ever hope to secure. 
Inasmuch as we neither seek nor shun any object except 
in so far as our understanding represents it as good or 
bad, all that is necessary to right action is right judgment, 
and to the best action the most correct judgment, — that 
is, to the acquisition of all the virtues with all else that is 
truly valuable and within our reach; and the assurance 
of such an acquisition cannot fail to render us contented, 
•-^laving thus provided myself with these maxims, and 
Fiaving placed them in reserve along with the truths of 
faith, which have ever occupied the first place in my 
belief, I came to the conclusion that I might with freedom 
set about ridding myself of what remained of my opinions. 
And, inasmuch as I hoped to be better able successfully 
to accomplish this work by holding intercourse with 
mankind, than by remaining longer shut up in the retire- 
ment where these thoughts had occurred to me, I betook 
me again to travelling before the winter was well ended. 
And, during the nine subsequent years, I did nothing but 
roam from one place to another, desirous of being a 
spectator rather than an actor in the plays exhibited on 
the theatre of the world; and, as I made it my business 
in each matter to reflect particularly upon what might 
fairly be doubted and prove a source of error, I gradually 
rooted out from my mind all the errors which had hitherto 
crept into it. /Not that in this I imitated the sceptics 
who doubt only that they may doubt, and seek nothing 
beyond uncertainty itself; for, on the contrary, my design 
was singly to find ground of a-ssurance, and cast aside the 
loose earth and sand, that I might reach the rock or the 
clay. In this, as appears to me, I was successful enough; 
for, since I endeavoured to discover the falsehood or 

24 Discourse on Method 

incertitude of the propositions I examined, not by feeble 
conjectures, but by clear and certain reasonings, I met 
with nothing so doubtful as not to yield some conclusion 
of adequate certainty, although this were merely the 
inference, that the matter in question contained nothing 
certain. And, just as in pulling down an old house, 
we usually reserve the ruins to contribute towards the 
erection, so, in destroying such of my opinions as I 
judged to be ill-founded, I made a variety of observa- 
tions and acquired an amount of experience of which I 
availed myself in the establishment of more certain. 
And further, I continued to exercise myself in the method 
I had prescribed; for, besides taking care in general to 
conduct all my thoughts according to its rules, I reserved 
some hours from time to time which I expressly devoted 
to the employment of the method in the solution of 
mathematical difficulties, or even in the solution like- 
wise of some questions belonging to other sciences, but 
which, by my having detached them from such prin- 
ciples of these sciences as were of inadequate certainty, 
were rendered almost mathematical: the truth of this 
will be manifest from the numerous examples contained 
in this volume.^ And thus, without in appearance 
living otherwise than those who, with no other occupa- 
tion than that of spending their lives agreeably and 
innocently, study to sever pleasure from vice, and who, 
that they may enjoy their leisure without ennui, have 
recourse to such pursuits as are honourable, I was never- 
theless prosecuting my design, and making greater pro- 
gress in the knowledge of truth, than I might, perhaps, 
have made had I been engaged in the perusal of books 
merely, or in holding converse with men of letters. 

These nine years passed away, however, before I had 
come to any determinate judgment respecting the diffi- 
culties which form matter of dispute among the learned, 
or had commenced to seek the principles of any philo- 
sophy more certain than the vulgar. And the examples 
of many men of the highest genius, who had, in former 
times, engaged in this inquiry, but, as appeared to me, 

'IJ^^ u Si^^^^F^® °^ Method " was originally published along 
with the Dioptrics," the " Meteorics," and the *' Geometry."— Tr. 

Discourse on Method 25 

without success, led me to imagine it to be a work of so 
much difficulty, that I would not perhaps have ventured 
on it so soon had I not heard it currently rumoured that 
I had already completed the inquiry. I know not what 
were the grounds of this opinion; and, if my conversa- 
tion contributed in any measure to its rise, this must 
have happened rather from my having confessed my rQ^ 
ignorance with greater freedom than those are accus-" 
tomed to do who have studied a little, and expounded^ 
perhaps, the reasons that led me to doubt of many of 
those things that by others are esteemed certain, than 
from my having boasted of any system of philosophy. 
But, as I am of a disposition that makes me unwilling ten 
be esteemed different from what I really am, I thought it 
necessary to endeavour by all means to render myself 
worthy of the reputation accorded to me; and it is now 
exactly eight years since this desire constrained me to 
remove from all those places where interruption from any 
of my acquaintances was possible, and betake myself to 
this country,^ in which the long duration of the war has 
led to the establishment of such discipline, that the armies 
maintained seem to be of use only in enabling the in- 
habitants to enjoy more securely the blessings of peace; 
and where, in the midst of a great crowd actively engaged 
in business, and more careful of their own affairs than 
curious about those of others, I have been enabled to hve 
without being deprived of any of the conveniences to be 
had in the most populous cities, and yet as solitary and 
as retired as in the midst of the most remote deserts. 

^ Holland; to which country he withdrew in 1629. — 2"r. 


I AM in doubt as to the propriety of making my first 
meditations in the place above mentioned matter of dis- 
course; for these are so metaphysical, and so uncommon, 
as not, perhaps, to be acceptable to every one. And yet, 
that it may be determined whether the foundations that 
I have laid are sufficiently secure, I find myself in a 
measure constrained to advert to them/^I had long 
before remarked that, in relation to practice, it is some- 
times necessary to adopt, as if above doubt, opinions 
which we discern to be highly uncertain, as has been 
already said; but as I then desired to give my attention 
solely to the search after truth, I thought that a^Bio- 
cedure exactly the opp osite was called for, and tha t I 
" oUirht to relecc as aT3 soIu teIy^ false all opinions in rega r d 
4:o>^yfaich I could s uppose the lea st ground for doubt, in 
Of de l to usrert aifl whether a fte r thai Iheie iei ii ai ned^ 
aught in my beKeT tEat was whoITym3ubita ble7 Accord- 
iiigi57 icemg UiaL uui" senses sometimes decSve us, I was 
willing to suppose that there existed nothing really such 
as they presented to us; and because some men err in 
reasoning, and fall into paralogisms, even on the simplest 
matters of geometry, 1^ convinced that I was as open^ 
to error as any other,, rejected as false all the reasonings 
i had h ith e rto taken far demonstrations; and finally, 
when I considered that t4ie very same- t4ioughts (pre- 
Jej^aS 5ns)~whirh we oxpcriciiLC when awake -m ay^-ftlse- 
he experienced wh en wp arp a f ^l^^^P; m^HjI^ thpr^Jj^ nt tVnt „ 
tima-nAt- one of thom t.rno.j T r . nppnnpH tV i nt^ll thp nhjprtq 
>-(p]£sentatiQiis)~ that had ever cn ter^djnto my mind when 
awake.^Jmd^in them^e-more -truth-^haftH:^ iHus 
iny__dreajns^ But immediately upon this I observed 
that/whilst f thus wished to think that all was false, it 
was absolutely necessary that I, who thus thought, 
should be somewhat; and as I observed that this truth, 


Discourse on Method 27 

7 XhinM^Jisnc^^ so certain and of such evidence, 

lat no ground of doubt, however extravagant, could be 
alleged by the sceptics capable of shaking it, I concluded 
that I might, without scruple, accept it as the first prin- 
ciple of the philosophy of which I was in search. 

In the next place, I attentively examined what I was, 
and as I observed that I could suppose that I had 
no body, and that there was no world nor any place in 
which I might be ; but that I could not therefore suppose 
that I was not; and that, on the contrary, from the very 
circumstance that I thought to doubt of the truth of 
other things, it most clearly and certainly followed that 
I was; while, on the other hand, if I had only ceased to 
think, although all the other objects which I had ever 
imagined had been in reality existent, I would have had 
no reason to believe that I existed; I thence concluded 
that I was a substance whose whole essence or nature 
consists only in thinking, and which, that it may exist, 
has need of no place, nor is dependent on any material 
thing; so that "I,'' that is to say, the mind by which I 
am what I am, is wholly distinct from the body, and is 
even more easily known than the latter, and is such, that 
although the latter were not, it would still continue to be 
all that it is. 

After this I inquired in general into what is essential 
to the truth and certainty of a proposition; for since I 
had discovered one which I knew to be true, I thought 
that I must likewise be able to discover the ground of this 
certitude. And as I observed that in the words / think, 
hence I am, there is nothing at all which gives me assur- 
ance of their truth beyond this, that I see very clearly 
that in order to think it is necessary to exist,^I-Gaiidude^' 
thatXj»ight~take7-a^-ar-geneFa4-^:ule,4iie^ all 

_5ie,J±dQgfr-wh icli we v^ fy^^learly and distinctly conceive 
are true, only observing, however, thatt. there is some 
difficulty ^q^ri^htlydetermi!ite^^ we 


In the next place, from reflecting on the circumstance 
that I doubted, and that consequently my being was not 
wholly perfect (for I clearly saw that it was a greater 
perfection to know than to doubt), I was led to inquire 

28 Discourse on Method 

whence I had learned to think of something more perfect 
than myself; and I clearly recognised that I must hold 
this notion from some nature which in reality was more 
perfect. As for the thoughts of many other objects 
external to me, as of the sky, the earth, light, heat, and 
a thousand more, I was less at a loss to know whence 
these came; for since I remarked in them nothing which 
seemed to render them superior to myself, I could believe 
that, if these were true, they were dependencies ..on my 
^ own nature, in so far as it possessed a certain perfection, 
( and, if they were false, that, I held them from nothing, 
; that is to say, that they were in me because of a certain 
; imperfection of my nature. But this could not be the 
case with the idea of a nature more perfect than niyself ; 
for to receive it from nothing was a thing manifestly 
impossible; and, because it is not less repugnant that 
the more perfect should be an effect of, and dependence 
; on the less perfect, than that something should proceed 
I • from nothing, it was equally impossible that I could 
I hold it from myself: J accordingly, it but remained that 
^ it had been placed in me by a nature which was in reality 
more perfect than mine, and which even possessed 
within itself all the perfections of which I could form any 
|r. idea; that is to say, in a single woid, which was GodLJ 
!'^-.^|And to this I added that, since I knew some perfections 
which I did not possess, I was not the only being in exist- 
; ence)(I will here, with your permission, freely use the 
i tenris of the schools); but, on the contrary, that there 
I was of necessity some other more perfect Being upon 
I whom I was dependent, and from whom I had received 
I all that I possessed! ^^^ ^^ ^ ^^^ existed alone, and inde- 
j pendently of every other being,. so as to have had from 
I myself all the perfection, however little, which I actually 
possessed, I should have been able, for the same reason, 
to have had from myself the whole remainder of per- 
fection, of the want of which I was conscious, and thus 
could of myself have become infinite, eternal, immutable, 
I omniscient, all-powerful, and, in fine, have possessed all 
{ the perfections which I could recognise in GodA For in 
I order to know the nature of God (whose existence has 
/ been established by the preceding reasonings), as far as 

Discourse on Method 29 

my own nature permitted^ I had only to consider in 
refefence to all the properties of which I found in my 
mind some idea, whether their possession was a mark of 
perT ectiprTI ^nd I was assured that no one which indicated 
any "Imperfection was in hini7an3 tKat hone of the rest 
was awanting. XbiiS._I_.perceiyed._...^^^^ 
stancy^ sadness, and such like, could not be found in " 
God, since I myself would have been happy to be free 
from them. Besides, I had ideas of many sensible and 
corporeal things; for although I might suppose that I 
was dreaming, and that all which I saw or imagined was 
false, I could not, nevertheless, deny that the ideas were 
in reality in my thoughts. But, because I had already 
very clearly recognised in myself that the intelligent 
nature is distinct from the corporeal, and as I observed 
that all composition is an evidence of dependency, and 
that a state of dependency is manifestly a state of imper- 
fection, I therefore determined that it could not be a per- 
fection in God to be compounded of these two natures, 
and that consequently he was not so compounded; but 
that if tliere were any bodies in the world, or even any 
ijitelligences, or other natures that were not wholly 
perfect, their existence depended on his power in such a 
way that they could not subsist without him for a single 

I was disposed straightway to search for other truths; 
and when I had represented to myself the object of the 
geometers, which I conceived to be a continuous body, 
or a space indefinitely extended in length, breadth, and 
height or depth, divisible into divers parts which admit 
of different figures and sizes, and of being moved or trans- 
posed in all manner of ways (for all this the geometers 
suppose to be in the object they contemplate), I went 
over some of their simplest demonstrations. And, in the 
first place, I observed, that the great certitude which by 
common consent is accorded to these demonstrations, is 
founded solely upon this, that they are clearly conceived 
in accordance with the rules I have already laid down. 
In the next place, I perceived that there was nothing at 
all in these demonstrations which could assure me of the 
existence of their object: thus, for example, supposing a 

30 Discourse on Method 

triangle to be given, I distinctly perceived that its three 
angles were necessarily equal to two right angles, but I 
did not on that account perceive anything which could 
assure me that any triangle existed: while, on the con- 
trary, recurring to the examination of the idea of a 
Perfect Being, I found that the existence of the Being 
was comprised in the idea in the same way that the 
equality of its three angles to two right angles is com- 
prised in the idea of a triangle, or as in the idea of a 
sphere, the equidistance of all points on its surface from 
the centre, or even still more clearly; and that conse- 
quently it is at least as certain that God, who is this 
Perfect Being, is, or exists, as any demonstration of 
geometry can be. 

But the reason which leads many to persuade them- 
selves that there is a difficulty in knowing this truth, 
and even also in knowing what their mind really is, is 
that they never raise their thoughts above sensible 
objects, and are so accustomed to consider nothing 
except by way of imagination, which is a mode of thinking 
limited to material objects, that all that is not imaginable 
seems to them not intelligible. The truth of this is 
sufficiently manifest from the single circumstance, that 
the philosophers of the schools accent as a maxim that 
there is nothing in the understanding which was not 
previously in the senses, in which however it is certain 
that the ideas of God and of the soul hav^e never been; 
and it appears to me that they who make use of their 
imagination to comprehend these ideas do exactly the 
some thing as if, in order to hear sounds or smell odours, 
they strove to avail themselves of their eyes; unless 
indeed that there is this difference, that the sense of sight 
does not afford us an inferior assurance to those of smell 
or hearing; in place of which, neither our imagination 
nor our senses can give us assurance of anything unless 
our understanding intervene. 

Finally, if there be still persons who are not sufficiently 
persuaded of the existence of God and of the soul, by the 
reasons I have adduced, I am desirous that they should 
know that all the other propositions, of the truth of which 
they deem themselves perhaps more assured, as that we 

Discourse on Method 31 

have a body, and that there exist stars and an earth, and 
such like, are less certain; for, although we have a moral 
assurance of these things, which is so strong that there 
is an appearance of extravagance in doubting of their 
existence, yet at the same time no one, unless his intellect 
is impaired, can deny, when the question relates to a 
metaphysical certitude, that there is sufficient reason to 
exclude entire assurance, in the observation that when 
asleep we can in the same way imagine ourselves possessed 
of another body and that we see other stars and another 
earth, when there is nothing of the kind. For how do we 
know that the thoughts which occur in dreaming are 
false rather than those other which we experience when 
awake, since the former are often not less vivid and 
distinct than the latter ? And though men of the highest 
genius study this question as long as they please, I do 
not believe that they will be able to give any reason 
which can be sufficient to remove this doubt, unless they 
presuppose the existence of God. For, in the first place, 
even the principle which I have already taken as a rule, 
viz., that all the things which we clearly and distinctly 
conceive are true, is certain only because God is or exists, 
~and because he is a Perfect Being,.and because all that 
we possess is derived from him: whence it follows that 
our ideas or notions, which to the extent of their clearness 
and distinctness are real, and proceed from God, must 
to that extent be true. Accordingly, whereas we not 
unfrequently have ideas or notions in which some falsity 
is contained, this can only be the case with such as are 
to some extent confused and obscure, and in this proceed 
from nothing (participate of negation), that is, exist in 
us thus confused because we are not wholly perfect. And 
it is evident that it is not less repugnant that falsity or 
imperfection, in so far as it is imperfection, should proceed 
from God, than that truth or perfection should proceed 
from nothing. But if we did not know that ajl iiyhich 
>yc possess of real and true proceeds from a Perfect and 
Infinite Being, however clear and distinct our ideas 
might be, we should have no ground on that account 
for the assurance that they possessed the perfection of 
being true. 

32 Discourse on Method 

But after the knowledge of God and of the soul has 
rendered us certain of this rule, w£,£an easilY^nderstand 

7^ig^£nnivm THg^p fhtesTge grg^^^o ^ called m questio n 
olh^R^mTTyTof t he^jlusions o T"o^^ For ifit 

li^pened thataiTmSivH when asleep, had some 

very distinct idea, as, for example, if a geometer should 
discover some new demonstration, the circumstance of 
his being asleep would not militate against its truth; and 
as for the most ordinary error of our dreams, which 
consists in their representing to us various objects in the 
same way as our external senses, this is not prejudicial, 
since it leads us very properly to suspect the truth of the 
ideas of sense; for we are not unfrequently deceived in 
the same manner when awake; as when persons in the 
jaundice see all objects yellow, or when the stars or bodies 
at a great distance appear to us much smaller than they 
are. For, in fine, whether awake or asleep, we ought 
never to allow ourselves to be persuaded of the truth of 
anything unless on the evidence of pur reason. And it 
must be noted that I say of our reason, and not of our 
imagination or of our senses : thus, for example, although 
we very clearly see the sun, we ought not therefore to 
determine that it is only of the size which our sense of 
sight presents; and we may very distinctly imagine the 
head of a lion joined to the body of a goat, without being 
therefore shut up to the conclusion that a chimaera exists; 
for it is not a dictate of reason that what we thus see or 
imagine is in reality existent; but it plainly tells us that 
all our ideas or notions contain in them some truth; for 
otherwise it could not be that God, who is wholly perfect 
and veracious, should have placed them in us. And 
because our reasonings are never so clear or so complete 
during sleep as when we are awake, although sometimes 
the acts of our imagination are then as lively and distinct, 
if not more so than in our waking moments, reason 
further dictates that, since all our thoughts cannot be 
true because of our partial imperfection, those possessing 
truth must infallibly be found in the experience of our 
waking moments rather than in that of our dreams. 


I WOULD here willingly have proceeded to exhibit the 

whole chain of truths which I deduced from these primary; 

but as with a view to this it would have been necessary 

now to treat of many questions in dispute among the 

learned, with whom I do not wish to be embroiled, I 

believe that it will be better for me to refrain from this 

exposition, and only mention in general what these truths 

are, that the more judicious may be able to determine 

whether a more special account of them would conduce 

to the public advantage. I have ever remained firm 

in my original resolution to suppose no other principle 

than that of which I have recently availed myself in 

demonstrating the existence of God and of the soul, and 

to accept as true nothing that did not appear to me 

more clear and certain than the demonstrations of the 

geometers had formerly appeared; and yet I venture to 

state that not only have I found means to satisfy myself 

in a short time on all the principal difficulties which are 

usually treated of in philosophy, but I have also observed 

certain laws established in nature by God in such a 

manner, and of which he has impressed on our minds 

such notions, that after we have reflected sufficiently 

upon these, we cannot doubt that they are accurately 

observed in all that exists or takes place in the world: 

and farther, by considering the concatenation of these 

laws, it appears to me that I have discovered many truths 

more useful and more important than all I had before 

learned, or even had expected to learn. 

But because I have essayed to expound the chief of 
these discoveries in a treatise which certain considera- 
tions prevent me from publishing, I cannot make the 
results known more conveniently than by here giving 
a summary of the contents of this treatise. It was my 
design to comprise in it all that, before I set myself to 

33 c 

34 Discourse on Method 

write it, I thought I knew of the nature of material 
objects. But like the painters who, finding themselves 
unable to represent equally well on a plain surface all 
the different faces of a solid body, select one of the chief, 
on which alone they make the light fall, and throwing 
the rest into the shade, allow them to appear only in so 
far as they can be seen while looking at the principal 
one; so, fearing lest I should not be able to comprise in 
my discourse all that was in my mind, I resolved to ex- 
pound singly, though at considerable length, my opinions 
regarding light; then to take the opportunity of adding 
something on the sun and the fixed stars, since light 
almost wholly proceeds from them; on the heavens since 
they transmit it; on the planets, comets, and earth, since 
they reflect it; and particularly on all the bodies that are 
upon the earth, since they are either coloured, or trans- 
parent, or luminous; and finally on man, since he is the 
spectator of these objects. Further, to enable me to cast 
this variety of subjects somewhat into the shade, and to 
express my judgment regarding them with greater freedom, 
without being necessitated to adopt or refute the opinions 
of the learned, I resolved to leave all the people here to 
•their disputes, and to speak only of what would happen 
in a new world, if God were now to create somewhere in 
the imaginary spaces matter sufficient to compose one, 
and were to agitate variously and confusedly the different 
parts of this matter, so that there resulted a chaos as 
disordered as the poets ever feigned, and after that did 
nothing more than lend his ordinary concurrence to nature, 
and allow her to act in accordance with the laws which 
he had established. On this supposition, I, in the first 
place, described this matter, and essayed to represent it 
in such a manner that to my mind there can be nothing 
clearer and more intelligible, except what has been 
recently said regarding God and the soul; for I even 
expressly supposed that it possessed none of those forms 
or qualities which are so debated in the schools, nor in 
general anything the knowledge of which is not so natural 
to our minds that no one can so much as imagine himself 
ignorant of it. Besides, I have pointed out what are the 
laws of nature; and^ with no other principle upon which 

Discourse on Method 35 

tQ _found my reasonings exceptJ Lha infinite-fteriection- of 
God, I endeavoured tojdem^^^ 

there could^be any room for doubt, and to proye that 
the}7' are such, that even if God had created more worlds, 
there could have been none in which these laws were not 
obseryed. Thereafter, I showed how the greatest part 
of the matter of this chaos must, in accordance with these 
laws, dispose and arrange itself in such a way as to present 
the appearance of heavens; how in the meantime some 
of its parts must compose an earth and some planets and 
comets, and others a sun and fixed stars. And, making 
a digression at this stage on the subject of light, I ex- 
pounded at considerable length what the nature of that 
light must be which is found in the sun and the stars, and 
how thence in an instant of time it traverses the immense 
spaces of the heavens, and how from the planets and 
comets it is reflected towards the earth. To this I like- 
wise added much respecting the substance, the situation, 
the motions, and all the different qualities of these heavens 
and stars ; so that I thought I had said enough respecting 
them to show that there is nothing observable in the 
heavens or stars of our system that must not, or at least 
may not appear precisely alike in those of the system 
which I described. I came next to speak of the earth in 
particular, and to show how, even though I had expressly 
supposed that God had given no weight to the matter of 
which it is composed, this should not prevent all its parts 
from tending exactly to its centre; how with water and 
air on its surface, the disposition of the heavens and 
heavenly bodies, more especially of the moon, must cause 
a flow and ebb, like in all its circumstances to that observed 
in our seas, as also a certain current both of water and air 
from east to west, such as is likewise observed between 
the tropics; how the mountains, seas, fountains, and 
rivers might naturally be formed in it, and the metals 
produced in the mines, and the plants grow in the fields; 
and in general, how all the bodies which are commonly 
denominated mixed or composite might be generated: 
and, among other things in the discoveries alluded to, 
inasmuch as besides the stars, I knew nothing except fire 
which produces light, I spared no pains to set forth all 

36 Discourse on Method 

that pertains to its nature,— the manner of its production 
and support, and to explain how heat is sometimes 
found without light, and light without heat; to show 
how it can induce various colours upon different bodies 
and other diverse qualities; how it reduces some to a 
liquid state and hardens others; how it can consume 
almost all bodies, or convert them into ashes and smoke; 
and finally, how from these ashes, by the mere intensity 
of its action, it forms glass: for as this transmutation of 
ashes into glass appeared to me as wonderful as any 
other in nature, I took a special pleasure in describing it. 

I was not, however, disposed, from these circumstances, 
to conclude that this world had been created in the 
manner I described; for it is much more likely that God 
made it at the first such as it was to be. But this is 
certain, and an opinion commonly received among 
theologians, that the action by which he now sustains 
it is the same with that by which he originally created it; 
so that even although he had from the beginning given 
it no other form than that of chaos, provided only he had 
established certain laws of nature, and had lent it his 
concurrence to enable it to act as it is wont to do, it may 
be believed, without discredit to the miracle of creation, 
that, in this way alone, things purely material might, in 
course of time, have become such as we observe them at 
present; and their nature is much more easily conceived 
when they are beheld coming in this manner gradually 
into existence, than when they are only considerecl as 
produced at once in a finished and perfect state. 

From the description of inanimate bodies and plants, 
I passed to animals, and particularly to man. But 
since I had not as yet sufficient knowledge to enable me 
to treat of these in the same manner as of the rest, that 
is to say, by deducing effects from their causes, and by 
showing from what elements and in what manner nature 
must produce them, i remained satisfied with the sup- 
position that God formed the body of man wholly like 
to one of ours, as well in the external shape of the members 
as in the internal conformation of the organs, of the same 
matter with that I had described, and at first pkcedin it 
no rational soul, nor any other principle, in room of the 

Discourse on Method 37 

vegetative or sensitiv e soul, beyond kindling in the hear t 

one of thosFTrfes"~without light, such as I had already 
described, and which I thought was not different from 
the heat in hay that has been heaped together before it 
is dry, or that which causes fermentation in new wines 
before they are run clear of the fruit. For, when I 
examined the kind of functions which might, as conse- 
quences of this supposition, £xist in this body, I foun d 
precisely all t hose which may exist in us independently 
of all power^of thinking, and consequently without beijig 
in any measure owing to the soul ; in other words, to that 
part of us which is distinct from the body, and of which 
it has been said above that the nature distinctively 
consists in thinking, — functions in which the animals 
void of reason may be said wholly tolresemble us j T)iit 
"among which I could not discover any of those that, as 
dependent on thought alone, belong to us as men, while, 
on the other hand, I^did afterwards discover thesje.,.as 
\ soon as I supposed God to have created a rational soul, 
! and to have annexed it to this body in a particular 
manner which I described. 

But, in order to show how I there handled this matter, 
; I mean here to give the explication of the motion of the 
j heart and arteries, which, as the first and most general 
I motion observed in animals, will afford the means of 
readily determining what should be thought of all the 
rest. And that there may be less difficulty in understand- 
ing what I am about to say on this subject, I advise those 
who are not versed in anatomy, before they commence 
the perusal of these observations, to take the trouble of 
getting dissected in their presence the heart of some large 
animal possessed of lungs (for this is throughout suffi- 
ciently like the human), and to have shown to them its 
two ventricles or cavities: in the first place, that in the 
right side, with which correspond two very ample tubes, 
viz., the hollow vein (vena cava), which is the principal 
jj receptacle of the blood, and the trunk of the tree, as it 
were, of which all the other veins in the body are branches ; 
and the arterial vein (vena arteriosa), inappropriately so 
denominated, since it is in truth only an artery, which, 
taking its rise in the heart, is divided, after passing out 

^8 Discourse on Method 

from it, into many branches which presently disperse them- 
selves all over the lungs; in the second place, the cavity 
in the left side, with which correspond in the same manner 
two canals in size equal to or larger than the preceding, 
viz., the venous artery (artena venosa\ likewise inap- 
propriately thus designated, because it is siniply a vein 
which comes from the lungs, where it is divided into 
many branches, interlaced with those of the arterial vein, 
and those of the tube called the windpipe, through which 
the air we breathe enters; and the great artery which, 
issuing from the heart, sends its branches all over the 
body. I should wish also that such persons were care- 
fully shown the eleven pellicles which, like so many small 
valves, open and shut the four orifices that are in these 
two cavities, viz., three at the entrance of the hollow 
vein, where they are disposed in such a manner as by no 
means to prevent the blood which it contains from flow- 
ing into the right ventricle of the heart, and yet exactly 
to prevent its flowing out; three at the entrance to the 
arterial vein, which, arranged in a manner exactly the 
opposite of the former, readily permit the blood con- 
tained in this cavity to pass into the lungs, but hinder 
that contained in the lungs from returning to this cavity; 
and, in like manner, two others at the mouth of the 
venous artery, which allow the blood from the lungs to 
flow into the left cavity of the heart, but preclude its 
return; and three at the mouth of the great artery, 
which suffer the blood to flow from the heart, but prevent 
its reflux. Nor do we need to seek any other reason for 
the number of these pellicles beyond this that the orifice 
of the venous artery being of an oval shape from the 
nature of its situation, can be adequately closed with 
two, whereas the others being round are more con- 
veniently closed with three. Besides, I wish such 
persons to observe that the grand artery and the arterial 
vein are of much harder and firmer texture than the 
venous artery and the hollow vein; and that the two 
last expand before entering the heart, and there form, 
as it were, two pouches denominated the auricles of the 
heart, which are composed of a substance similar to that 
of the heart itself; and that there is always more warmth 

Discourse on Method 39 

in the heart than in any other part of the body; and, 
finally, that this heat is capable of causing any drop of 
blood that passes into the cavities rapidly to expand and 
dilate, just as all liquors do when allowed to fall drop by 
drop into a highly heated vessel. 

For, after these things, it is not necessary for me to say 
anything more with a view to explain the motion of the 
heart, except that when its cavities are not full of blood, 
into these the blood of necessity flows, — from the hollow 
vein into the right, and from the venous artery into the 
left; because these two vessels are always full of blood, 
and their orifices, which are turned towards the heart, 
cannot then be closed. But as soon as two drops of 
blood have thus passed, one into each of the cavities, 
these drops which cannot but be very large, because the 
orifices through which they pass are wide, and the vessels 
from which they come full of blood, are immediately 
rarefied, and dilated by the heat they meet with. In 
this way they cause the whole heart to expand, and at 
the same time press home and shut the five small valves 
that are at the entrances of the two vessels from which 
they flow, and thus prevent any more blood from coming 
down into the heart, and becoming more and more 
rarefied, they push open the six small valves that are in 
the orifices of the other two vessels, through which they 
pass out, causing in this way all the branches of the 
arterial vein and of the grand artery to expand almost 
simultaneously with the heart — which immediately there- 
after begins to contract, as do also the arteries, because 
the blood that has entered them has cooled, and the six 
small valves close, and the five of the hollow vein and of 
the venous artery open anew and allow a passage to other 
two drops of blood, which cause the heart and the arteries 
again to expand as before. And, because the blood 
which thus enters into the heart passes through these 
two pouches called auricles, it thence happens that their 
motion is the contrary of that of the heart, and that 
when it expands they contract. But lest those who are 
ignorant of the force of mathematical demonstrations, 
and who are not accustomed to distinguish true reasons 
from mere verisimilitudes, should venture, without ex- 

40 Discourse on Method 

amination, to deny what has been said, I wish it to be 
considered that the motion which I have now explained 
follows as necessarily from the very arrangement of the 
parts, which may be observed in the heart by the eye 
alone, and from the heat which may be felt with the 
fingers, and from the nature of the blood as learned from 
experience, as does the motion of a clock from the power, 
the situation, and shape of its counterweights and wheels. 
~~^ But if it be asked how it happens that the blood in the 
veins, flowing in this way continually into the heart, is 
not exhausted, and why the arteries do not become too 
full, since all the blood which passes through the heart 
flows into them, I need only mention in reply what has 
been written by a physician ^ of England, who has the 
honour of having broken the ice on this subject, and of 
having been the first to teach that there are many small 
passages at the extremities of the arteries, through which 
the blood received by them from the heart passes into 
the small branches of the veins, whence it again returns 
to the heart; so that its course amounts precisely to a 
perpetual circulation. Of this we have abundant proof 
in the ordinary experience of surgeons, who, by binding 
the arm with a tie of moderate straitness above the part 
where they open the vein, cause the blood to flow more 
copiously than it would have done without any ligature; 
whereas quite the contrary would happen were they to 
bind it below; that is, between the hand and the opening, 
or were to make the ligature above the opening very 
tight. For it is manifest that the tie, moderately 
straitened, while adequate to hinder the blood already 
in the arm from returning towards the heart by the 
veins, cannot on that account prevent new blood from 
coming forward through the arteries, because these are 
situated below the veins, and their coverings, from their 
greater consistency, are more difficult to compress; and 
also that the blood which comes from the heart tends 
to pass through them to the hand with greater force than 
it does to return from the hand to the heart through the 
veins. And since the latter current escapes from the 
arm by the opening made in one of the veins, there must 
^Harvey— La/. Tr. 

Discourse on Method 41 

of necessity be certain passages below the ligature, that 
is, towards the extremities of the arm through which it 
can come thither from the arteries. This physician 
likewise abundantly establishes what he has advanced 
respecting the motion of the blood, from the existence 
of certain pellicles, so disposed in various places along 
the course of the veins, in the manner of small valves, as 
not to permit the blood to pass from the middle of the 
body towards the extremities, but only to return from 
the extremities to the heart; and farther, from experi- 
ence which shows that all the blood which is in the body 
may flow out of it in a very short time through a single 
artery that has been cut, even although this had been 
closely tied in the immediate neighbourhood of the heart, 
and cut between the heart and the ligature, so as to 
prevent the supposition that the blood flowing out of it 
could come from any other quarter than the heart. 

But there are many other circumstances which evince 
that what I have alleged is the true cause of the motion 
of the blood: thus, in the first place, the difference that 
is observed between the blood which flows from the 
veins, and that from the arteries, can only arise from this, 
that being rarefied, and, as it were, distilled by passing 
through the heart, it is thinner, and more vivid, and 
warmer immediately after leaving the heart, in other 
words, when in the arteries, than it was a short time 
before passing into either, in other words, when it was in 
the veins ; and if attention be given, it will be found that 
this difference is very marked only in the neighbour- 
hood of the heart; and is not so evident in parts more 
remote from it. In the next place, the consistency of the 
coats of which the arterial vein and the great artery are 
composed, sufficiently shows that the blood is impelled 
against them with more force than against the veins. 
And why should the left cavity of the heart and the 
great artery be wider and larger than the right cavity 
and the arterial vein, were it not that the blood of the 
venous artery, having only been in the lungs after it has 
passed through the heart, is thinner, and rarefies more 
readily, and in a higher degree, than the blood which 
proceeds immediately from the hollow vein? And what 

42 Discourse on Method 

can physicians conjecture from feeling the pulse unless 
they know that according as the blood changes its nature 
it can be rarefied by the warmth of the heart, in a higher 
or lower degree, and more or less quickly than before? 
And if it be inquired how this heat is communicated to 
the other members, must it not be admitted that this is 
effected by means of the blood, which, passing through 
the heart, is there heated anew, and thence diffused over 
all the body? Whence it happens, that if the blood be 
withdrawn from any part, the heat is likewise withdrawn 
by the same means; and although the heart were as hot 
as glowing iron, it would not be capable of warming the 
feet and hands as at present, unless it continually sent 
thither new blood. We likewise perceive from this, that 
the true use of respiration is to bring sufficient fresh air 
into the lungs, to cause the blood which flows into them 
from the right ventricle of the heart, where it has been 
rarefied and, as it were, changed into vapours, to become 
thick, and to convert it anew into blood, before it flows 
into the left cavity, without which process it would be 
unfit for the nourishment of the fire that is there. This 
receives confirmation from the circumstance, that it is 
observed of animals destitute of lungs that they have 
also but one cavity in the he?,rt, and that in children 
who cannot use them while in the womb, there is a hole 
through which the blood flows from the hollow vein into 
the left cavity of the heart, and a tube through which it 
passes from the arterial vein into the grand artery with- 
out passing through the lung. In the next place, how 
could digestion be carried on in the stomach unless the 
heart communicated heat to it through the arteries, and 
along with this certain of the more fluid parts of the blood, 
which assist in the dissolution of the food that has been 
taken in? Is not also the operation which converts the 
juice of food into blood easily comprehended, when it is 
considered that it is distilled by passing and repassing 
through the heart perhaps more than one or two hundred 
times in a day? And what more need be adduced to 
explain nutrition, and the production of the different 
humours of the body, beyond saying, that the force with 
which the blood, in being rarefied, passes from the heart 

Discourse on Method 43 

towards the extremities of the arteries^ causes certain of 
its parts to remain in the members at which they arrive, 
and there occupy the place of some others expelled by 
them; and that according to the situation, shape, or 
smallness of the pores with which they meet, some rather 
than others flow into certain parts, in the same way that 
some sieves are observed to act, which, by being variously 
perforated, serve to separate different species of grain? 
And, in the last place, what above all is here worthy 
of observation, is the generation of the animal spirits, 
which are like a very subtle wind, or rather a very pure 
and vivid flame which, continually ascending in great 
abundance from the heart to the brain, thence pene- 
trates through the nerves into the muscles, and gives 
motion to all the members; so that to account for other 
parts of the blood which, as most agitated and penetrat- 
ing, are the fittest to compose these spirits, proceeding 
towards the brain, it is not necessary to suppose any 
other cause, than simply, that the arteries which carry 
them thither proceed from the heart in the most direct 
lines, and that, according to the rules of mechanics, 
which are the same with those of nature, when many 
objects tend at once to the same point where there is not 
sufficient room for all (as is the case with the parts of 
the blood which flow forth from the left cavity of the 
heart and tend towards the brain), the weaker and less 
agitated parts must necessarily be driven aside from that 
point by the stronger which alone in this way reach it. 

I had expounded all these matters with sufficient 
minuteness in the treatise which I formerly thought of 
publishing. And after these, I had shown what must 
be the fabric of the nerves and muscles of the human 
body to give the animal spirits contained in it the power 
to move the members, as when we see heads shortly 
after they have been struck off still move and bite the 
earth, although no longer animated; what changes 
must take place in the brain to produce waking, sleep, 
and dreams; how light, sounds, odours, tastes, heat, 
and all the other qualities of external objects impress it 
with different ideas by means of the senses; how hunger, 
thirst, and the other internal affections can likewise 

44 Discourse on Method 

impress upon it divers ideas; what must be understood 
by the common sense {sensus communis) in which these 
ideas are received, by the memory which retains them, 
by the fantasy which can change them in various ways, 
and out of them compose new ideas, and which, by the 
same means, distributing the animal spirits through the 
muscles, can cause the members of such a body to move 
in as many different ways, and in a manner as suited, 
whether to the objects that are presented to its senses 
or to its internal affections, as can take place in our own 
case apart from the guidance of the will. Nor will this 
appear at all strange to those who are acquainted with 
the variety of movements performed by the different 
automata, or moving machines fabricated by human 
industry, and that with help of but few pieces compared 
with the great multitude of bones, muscles, nerves, 
arteries, veins, and other parts that are found in the 
body of each animal. Such persons will look upon this 
body as a machine made by the hands of God, which is in- 
comparably better arranged, and adequate to movements 
more admirable than is any machine of human invention. 
And here I specially stayed to show that, were there such 
machines exactly resembling in organs and outward form an 
ape or any other irrational animal, we could have no means 
of knowing that they were in any respect of a different 
nature from these animals; but if there were machines 
bearing the image of our bodies, and capable of imitating 
our actions as far as it is morally possible, there would 
still remain two most certain tests whereby to know that 
they were not therefore really men. Of these the first 
is that they could never use words or other signs arranged 
in such a manner as is competent to us in order to declare 
our thoughts to others: for we may easily conceive a 
machine to be so constructed that it emits vocables, and 
even that it emits some correspondent to the action 
upon it of external objects which cause a change in its 
organs; for example, if touched in a particular place it 
may demand what we wish to say to it; if in another 
it may cry out that it is hurt, and such like; but not 
that it should arrange them variously so as appositely to 
reply to what is said in its presence, as men of the lowest 

Discourse on Method 45 

grade of intellect can do. The second test is, that 
although such machines might execute many things 
with equal or perhaps greater perfection than any of 
us, they would, without doubt, fail in certain others 
from which it could be discovered that they did not act 
from knowledge, but solely from the disposition of their- 
organs: for while reason is an universal instrument 
that is alike available on every occasion, these organs, 
on the contrary, need a particular arrangement for each 
particular action; whence it must be morally impos- 
sible that there should exist in any machine a diversity 
of organs sufficient to enable it to act in all the occur- 
rences of life, in the way in which our reason enables 
us to act. Again, by means of these two tests we may 
likewise know the difference between men and brutes. 
For it is highly deserving of remark, that there are no 
men so dull and stupid, not even idiots, as to be incap- 
able of joining together different words, and thereby 
constructing a declaration by which to make their 
thoughts understood; and that on the other hand, there 
is no other animal, however perfect or happily circum- 
stanced, which can do the like. Nor does this inability 
arise from want of organs: for we observe that magpies 
and parrots can utter words like ourselves, and are yet 
unable to speak as we do, that is, so as to show that they 
understand what they say; in place of which men born 
deaf and dumb, and thus not less, but rather more than 
the brutes, destitute of the organs which others use in 
speaking, are in the habit of spontaneously inventing 
certain signs by which they discover their thoughts to 
those who, being usually in their company, have leisure 
to learn their language. And this proves not only that 
the brutes have less reason than man, but that they have 
none at all: for we see that very little is required to 
enable a person to speak; and since a certain inequality 
of capacity is observable among animals of the same 
species, as well as among men, and since some are more 
capable of being instructed than others, it is incredible 
that the most perfect ape or parrot of its species, should 
not in this be equal to the most stupid infant of its kind, 
or at least to one that was crack-brained, unless the soul 

46 Discourse on Method 

of brutes were of a nature wholly different from ours. 
And we ought not to confound speech with the natural 
movements which indicate the passions, and can be 
imitated by machines as well as manifested by animals; 
nor must it be thought with certain of the ancients, that 
the brutes speak, although we do not understand their 
language. For if such were the case, since they are 
endowed with many organs analogous to ours, they could 
as easily communicate their thoughts to us as to their 
fellows. It is also very worthy of remark, that, though 
there are many animals which manifest more industry 
than we in certain of their actions, the same animals are 
yet observed to show none at all in many others : so that 
the circumstance that they do better than we does not 
prove that they are endowed with mind, for it would 
thence follow that they possessed greater reason than 
any of us, and could surpass us in all things; on the 
contrary, it rather proves that they are destitute of 
reason, and that it is nature which acts in them accord- 
ing to the disposition of their organs: thus it is seen, 
that a clock composed only of wheels and weights can 
number the hours and measure time more exactly than 
we with all our skill. 

I had after this described the reasonable soul, and 
shown that it could by no means be educed from the 
power of matter, as the other things of which I had 
spoken, but that it must be expressly created; and that 
it is not sufficient that it be lodged in the human body 
exactly like a pilot in a ship, unless perhaps to move its 
members, but that it is necessary for it to be joined and 
united more closely to the body, in order to have sensa- 
tions and appetites similar to ours, and thus constitute 
a real man. I here entered, in conclusion, upon the 
subject of the soul at considerable length, because it is 
of the greatest moment: for after the error of those who 
deny the existence of God, an error which I think I 
have already sufficiently refuted, there is none that is 
more powerful in leading feeble minds astray from the 
straight path of virtue than the supposition that the 
\ soul of the brutes is of the same nature with our own; 
.and consequently that after this life we have nothing to 

Discourse on Method 47 

hope for or fear, more than flies and ants; in place of 
which, when we know how far they differ we much 
better comprehend the reasons which establish that the 
soul is of a nature wholly independent of the body, and 
that consequently it is not liable to die with the latter; 
and, finally, because no other causes are observed 
capable of destroying it, we are naturally led thence to 
judge that it is immortal. 


Three years have now elapsed since I finished the 
treatise containing all these matters; and I was begin- 
ning to revise it^ with the view to put it into the hands 
of a printer^ when I learned that persons to whom I 
greatly defer, and whose authority over my actions is 
hardly less influential than is my own reason over my 
thoughts, had condemned a certain doctrine in physics, 
published a short time previously by another individual,^ 
to which I will not say that I adhered, but only that, 
previously to their censure, I had observed in it nothing 
which I could imagine to be prejudicial either to religion 
or to the state, and nothing therefore which would have 
prevented me from giving expression to it in writing, if 
reason had persuaded me of its truth; and this led me 
to fear lest among my own doctrines likewise some one 
might be found in which I had departed from the truth, 
notwithstanding the great Cctre I have always taken not 
to accord belief to new opinions of which I had not the 
most certain demonstrations, and not to give expression 
to aught that might tend to the hurt of any one. This 
has been sufficient to make me alter my purpose of 
pubhshing them; for although the reasons by which I 
had been induced to take this resolution were very strong, 
yet my inclination, which has always been hostile to 
writing books, enabled me immediately to discover 
other considerations sufficient to excuse me for not under- 
taking the task. And these reasons, on one side and 
the other, are such, that not only is it in some measure 
my interest here to state them, but that of the public, 
perhaps, to know them. 

I have never made much account of what has pro- 
ceeded from my own mind; and so long as I gathered 
no other advantage from the method I employ beyond 

» Galileo.— Tf. 

Discourse on Method 49 

satisfying myself on some difficulties belonging to the 
speculative sciences, or endeavouring to regulate my 
actions according to the principles it taught me, I never 
thought myself bound to publish anything respecting 
it. For in what regards manners, every one is so full ^ 
of his own wisdom, that there might be found as many 
reformers as heads, if any were allowed to take upon 
themselves the task of mending them, except those whom 
God has constituted the supreme rulers of his people, 
or to whom he has given sufficient grace and zeal to be 
prophets ; and although my speculations greatly pleased 
myself, I believed that others had theirs, which perhaps 
pleased them still more. But as soon as I had acquired 
some general notions respecting physics, and beginning 
to make trial of them in various particular difficulties, 
had observed how far they can carry us, and how much 
they differ from the principles that have been employed 
up to the present time, I believed that I could not keep 
them concealed without sinning grievously against the ^ 
law by which we are bound to promote, as far as in us lies, / 
the general good of mankind. For by them I perceived 
it to be possible to arrive at knowledge highly useful in 
life; and in room of the speculative philosophy usually 
taught in the schools, to discover a practical, by means 
of which, knowing the force and action of fire, water, air, 
the stars, the heavens, and all the other bodies that sur- 
round us, as distinctly as we know the various crafts of 
our artisans, we might also apply them in the same way 
to all the uses to which they are adapted, and thus 
render ourselves the lords and possessors of nature. 
And this is a result to be desired, not only in order to the 
invention of an infinity of arts, by which we might be 
enabled to enjoy without any trouble the fruits of the 
earth, and all its comforts, but also and especially Jgr 
the preservation of health, which is without doubt, of 
all the blessings of this life, the first and fundamental 
one; for the mind is so intimately dependent upon the 
condition and relation of the organs of the body, that 
if any means can ever be found to render men wiser and 
more ingenious than hitherto, I believe that it is in 
medicine they must be sought for. It is true that the 



ro Discourse on Method 

science of medicine, as it now exists, contains few things 
whose utiHty is very remarkable: but without any wish 
to depreciate it, I am confident that there is no one, 
even among those whose profession it is, who does not 
admit that all at present known in it is almost nothing 
in comparison of what remains to be discovered; and 
that we could free ourselves from an infinity of maladies 
of body as well as of mind, and perhaps also even from 
the debility of age, if we had sufficiently ample know- 
ledge of their causes, and of all the remedies provided 
for us by nature. But since I designed to employ my 
whole life in the search after so necessary a science, and 
since I had fallen in with a path which seems to me such, 
that if any one follow it he must inevitably reach the end 
desired, unless he be hindered either by the shortness of 
life or the want of experiments, I judged that there could 
be no more effectual provision against these two im- 
pediments than if I were faithfully to communicate to 
the public all the little I might myself have found, and 
incite men of superior genius to strive to proceed farther, 
by contributing, each according to his inclination and 
ability, to the experiments which it would be necessary 
to make, and also by informing the public of all they jj 
might discover, so that, by the last beginning _where 
those before them had left off, and thus connecting^ the 
lives and labours of man}^, we might collectively proceed 
much farther than each by himself could do. 

I remarked, moreover, with respect to experiments, 
that they become always more necessary the more one 
is advanced in knowledge; for, at the commencement, 
it is better to make use only of what is spontaneously 
presented to our senses, and of which we cannot remain 
ignorant, provided we bestow on it any reflection, how- 
ever slight, than to concern ourselves about more un- 
common and recondite phenomena: the reason of which 
is, that the more uncommon often only mislead us so 
long as the causes of the more ordinary are still unknown; 
and the circumstances upon which they depend are 
almost always so special and minute as to be highly 
difficult to detect. But in this I have adopted the 
following order: first, I have essayed to find in general 

Discourse on Method 51 

the principles^j^r^fLrsLcauses of all_that is or can be in 
the world, without taking mto "consideration for this 
end anything but God himself who has created it, and 
without educing them from any other source than from 
certain germs of truths naturally existing in our minds. 
In the second place, I examined what were the first and 
most ordinary effects that_cpuld be dediici^ -fr^ 
causes; and it appears to me that, in this way, I have 
found heavens, stars, an earth, and even on the earth, 
water, air, fire, minerals, and some other things of this 
kind, which of all others are the most common and 
simple, and hence the easiest to know. Afterwards, 
when I wished to des(::end to the more particular, so 
many diverse objects presented themselves to me, that 
I believed it to be impossible for the human mind to 
distinguish the forms or species of bodies that are upon 
the earth, from an infinity of others which might have 
been, if it had pleased God to place them there, or conse- 
quently to apply them to our use, unless we rise to causes 
through their effects, and avail ourselves of many parti- 
cular experiments. Thereupon, turning over in my mind 
all the objects that had ever been presented to my senses, 
I freely venture to state that I have never observed any 
which I could not satisfactorily explain by the principles 
I had discovered. But it is necessary also to confess 
that the power of nature is so ample and vast, and these 
principles so simple and general, that I have hardly 
observed a single particular effect which I cannot at once 
recognise as capable of being deduced in many different 
modes from the principles, and that my greatest diffi- 
culty usually is to discover in which of these modes the 
effect is dependent upon them; for out of this difficulty 
I cannot otherwise extricate myself than by again seek- 
ing certain experiments, which may be such that their 
result is not the same, if it is in the one of these modes 
that we must explain it, as it would be if it were to be 
explained in the other. As to what remains, I am now 
in a position to discern, as I think, with sufficient clear- 
ness what course must be taken to make the majority 
of those experiments which may conduce tp.. this end : 
but I perceive likewise that they are such and so 

r2 Discourse on Method 

numerous, that neither my hands nor my income, though 
it were a thousand times larger than it is, would be suffi- 
cient for them all; so that, according as henceforward I 
shall have the means of making more or fewer experi- 
ments, I shall in the same proportion make greater or 
less progress in the knowledge of nature. This was what I 
had hoped to make known by the treatise I had written, 
and so clearly to exhibit the advantage that would thence 
accrue to the public, as to induce all who have the common 
good of man at heart, that is, all who are virtuous in 
truth, and not merely in appearance, or according to 
opinion, as well to communicate to me the experiments 
they had already made, as to assist me in those that 
remain to be made. 

But since that time other reasons have occurred to 
me, by which I have been led to change my opinion, and 
to think that I ought indeed to go on committing to 
writing all the results which I deemed of any moment, 
as soon as I should have tested their truth, and to bestow 
the same care upon them as I would have done had it 
been my design to publish them. This course com- 
mended itself to me, as well because I thus afforded 
myself more ample inducement to examine them 
thoroughly, for doubtless that is always more narrowly 
scrutinised which we believe will be read by many, than 
that which is written merely for our private use (and 
/ frequently what has seemed to me true when I first 
\ conceived it, has appeared false when I have set about 
\committing it to writing), as because I thus lost no oppor- 
tunity of advancing the interests of the public, as far as in 
me lay, and since thus likewise, if my writings possess any 
value, those into whose hands they may fall after my 
death may be able to put them to what use they deem 
proper. But I resolved by no means to consent to their 
publication during my hfetime, lest either the oppositions 
or the controversies to which they might give rise, or 
even the reputation, such as it might be, which they 
would acquire for me, should be any occasion of my losing 
the time that I had set apart for my own improvement. For 
though it be true that every one is bound to promote to 
the extent of his ability the good of others, and that to be 

Discourse on Method 53 

useful to no one is really to be worthless, yet it is likewise 
true that our cares ought to extend beyond the present; 
and it is good to omit doing what might perhaps bring 
some profit to the living, when we have in view the accom- 
plishment of other ends that will be of much greater 
advantage to posterity. And in truth, I am quite willing 
It should be known that the little I have hitherto learned 
is almost nothing in comparison with that of which I am 
ignorant, and to the knowledge of which I do not despair 
of being able to attain; for it is much the same with those 
who gradually discover truth in the sciences, as with 
those who when growing rich find less difficulty in making 
great acquisitions, than they formerly experienced when 
poor in making acquisitions of much smaller amount. 
Or they may be compared to the commanders of armies, 
whose forces usually increase in proportion to their 
victories, and who need greater prudence to keep together 
the residue of their troops after a defeat than after a 
victory to take towns and provinces. For he truly 
engages in battle who endeavours to surmount all the 
difficulties and errors which prevent him from reaching 
the knowledge of truth, and he is overcome in fight who 
admits a false opinion touching a matter of any generality 
and importance, and he requires thereafter much more 
skill to recover his former position than to make great 
advances when once in possession of thoroughly ascer- 
tained principles. As for myself, if I have succeeded in 
discovering any truths in the sciences (and I trust that 
what is contained in this volume ^ will show that I have 
found some), I can declare that they are but the conse- 
quences and results of five or six principal difficulties 
which I have surmounted, and my encounters with which 
I reckoned as battles in which victory declared for me. 
I will not hesitate even to avow my belief that nothing 
further is wanting to enable me fully to realise my designs 
than to gain two or three similar victories; and that I 
am not so far advanced in years but that, according to 
the ordinary course of nature, I may still have sufficient 
leisure for this end. But I conceive myself the more 
bound to husband the time that remains the greater my 

^ See p. 24. 

r^ Discourse on Method 

expectation of being able to employ it aright, and I should 
doubtless have much to rob me of it, were I to publish 
the principles of my physics: for although they are 
almost all so evident that to assent to them no more is 
needed than simply to understand them, and although 
there is not one of them of which I do not expect to be 
able to give demonstration, yet, as it is impossible that 
they can be in accordance with all the diverse opinions 
of others, I foresee that I should frequently be turned 
aside from my grand design, on occasion of the opposi- 
tion which they would be sure to awaken. 
It may be said, that these oppositions would be useful 
' both in making me aware of my errors, and, if my 
speculations contain anything of value, in bringing 
others to a fuller understanding of it; and still farther, 
as many can see better than one, in leading others who 

, are now beginning to avail themselves of my principles, 

\to assist me in turn with their discoveries. But though 
'% recognise my extreme liability to error, and scarce ever 
trust to the first thoughts which occur to me, yet the 
experience I have had of possible objections to my views 
prevents me from anticipating any profit from them. 
For I have already had frequent proof of the judgments, 
as well of those I esteemed friends, as of some others to 
whom I thought I was an object of indifference, and 
even of some whose malignity and envy would, I knew, 
determine them to endeavour to discover what partiality 
concealed from the eyes of my friends. But it has 
rarely happened that anything has been objected to me 
which I had myself altogether overlooked, unless it 
were something far removed from the subject: so that 
I have never met with a single critic of my opinions who 
did not appear to me either less rigorous or less equitable 
than myself. And further, I have never observed that 
any truth before unknown has been brought to light by 
the disputations that are practised in the schools; for 

^while each strives for the victory, each is much more 
/ occupied in making the best of mere verisimilitude, than 

\in weighing the reasons on both sides of the question; 
and those who have been long good advocates are not 
afterwards on that account the better judges. 

Discourse on Method 55 

As for the advantage that others would derive from 
the communication of my thoughts, it could not be 
very great; because I have not yet so far prosecuted 
them as that much does not remain to be added before 
they can be applied to practice. And I think I may 
say without vanity, that if there is any one who can 
carry them out that length, it must be myself rather 
than another: not that there may not be in the world 
many minds incomparably superior to mine, but because 
one cannot so well seize a thing and make it one's own, 
when it has been learned from anoth er, as^ when on ejias 
himself discovered it. And so true is this of the present 
subject that, though I have often explained some of my 
opinions to persons of much acuteness, who, whilst I was 
speaking, appeared to understand them very distinctly, 
yet, when they repeated them, I have observed that they 
almost always changed them to such an extent that I 
could no longer acknowledge them as mine. I am glad, 
by the way, to take this opportunity of requesting 
posterity never to believe on hearsay that anything has 
proceeded from me which has not been published by 
myself; and I am not at all astonished at the extrava- 
gances attributed to those ancient philosophers whose 
own writings we do not possess ; whose thoughts, however, 
I do not on that account suppose to have been really 
absurd, seeing they were among the ablest men of their 
times, but only that these have been falsely represented 
to us. It is observable, accordingly, that scarcelyTiTa 
sTngre^ instance has any one of their disciples surpassed 
them; and I am quite sure that the most devoted of the 
present followers of Aristotle would think themselves 
happy if they had as much knowledge of nature as he 
possessed, were it even under the condition that they 
should never afterwards attain to higher. In this respect 
they are like the ivy which never strives to rise a.b^^ 
tree that sustains it, and which frequently even returns 
downwards when it has reached the top; for it seems 
to me that they also sink, in other words, render them- 
selves less wise than they would be if they gave up study, 
who, not contented with knowing all that is intelligibly 
explained in their author, desire in addition to find in 

56 Discourse on Method 

him the solution of many difficulties of which he says not 
a word, and never perhaps so much as thought. Their 
fashion of philosophising, however, is well suited to 
persons whose abilities fall below mediocrity; for the 
obscurity of the distinctions and principles of which they 
make use enables them to speak of all things with as 
much confidence as if they really knew them, and to 
defend all that they say on any subject against the most 
subtle and skilful, without its being possible for any one 
to convict them of error. In this they seem to me to be 
like a blind man, who, in order to fight on equal terms 
with a person that sees, should have made him descend 
to the bottom of an intensely dark cave : and I may say 
that such persons have an interest in my refraining from 
publishing the principles of the philosophy of which I 
make use; for, since these are of a kind the simplest and 
most evident, I should, by publishing them, do much the 
same as if I were to throw open the windows, and allow 
the light of day to enter the cave into which the com- 
batants had descended. But even superior men have 
no reason for any great anxiety to know these principles, 
for if what they desire is to be able to speak of all things, 
and to acquire a reputation for learning, they will gain 
their end more easily by remaining satisfied with the 
appearance of truth, which can be found without much 
difficulty in all sorts of matters, than by seeking the truth 
itself which unfolds itself but slowly and that only in 
some departments, while it obliges us, when we have to 
speak of others, freely to confess our ignorance. If, 
however, they prefer the knowledge of some few truths 
to the vanity of appearing ignorant of none, as such 
knowledge is undoubtedly much to be preferred, and, if 
they choose to follow a course similar to mine, they do 
not require for this that I should say anything more than 
I have already said in this discourse. For if they are 
capable of making greater advancement than I have 
niade, they will much more be able of themselves to 
discover all that I believe myself to have found; since 
as I have never examined aught except in order, it is 
certain that what yet remains to be discovered is in itself 
more difficult and recondite, than that which I have 

Discourse on Method ^y 

already been enabled to find, and the gratification would"" 
be much less in learning it from me than in discovering 
it for themseives. Besides this, the habit which they will .. 
acquire, by seeking first what is easy, and then passing 
onward slowly and step by step to the more difficult, will 
benefit them more than all my instructions. Thus^Tir^v 
my own case, I am persuaded that if I had been taught j 
from my youth all the truths of which I have since sought ' 
out demonstrations, and had thus learned them without 
labour, I should never, perhaps, have known any beyond Ji 
these; at least, I should never have acquired the habit 
and the facility which I think I possess in always dis- 
covering new truths in proportion as I give myself to the 
search. And, in a single word, if there is any work in the 
world which cannot be so well finished by another as by 
him who has commenced it, it is that at which I labour. 

It is true, indeed, as regards the experiments which may 
conduce to this end, that one man is not equal to the task 
of making them all ; but yet he can advantageously avail 
himself, in this work, of no hands besides his own, unless 
those of artisans, or parties of the same kind, whom he 
could pay, and whom the hope of gain (a means of great 
efficacy) might stimulate to accuracy in the performance 
of what was prescribed to them. For as to those who, 
through curiosity or a desire of learning, of their own 
accord, perhaps, offer him their services, besides that in 
general their promises exceed their performance, and that c 
they sketch out fine designs of which not one is ever 
realised, they will, without doubt, expect to be com- 
pensated for their trouble by the explication of some 
difficulties, or, at least, by compliments and useless 
speeches, in which he cannot spend any portion of his 
time without loss to himself. And as for the experiments 
that others have already made, even although these 
parties should be willing of themselves to communicate 
them to him (which is what those who esteem them 
secrets will never do), the experiments are, for the most 
part, accompanied with so many circumstances and 
superfluous elements, as to make it exceedingly difficult 
to disentangle the truth from its adjuncts; besides, he 
will find almost all of them so ill described, or even so 

r8 Discourse on Method 

/ false (because those who made them have v/ished to see 
in them only such facts as they deemed conformable to 
their principles), that, if in the entire number there should 
be some of a nature suited to his purpose, still their value 
could not compensate for the time what would be neces- 
sary to make the selection. So that if there existed any 
one whom we assuredly knew to be capable of making 
discoveries of the highest kind, and of the greatest possible 
utility to the public; and if all other men were therefore 
eager by all means to assist him in successfully prosecuting 
his designs, I do not see that they could do aught else for 
him beyond contributing to defray the expenses of the 
experiments that might be necessary; and for the rest, 
prevent his being deprived of his leisure by the unseason- 
able interruptions of any one. But besides that I neither 
have so high an opinion of myself as to be willing to make 
promise of anything extraordinary, nor feed on imagina- 
tions so vain as to fancy that the public must be much 
interested in my designs; I do not, on the other hand, 
own a soul so mean as to be capable of accepting from 
any one a favour of which it could be supposed that I 
was unworthy. 

These considerations taken together were the reason 
why, for the last three years, I have been unwilling to 
publish the treatise I had on hand, and why I even 
resolved to give publicity during my life to no other 
that was so general, or by which the principles of my 
physics might be understood. But since then, two other 
reasons have come into operation that have determined 
me here to subjoin some particular specimens, and give 
the public some account of my doings and designs. Of 
these considerations, the first is, that if I failed to do so, 
many who were cognisant of my previous intention to 
publish some writings, might have imagined that the 
reasons which induced me to refrain from so doing, were 
less to my credit than they really are; for although I am 
not immoderately desirous of glory, or even, if I may 
venture so to say, although I am averse from it in so far 
as I deem it hostile to repose which I hold in greater 
account than aught else, yet, at the same time, I have 
never sought to conceal my actions as if they were crimes. 

Discourse on Method 59 

nor made use of many precautions that I might remain 
unknown; and this partly because I should have thought 
such a course of conduct a wrong against myself, and 
partly because it would have occasioned me some sort of 
uneasiness which would again have been contrary to the 
perfect mental tranquillity which I court. And foras- 
much as, while thus indifferent to the thought alike of 
fame or of forgetfulness, I have yet been unable to 
prevent myself from acquiring some sort of reputation, 
I have thought it incumbent on me to do my best to save 
myself at least from being ill-spoken of. The other 
reason that has determined me to commit to writing these 
specimens of philosophy is, that I am becoming daily 
more and more alive to the delay which my design of 
self-instruction suffers, for want of the infinity of experj- 
ments I require, and which it is impossible for me to make 
without the assistance of others: and, without flattering 
myself so much as to expect the public to take a large 
share in my interests, I am yet unwilling to be found so 
far wanting in the duty I owe to myself, as to give occasion 
to those who shall survive me to make it matter of 
reproach against me some day, that I might have left 
them many things in a much more perfect state than I 
have done, had I not too much neglected to make them 
aware of the ways in which they could have promoted the 
accomplishment of my designs. 

And I thought that it was easy for me to select some 
matters which should neither be obnoxious to much 
controversy, nor should compel me to expound more 
of my principles than I desired, and which should yet 
be sufficient clearly to exhibit what I can or cannot 
accomplish in the sciences. Whether or not I have 
succeeded in this it is not for me to say; and I do not 
wish to forestall the judgments of others by speaking 
myself of my writings; but it will gratify me if they be 
examined, and, to afford the greater inducement to this, 
I request all who may have any objections to make to 
them, to take the trouble of forwarding these to my 
publisher, who will give me notice of them, that I may 
endeavour to subjoin at the same time my reply; and 
in this way readers seeing both at once will more easily 

6o Discourse on Method 

determine where the truth Hes; for I do not engage in 
any case to make prolix replies, but only with perfect 
frankness to avow my errors if I am convinced of them, 
or if I cannot perceive them, simply to state what I think 
is required for defence of the matters I have written, 
adding thereto no explication of any new matter that it 
may not be necessary to pass without end from one thing 
to another. 

If some of the matters of which I have spoken in the be- 
ginning of the "Dioptrics" and ''Meteorics'' should offend 
at first sight, because I call them hypotheses and seem 
indifferent about giving proof of them, I request a patient 
and attentive reading of the whole, from which I hope 
those hesitating will derive satisfaction; for it appears 
to me that the reasonings are so mutually connected in 
these treatises, that, as the last are demonstrated by the 
first which are their causes, the first are in their turn 
demonstrated by the last which are their effects. Nor 
must it be imagined that I here commit the fallacy 
which the logicians call a circle; for since experience 
renders the majority of these effects most certain, the 
causes from which I deduce them do not serve so much 
to establish their reality as to explain their existence; 
but on the contrary, the reality of the causes is established 
by the reality of the effects. Nor have I called them 
hypotheses with any other end in view except that it may 
be known that I think I am able to deduce them from 
those first truths which I have already expounded; and 
yet that I have expressly determined not to do so, to 
prevent a certain class of minds from thence taking 
occasion to build some extravagant philosophy upon what 
they may take to be my principles, and my being blamed 
for it. I refer to those who imagine that they can master 
in a day all that another has taken twenty years to think 
out, as soon as he has spoken two or three words to them 
on the subject; or who are the more liable to error and 
the less capable of perceiving truth in very proportion as 
they are more subtle and lively. As to the opinions 
which are truly and wholly mine, I offer no apology for 
them as new,— persuaded as I am that if their reasons 
be well considered they will be found to be so simple and 

Discourse on Method 6i 

so conformed to common sense as to appear less extra- 
ordinary and less paradoxical than any others which can 
be held on the same subjects; nor do I even boast of being 
the earliest discoverer of any of them, but only of having 
adopted them, neither because they had nor because they 
had not been held by others, but solely because reason 
has convinced me of their truth. 

Though artisans may not be able at once to execute 
the invention which is explained in the " Dioptrics/' I do 
not think that any one on that account is entitled to 
condemn it; for since address and practice are required 
in order so to make and adjust the machines described by 
me as not to overlook the smallest particular, I should 
not be less astonished if they succeeded on the first 
attempt than if a person were in one day to become an 
accomplished performer on the guitar, by merely having 
excellent sheets of music set up before him. And if I 
write in French, which is the language of my country, in 
preference to Latin, which is that of my preceptors, it is 
because I expect that those who make use of their un- 
prejudiced hatural reason" will "Fe~Bette^^^^^ my 
opinions than those who give heed to the writings of the 
ancients only ; and as for those who unite good sense with 
habits of study, whom alone I desire for judges, they will 
not, I feel assured, be so partial to Latin as to refuse to 
listen to my reasonings merely because I expound them 
in the vulgar tongue. 

In conclusion, I am unwilling here to say anything 
very specific of the progress which I expect to make for 
the future in the sciences, or to bind myself to the public 
by any promise which I am not certain of being able to 
fulfil; but this only will I say, that I have resolved to 
devote what time I may still have to live to no other 
occupation than that of endeavouring to acquire some 
knowledge of Nature, which shall be of such a kind as to 
enable us therefrom to deduce rules in medicine of greater 
certainty than those at present in use; and that my 
inclination is so much opposed to all other pursuits, 
especially to such as cannot be useful to some without 
being hurtful to others, that if, by any circumstances, 
I had been constrained to engage in such, I do not believe 

62 Discourse on Method 

that I should have been able to succeed. Of this I here 
make a public declaration, though well aware that it 
cannot serve to procure for me any consideration in the 
world, which, however, I do not in the least affect; and 
I shall always hold myself more obliged to those through 
whose favour I am permitted to enjoy my retirement 
without interruption than to any who might offer me the 
highest earthly preferments. 








Gentlemen^ — The motive which impels me to present this 
treatise to you is so reasonable^ and, when you shall learn 
its design, I am confident that you also will consider that 
there is ground so valid for your taking it under your protec- 
tion, that I can in no way better recommend it to you than 
by briefly stating the end which I proposed to myself in it. 
I have always been of opinion that the two questions 
respecting God and the soul were the chief of those that 
ought to be determined by help of philosophy rather than 
of theology; for although to us, the faithful, it be suffi- 
cient to hold as matters of faith, that the human soul 
does not perish with the body, and that God exists, it 
yet assuredly seems impossible ever to persuade infidels 
of the reality of any religion, or almost even any moral 
virtue, unless, first of all, those two things be proved to 
them by natural reason. And since in this life there are 
frequently greater rewards held out to vice than to virtue, 
few would prefer the right to the useful, if they were 
restrained neither by the fear of God nor the expectation 
of another life; and although it is quite true that the 
existence of God is to be believed since it is taught in the 
sacred Scriptures, and that, on the other hand, the sacred 
Scriptures are to be believed because they come from 
God (for since faith is a gift of God, the same Being who 
bestows grace to enable us to believe other things, can 
likewise impart of it to enable us to believe his own exist- 
ence), nevertheless, this cannot be submitted to infidels, 
who would consider that the reasoning proceeded in a 
circle. And, indeed, I have observed that you, with all 

65 E 

66 Meditations 

the other theologians, not only affirmed the sufficiency of 
natural reason for the proof of the existence of God, but 
also that it may be inferred from sacred Scripture, that 
the 'knowledge of God is much clearer than of many 
created things, and that it is really so easy of acquisition 
as to leave those who do not possess it blame-worthy. 
This is manifest from these words of the Book of Wisdom, 
chap, xiii., where it is said, Howheit they are not to he 
excused ; Jor if their understanding was so great that they 
could discern the world and the creatures, why did they not 
rather find out the Lord thereof? And in Romans, chap, i., it 
is said that they are without excuse ; and again, in the same 
place, by these words, — That which may be known oj God 
is manifest in them — we seem to be admonished that all 
which can be known of God may be made manifest by 
reasons obtained from no other source than the inspection 
of our own minds. I have, therefore, thought that it 
would not be unbecoming in me to inquire how and by 
what way, without going out of ourselves, God may be 
more easily and certainly known than the things of the 

And as regards the soul, although many have judged 
that its nature could not be easily discovered, and some 
have even ventured to say that human reason led to the 
conclusion that it perished with the body, and that the 
contrary opinion could be held through faith alone ; never- 
theless, since the Lateran Council, held under Leo X. (in 
session viii.), condemns these, and expressly enjoins ' 
Christian philosophers to refute their arguments, and 
establish the truth according to their ability, I have 
ventured to attempt it in this work. Moreover, I am 
aware that most of the irreligious deny the existence of 
God, and the distinctness of the human soul from the 
body, for no other reason than because these points, as 
they allege, have never as yet been demonstrated. Now, 
although I am by no means of their opinion, but, on the 
contrary, hold that almost all the proofs which have : 
been adduced on these questions by great men, possess, 
when rightly understood, the force of demonstrations, 
and that it is next to impossible to discover new, yet 
there is, I apprehend, no more useful service to be per- 

Dedication 67 

formed in philosophy^ than if some one were^ once for all, 
carefully to seek out the best of these reasons^ and ex- 
pound them so accurately and clearly that, for the future, 
it might be manifest to all that they are real demonstra- 
tions. And finally, since many persons were greatly 
desirous of this, who knew that I had cultivated a certain 
method of resolving all kinds of difficulties in the sciences, 
which is not indeed new (there being nothing older than 
truth), but of which they were aware I had made successful 
use in other instances, I judged it to be my duty to make 
trial of it also on the present matter. 

Now the sum of what I have been able to accomplish on 
the subject is contained in this treatise. Not that I here 
essayed to collect all the diverse reasons which might be 
adduced as proofs on this subject, for this does not seem 
to be necessary, unless on matters where no one proof of 
adequate certainty is to be had; but I treated the first 
and chief alone in such a manner that I should venture 
now to propose them as demonstrations of the highest 
certainty and evidence. And I will also add that they 
are such as to lead me to think that there is no way open to 
the mind of man by which proofs superior to them can 
ever be discovered; for the importance of the subject, 
and the glory of God, to which all this relates, constrain 
me to speak here somewhat more freely of myself than I 
have been accustomed to do. Nevertheless, whatever 
certitude and evidence I may find in these demonstra- 
tions, I cannot therefore persuade myself that they are 
level to the comprehension of all. But just as in 
geometry there are many of the demonstrations of 
Archimedes, Apollonius, Pappus, and others, which, 
though received by all as evident even and certain 
(because indeed they manifestly contain nothing which, 
considered by itself, it is not very easy to understand, 
and no consequents that are inaccurately related to their 
antecedents), are nevertheless understood by a very 
limited number, because they are somewhat long, and 
demand the whole attention of the reader: so in the same 
way, although I consider the demonstrations of which I 
here make use, to be equal or even superior to the geo- 
metrical in certitude and evidence, I am afraid, neverthe- 

68 Meditations 

less, that they will not be adequately understood by 
many, as well because they also are somewhat long and 
involved, as chiefly because they require the mind to be 
entirely free from prejudice, and able with ease to detach 
itself from the commerce of the senses. And, to speak 
the truth, the ability for metaphysical studies is less 
general than for those of geometry. And, besides, there 
is still this difference that, as in geometry, all are per- 
suaded that nothing is usually advanced of which there 
is not a certain demonstration, those but partially versed 
in it err more frequently in assenting to what is false, from 
a desire of seeming to understand it, than in denying 
what is true. In philosophy, on the other hand, where 
it is believed that all is doubtful, few sincerely give them- 
selves to the search after truth, and by far the greater 
number seek the reputation of bold thinkers by 
audaciously impugning such truths as are of the greatest 

Hence it is that, whatever force my reasonings may 
possesr, yet because they belong to philosophy, I do not 
expect they will have much effect on the minds of men, 
unless you extend to them your patronage and approval. 
But since your faculty is held in so great esteem by all, 
and since the name of Sorbonne is of such authority, 
that not only in matters of faith, but even also in what 
regards human philosophy, has the judgment of no other 
society, after the sacred councils, received so great 
deference, it being the universal conviction that it is 
impossible elsewhere to find greater perspicacity and 
solidity, or greater wisdom and integrity in giving judg- 
ment, I doubt not, — if you but condescend to pay so 
much regard to this treatise as to be willing, in the first 
place, to correct it (for, mindful not only of my humanity, 
but chiefly also of my ignorance, I do not afhrm that it is 
free from errors); in the second place, to supply what is 
wanting in it, to perfect what is incomplete, and to give 
more ample illustration where it is demanded, or at least 
to indicate these defects to myself that I may endeavour 
to remedy them; and, finally, when the reasonings con- 
tained in it, by which the existence of God and the dis- 
tinction of the human soul from the body are established, 

Dedication 69 

shall have been brought to such degree of perspicuity as 
to be esteemed exact demonstrations^ of which I am 
assured they admit, if you condescend to accord them 
the authority of your approbation, and render a public 
testimony of their truth and certainty, — I doubt not, I 
say, but that henceforward all the errors which have ever 
been entertained on these questions will very soon be 
effaced from the minds of men. For truth itself will 
readily lead the remainder of the ingenious and the 
learned to subscribe to your judgment; and your 
authority will cause the atheists, who are in general 
sciolists rather than ingenious or learned, to lay aside the 
spirit of contradiction, and lead them, perhaps, to do 
battle in their own persons for reasonings which they find 
considered demonstrations by all men of genius, lest they 
should seem not to understand them; and, finally, the 
rest of mankind will readily trust to so many testimonies, 
and there will no longer be any one who will venture to 
doubt either the existence of God or the real distinction 
of mind and body. It is for you, in your singular wisdom, 
to judge of the importance of the establishment of such 
beliefs [who are cognisant of the disorders which doubt 
of these truths produces].^ But it would not here become 
me to commend at greater length the cause of God and 
religion to you, who have always proved the strongest 
support of the Catholic Church. 

^ The square brackets, here and throughout the volume, are used 
to mark additions to the original of the revised French translation. 


I HAVE already slightly touched upon the questions 
respecting the existence of God and the nature of the 
human soul, in the Discourse on the Method of rightly 
conducting the Reason, and seeking truth in the Sciences, 
published in French in the year 1637; not, however, with 
the design of there treating of them fully, but only, as it 
were, in passing, that I might learn from the judgments 
of my readers in what way I should afterwards handle 
them: for these questions appeared to me to be of such 
moment as to be worthy of being considered more than 
once, and the path which I follow in discussing them is so 
little trodden, and so remote from the ordinary route, 
that I thought it would not be expedient to illustrate it at 
greater length in French, and in a discourse that might 
be read by all, lest even the more feeble minds should 
believe that this path might be entered upon by them. 

But, as in the discourse on Method, I had requested 
all who might find aught meriting censure in my writings, 
to do me the favour of pointing it out to me, I may state 
that no objections worthy of remark have been alleged 
against what I then said on these questions, except two, 
to which I will here briefly reply, before undertaking their 
more detailed discussion. 

The first objection is that though, while the human 
mind reflects on itself, it does not perceive^* that it is 
any other than a thinking thing, it does not follow that its 
nature or essence consists only in its being a thing which 
thinks; so that the word only shall exclude all other 
things which might also perhaps be said to pertain to the 
nature of the mind. 

To this objection I reply, that it was not my intention 

* See Note I. The numbers refer to the Notes, in which will be 
found some notices of the various terms throughout the volume 
that appeared to require a word of comment. 


72 Meditations 

in that place to exclude these according to the order of 
truth in the matter (of which I did not then treat), but 
only according to the order of thought (perception); so 
that my meaning was, that I clearly apprehended nothing, 
so far as I was conscious, as belonging to my essence, 
except that I was a thinking thing, or a thing possessing 
in itself the faculty of thinking. But I will show here- 
after how, from the consciousness that nothing besides 
thinking belongs to the essence of the mind, it follows 
that nothing else does in truth belong to it. 

The second objection is that it does not follow, from my 
possessing the idea of a thing more perfect than I am, that 
the idea itself is more perfect than myself, and much 
less that what is represented by the idea exists. 

But I reply that in the term idea ^ there is here some- 
thing equivocal; for it may be taken either materially 
for an act of the understanding, and in this sense it cannot 
be said to be more perfect than I, or objectively, for the 
thing represented by that act, which, although it be not 
supposed to exist out of my understanding, may, never- 
theleGS, be more perfect than myself, by reason of its 
essence. But, in the sequel of this treatise I will show 
more amply how, from my possessing the idea of a thing 
more perfect than myself, it follows that this thing really 

Besides these two objections, I have seen, indeed, two 
treatises of sufficient length relating to the present matter. 
In these, however, my conclusions, much more than my 
premises, were impugned, and that by arguments borrowed 
from the common-places of the atheists. But, as argu- 
ments of this sort can make no impression on the minds 
of those who shall rightly understand my reasonings, and 
as the judgments of many are so irrational and weak that 
they are persuaded rather by the opinions on a subject 
that are first presented to them, however false and opposed 
to reason they may be, than by a true and solid, but sub- 
sequently received, refutation of them, I am unwilling 
here to reply to these strictures from a dread of being, in 
the first instance, obliged to state them. 

I will only say, in general, that all which the atheists 
commonly allege in favour of the non-existence of God 

Preface to the Reader 73 

arises continually from one or other of these two things^ 
namely, either the ascription of human affections to deity, 
or the undue attribution to our minds of so much vigour 
j and wisdom that we may essay to determine and compre- 
hend both what God can and ought to do; hence all that 
is alleged by them will occasion us no difficulty, provided 
only we keep in remembrance that our minds must be 
considered finite, while Deity is incomprehensible and 

Now that I have once, in some measure, made proof of 
the opinions of men regarding my work, I again undertake 
to treat of God and the human soul, and at the same time 
to discuss the principles of the entire first philosophy, 
without, however, expecting any commendation from 
the crowd for my endeavours, or a wide circle of readers. 
On the contrary, I would advise none to read this work, 
unless such as are able and willing to meditate with me 
in earnest, to detach their minds from commerce with 
the senses, and likewise to deliver themselves from all 
prejudice; and individuals of this character are, I well 
know, remarkably rare. But with regard to those who, 
without caring to comprehend the order and connection 
of the reasonings, shall study only detached clauses for 
the purpose of small but noisy criticism, as is the custom 
with many, I may say that such persons will not profit 
greatly by the reading of this treatise; and although 
perhaps they may find opportunity for cavilling in several 
places, they will yet hardly start any pressing objections, 
or such as shall be deserving of reply. 

But since, indeed, I do not promise to satisfy others on 
all these subjects at first sight, nor arrogate so much to 
myself as to believe that I have been able to foresee all 
that may be the source of difficulty to each one, I shall 
expound, first of all, in the Meditations , those considera- 
tions by which I feel persuaded that I have arrived at a 
certain and evident knowledge of truth, in order that I 
may ascertain whether the reasonings which have pre- 
vailed with myself will also be effectual in convincing 
others. I will then reply to the objections of some men, 
illustrious for their genius and learning, to whom these 
meditations were sent for criticism before they were com- 

74 Meditations 

mitted to the press; for these objections are so numerous 
and varied that I venture to anticipate that nothing, at 
least nothing of any moment, will readily occur to any 
mind which has not been touched upon in them. 

Hence it is that I earnestly entreat my readers not to 
come to any judgment on the questions raised in the 
meditations until they have taken care to read the whole 
of the objections, with the relative replies. 




In the First Meditation I expound the grounds on which 
we may doubt in general of all things, and especially of 
material objects, so long, at least, as we have no other 
foundations for the sciences than those we have hitherto 
possessed. \\ Now, although the utility of a doubt so 
general may not be manifest at first sight, it is neverthe- 
less of the greatest, since it delivers us from all prejudice, 
and affords the easiest pathway by which the mind may 
withdraw itself from the senses; and, finally, makes it 
impossible for us to doubt wherever we afterwards dis- 
cover truth. ]'^ ^ 

In the Second, the mind which, in the exercise of the 
freedom peculiar to itself, supposes that no object is, of 
the existence of which it has even the slightest doubt, 
finds that, meanwhile, it must itself exist. And this 
point is likewise of the highest moment, for the mind is 
thus enabled easily to distinguish what pertains to itself, 
that is, to the intellectual nature, from what is to be 
referred to the body. But since some, perhaps, will 
expect, at this stage of our progress, a statement of the 
reasons which establish the doctrine of the immortality of 
the soul, I think it proper here to make such aware, that 
it was my aim to write nothing of which I could not give 
exact demonstration, and that I therefore felt myself 
obliged to adopt an order similar to that in use among the 
geometers, viz., to premise all upon which the proposition 
in question depends, before coming to any conclusion 
respecting it. Now% the first and chief .pre-requisite for 
the knowledge of the immortality of the soul is our being 
able to form the clearest possible conception {conceptus — 




concept) of the soul itself^ and such as shall be absolutely 
distinct from all our notions of body; and how this is 
to be accomplished is there shown. There is required, 
besides this, the assurance that all objects which we 
clearly and distinctly think are true (really exist) in that 
very mode in which we think them: and this could not 
be established previously to the Fourth Meditation. 
Farther, it is necessary, for the same purpose, that we 
possess a distinct conception of corporeal nature, which 
is given partly in the Second and partly in the Fifth and 
Sixth Meditations. And, finally, on these grounds, we 
are necessitated to conclude, that all those objects which 
are clearly and distinctly conceived to be diverse sub- 
stances, as mind and body, are substances really recipro- 
cally distinct; and this inference is made in the Sixth 
Meditation. The absolute distinction of mind and body 
is, besides, confirmed in this Second Meditation, by show- 
ing that we cannot conceive body unless as divisible; 
while, on the other hand, mind cannot be conceived 
unless as indivisible. For we are not able to conceive 
the half of a mind, as we can of any body, however small, 
so that the natures of these two substances are to be held, 
not only as diverse, but even in some measure as con- 
traries. I have not, however, pursued this discussion 
further in the present treatise, as well for the reason that 
these considerations are sufficient to show that the 
destruction of the mind does not follow from the cor- 
ruption of the body, and thus to afford to men the hope 
of a future life, as also because the premises from which 
it is competent for us to infer the immortality of the soul, 
involve an explication of the whole principles of physics : 
in order to establish, in the first place, that generally all 
substances, that is, all things which can exist only in con- 
sequence of having been created by God, are in their own 
nature incorruptible, and can never cease to be, unless 
God himself, by refusing his concurrence to them, reduce 
them to nothing; and, in the second place, that body, 
taken generally, is a substance, and therefore can never 
perish, but that the human body, in as far as it differs 
from other bodies, is constituted only by a certain con- 
figuration of members, and by other accidents of this sort. 

Synopsis 77 

while the human mind is not made up of accidents, but is a 
pure substance. For although all the accidents of the 
mind be changed — although, for example, it think certain 
things, will others, and perceive others, the mind itself 
does not vary with these changes; while, on the contrary, 
the human body is no longer the same if a change take 
place in the form of any of its parts : from which it follows 
that the body may, indeed, without difficulty perish, but 
that the mind is in its own nature immortal. 

In the Third Meditation, I have unfolded at sufficient 
length, as appears to me, my chief argument for the 
existence of God. But yet, since I was there desirous to 
avoid the use of comparisons taken from material objects, 
that I might withdraw, as far as possible, the minds of 
m}'' readers from the senses, numerous obscurities perhaps 
remain, which, however, will, I trust, be afterwards 
entirely removed in the replies to the objections: thus, 
among other things, it may be difficult to understand how 
the idea of a being absolutely perfect, which is found in 
our minds, possesses so much objective reality ^ [i.e., 
participates by representation in so many degrees of being 
and perfection] that it must be held to arise from a course 
absolutely perfect. This is illustrated in the replies by 
the comparison of a highly perfect machine, the idea of 
which exists in the mind of some workmen; for as the 
objective {i.e., representative) perfection of this idea 
must have some cause, viz., either the science of the 
workman, or of some other person from whom he has 
received the idea, in the same way the idea of God, 
which is found in us, demands God himself for its cause. 

In the Fourth, it is shown that all which we clearly and 
distinctly perceive (apprehend) is true; and, at the same 
time, is explained wherein consists the nature of error; 
points that require to be known as well for confirming the 
preceding truths, as for the better understanding of those 
that are to follow. But, meanwhile, it must be observed, 
that I do not at all there treat of Sin, that is, of error 
committed in the pursuit of good and evil, but of that sort 
alone which arises in the determination of the true and 
the false. Nor do I refer to matters of faith, or to the 
conduct of life, but only to what regards speculative 

yS Meditations , 

truths, and such as are known by means of the natural 
light aione. 

In the Fifth, besides the illustration of corporeal nature, 
taken generically, a new demonstration is given of the 
existence of God, not free, perhaps, any more than the 
former, from certain difficulties, but of these the solution 
will be found in the replies to the objections. I further 
show in what sense it is true that the certitude of geo- 
metrical demonstrations themselves is dependent on the 
knowledge of God. 

Finally, in the Sixth, the act of the understanding 
{intellectio) is distinguished from that of the imagination ' 
(tmaginatio); the marks of this distinction are described; 
the human mind is shown to be really distinct from the 
body, and, nevertheless, to be so closely conjoined there- 
with, as together to form, as it were, a unity. The whole 
of the errors which arise from the senses are brought 
under review, while the means of avoiding them are 
pointed out; and, finally, all the grounds are adduced 
from which the existence of material objects may be 
inferred; not, however, because I deemed them of great 
utility in establishing what they prove, viz., that there 
is in reality a world, that men are possessed of bodies, and 
the like, the truth of which no one of sound mind ever 
seriously doubted; but because, from a close considera- 
tion of them, it is perceived that they are neither so 
strong nor clear as the reasonings which conduct us to the 
knowledge of our mind and of God; so that the latter 
are, of all which come under human knowledge, the most 
certain and manifest — a conclusion which it was my 
single aim in these Meditations to establish; on which 
account I here omit mention of the various other ques- 
tions which, in the course of the discussion, I had occasion 
likewise to consider. 








Several years have now elapsed since I first became aware 
that I had accepted, even from my youth, many false 
opinions for true, and that consequently what I afterwards 
based on such principles was highly doubtful; and from 
that time I was convinced of the necessity of undertaking 
once in my life to rid myself of all the opinions I had 
adopted, and of commencing anew the work of building 
from the foundation, if I desired to establish a firm and 
abiding superstructure in the sciences. But as this enter- 
prise appeared to me to be one of great magnitude, I 
waited until I had attained an age so mature as to leave 
me no hope that at any stage of life more advanced I 
should be better able to execute my design. On this 
account, I have delayed so long that I should henceforth 
consider I was doing wrong were I still to consume in 
deliberation any of the time that now remains for action. 
To-day, then, since I have opportunely freed my mind 
from all cares [and am happily disturbed by no passions], 
and since I am in the secure possession of leisure in a 
peaceable retirement, I will at length apply myself 
earnestly and freely to the general overthrow of all my 


8o Meditations 

former opinions. But^ to this end, it will not be necessary 
for me to show that the whole of these are false — a point, 
perhaps, which I shall never reach; but as even now my 
reason convinces me that I ought not the less carefully to 
withhold belief from what is not entirely certain and 
indubitable, than from what is manifestly false, it will be 
sufficient to justify the rejection of the whole if I shall 
find in each some ground for doubt. Nor for this purpose 
will it be necessary even to deal with each belief individu- 
ally, which would be truly an endless labour; but, as the 
removal from below of the foundation necessarily involves 
the downfall of the whole edifice, I will at once approach 
the criticism of the principles on which all my former 
beliefs rested. 

All that I have, up to this moment, accepted as pos- 
sessed of the highest truth and certainty, I received either 
from or through the senses.^ I observed, however, that 
these sometimes misled us ; and it is the part of prudence 
not to place absolute confidence in that by which we have 
even once been deceived. 

But it may be said, perhaps, that, although the senses 
occasionally mislead us respecting minute objects, and such 
as are so far removed from us as to be beyond the reach 
of close observation, there are yet many other of their 
informations (presentations), of the truth of which it is 
manifestly impossible to doubt; as for example, that I am 
in this place, seated by the fire, clothed in a winter dress- 
ing-gown, that I hold in my hands this piece of paper, 
with other intimations cf the same nature. But how 
could I deny that I possess these hands and this body, and 
withal escape being classed with persons in a state of 
insanity, whose brains are so disordered and clouded by 
dark bilious vapours as to cause them pertinaciously to 
assert that they are monarchs when they are in the 
greatest poverty; or clothed [in gold] and purple when 
destitute of any covering; or that their head is made of 
clay, their body of glass, or that they are gourds? I 
should certainly be not less insane than they, were I to 
regulate my procedure according to examples so extra- 

Though this be true, I must nevertheless here consider 

Things We May Doubt 8 1 

that I am a man^ and that, consequently, I am in the 
habit of sleeping, and representing to myself in dreams 
those same things, or even sometimes others less probable, 
which the insane think are presented to them in their 
waking moments. How often have I dreamt that I was 
in these familiar circumstances — that I was dressed, and 
occupied this place by the fire, when I was lying undressed 
in bed? At the present moment, however, I certainly 
look upon this paper with eyes wide awake; the head 
which I now move is not asleep; I extend this hand con- 
sciously and with express purpose, and I perceive it; the 
occurrences in sleep are not so distinct as all this. But 
I cannot forget that, at other times, I have been deceived 
in sleep by similar illusions; and, attentively considering 
those cases, I perceive so clearly that there exist no certain 
marks by which the state of waking can ever be distin- 
guished from sleep, that I feel greatly astonished; and 
in amazement I almost persuade myself that I am now 

Let us suppose, then, that we are dreaming, and that 
all these particulars — namely, the opening of the eyes, the 
motion of the head, the forth-putting of the hands — are 
merely illusions; and even that we really possess neither 
an entire body nor hands such as we see. Nevertheless, 
it must be admitted at least that the objects which appear 
to us in sleep are, as it were, painted representations 
which could not have been formed unless in the likeness 
of realities; and, therefore, that those general objects, at 
all events — namely, eyes, a head, hands, and an entire 
body — are not simply imaginary, but really existent. 
For, in truth, painters themselves, even when they study 
to represent sirens and satyrs by forms the most fantastic 
and extraordinary, cannot bestow upon them natures 
absolutely new, but can only make a certain medley of 
the members of different animals; or if they chance to 
imagine something so novel that nothing at all similar 
has ever been seen before, and such as is, therefore, purely 
fictitious and absolutely false, it is at least certain that 
the colours of which this is composed are real. 

And on the same principle, although these general 
objects, viz. [a body], eyes, a head, hands, and the like, 


82 Meditations 

be imaginary, we are nevertheless absolutely necessitated 
to admit the reality at least of some other objects still 
more simple and universal than these, of which, just as of 
certain real colours, all those images of things, whether 
true and real, or false and fantastic, that are found in our 
consciousness {cogitatio),^ are formed. 

To this class of objects seem to belong corporeal nature 
in general and its extension; the figure of extended things, 
their quantity or magnitude, and their number, as also 
the place in, and the time during, which they exist, and 
other things of the same sort. We will not, therefore, 
perhaps reason illegitimately if we conclude from this 
that physics, astronomy, medicine, and all the other 
sciences that have for their end the consideration of com- 
posite objects, are indeed of a doubtful character; but 
that arithmetic, geometry, and the other sciences of the 
same class, which regard merely the simplest and most 
general objects, and scarcely inquire whether or not these 
are really existent, contain somewhat that is certain and 
indubitable: for whether I am awake or dreaming, it 
remains true that two and three make five, and that a 
square has but four sides; nor does it seem possible that 
truths so apparent can ever fall under a suspicion of 
falsity [or incertitude]. 

Nevertheless, the belief that there is a God who is all- 
powerful, and who created me, such as I am, has for a 
long time, obtained steady possession of my mind. How, 
then, do I know that he has not arranged that there 
should be neither earth, nor sky, nor any extended thing, 
nor figure, nor magnitude, nor place, providing at the 
same time, however, for [the rise in me of the perceptions 
of all these objects, and] the persuasion that these do not 
exist otherwise than as I perceive them? And further, 
as I sometimes think that others are in error respecting 
matters of which they believe themselves to possess a 
perfect knowledge, how do I know that I am not also 
deceived each time I add together two and three, or 
number the sides of a square, or form some judgment still 
more simple, if more simple indeed can be imagined.^ 
But perhaps Deity has not been willing that I should be 
thus deceived, for He is said to be supremely good. If, 

Things We May Doubt 83 

however, it were repugnant to the goodness of Deity to 
have created me subject to constant deception, it would 
seem Hkewise to be contrary to his goodness to allow me 
to be occasionally deceived; and yet it is clear that this 
is permitted. Some, indeed, might perhaps be found who 
would be disposed rather to deny the existence of a being 
so powerful than to believe that there is nothing certain. 
But let us for the present refrain from opposing this 
opinion, and grant that all which is here said of a Deity is 
fabulous: nevertheless, in whatever way it be supposed 
that I reached the state in which I exist, whether by fate, 
or chance, or by an endless series of antecedents and 
consequents, or by any other means, it is clear (since to 
be deceived and to err is a certain defect) that the pro- 
bability of my being so imperfect as to be the constant 
victim of deception, will be increased exactly in propor- 
tion as the power possessed by the cause, to which they 
assign my origin, is lessened. To these reasonings I have 
assuredly nothing to reply, but am constrained at last to 
avow that there is nothing at all that I formerly believed 
to be true of which it is impossible to doubt, and that not 
through thoughtlessness or levity, but from cogent and 
maturely considered reasons; so that henceforward, if I 
desire to discover anything certain, I ought not the less 
carefully to refrain from assenting to those same opinions 
than to what might be shown to be manifestly false. 

But it is not sufficient to have made these observations ; 
care must be taken likewise to keep them in remembrance. 
For those old and customary opinions perpetually recur — 
long and familiar usage giving them the right of occupying 
my mind, even almost against my will, and subduing my 
belief; nor will I lose the habit of deferring to them and 
confiding in them so long as I shall consider them to be 
what in truth they are, viz., opinions to some extent 
doubtful, as I have already shown, but still highly pro- 
bable, and such as it is much more reasonable to believe 
than deny. It is for this reason I am persuaded that I 
shall not be doing wrong, if, taking an opposite judgment 
of deliberate design, I become my own deceiver, by sup- 
posing, for a time, that all those opinions are entirely 
false and imaginary, until at length, having thus balanced 

84 Meditations 

my old by my new prejudices, my judgment shall no longer 
be turned aside by perverted usage from the path that 
may conduct to the perception of truth. For I am 
assured that, meanwhile, there will arise neither peril nor 
error from this course, and that I cannot for the present 
yield too much to distrust, since the end I now seek is 
not action but knowledge. 

I will suppose, then, not that Deity, who is sovereignly 
good and the fountain of truth, but that some malignant 
demon, who is at once exceedingly potent and deceitful, 
has employed all his artifice to deceive me; I will suppose 
that the sky, the air, the earth, colours, figures, sounds, 
and all external things, are nothing better than the illu- 
sions of dreams, by means of which this being has laid 
snares for my credulity; I will consider myself as without 
hands, eyes, flesh, blood, or any of the senses, and as 
falsely believing that I am possessed of these; I will 
continue resolutely fixed in this belief, and if indeed by 
this means it be not in my power to arrive at the know- 
ledge of truth, I shall at least do what is in my power, 
viz. [suspend my judgment], and guard with settled pur- 
pose against giving my assent to what is false, and being 
imposed upon by this deceiver, whatever be his power 
and artifice. 

But this undertaking is arduous, and a certain indolence 
insensibly leads me back to my ordinary course of life; 
and just as the captive, who, perchance, was enjoying in 
his dreams an imaginary liberty, when he begins to suspect 
that it is but a vision, dreads awakening, and conspires 
with the agreeable illusions that the deception may be 
prolonged; so I, of my own accord, fall back into the 
train of my former beliefs, and fear to arouse myself from 
my slumber, lest the time of laborious wakefulness that 
would succeed this quiet rest, in place of bringing any 
light of day, should prove inadequate to dispel the dark- 
ness that will arise from the difficulties that have now 
been raised. 



The Meditation of yesterday has filled my mind with so 
many doubts, that it is no longer in my power to forget 
them. Nor do I see, meanwhile, any principle on which 
they can be resolved; and, just as if I had fallen all of a 
sudden into very deep water, I am so greatly disconcerted 
as to be made unable either to plant my feet firmly on the 
bottom or sustain myself by swimming on the surface. I 
will, nevertheless, make an effort, and try anew the same 
path on which I had entered yesterday, that is, proceed 
by casting aside all that admits of the slightest doubt, not 
less than if I had discovered it to be absolutely false ; and 
I will continue always in this track until I shall find some- 
thing that is certain, or at least, if I can do nothing more, 
until I shall know with certainty that there is nothing 
certain. Archimedes, that he might transport the entire 
globe from the place it occupied to another, demanded 
only a point that was firm and immovable; so also, I 
shall be entitled to entertain the highest expectations, if 
I am fortunate enough to discover only one thing that is 
certain and indubitable. 

I suppose, accordingly, that all the things which I see 
are false (fictitious); I beheve that none of those objects 
which my fallacious memory represents ever existed; I 
suppose that I possess no senses; I beheve that body, 
figure, extension, motion, and place are merely fictions of 
my mind. What is there, then, that can be esteemed 
true? Perhaps this only, that there is absolutely nothing 

But how do I know that there is not something different 
altogether from the objects I have now enumerated, of 
which it is impossible to entertain the slightest doubt? 
Is there not a God, or some being, by whatever name I 


86 Meditations 

may designate him, who causes these thoughts to arise in 
my mind? But why suppose such a being, for it may be 
I myself am capable of producing them? Am I, then, at 
least not something ? But I before denied that I possessed 
senses or a body; I hesitate, however, for what follows 
from that? Am I so dependent on the body and the 
senses that without these I cannot exist? But I had 
the persuasion that there was absolutely nothing in the 
world, that there was no sky and no earth, neither minds 
nor bodies; was I not, therefore, at the same time, per- 
suaded that I did not exist? Far from it; I assuredly 
existed, since I was persuaded. But there is I know not 
what being, who is possessed at once of the highest power 
and the deepest cunning, who is constantly employing all 
his ingenuity in deceiving me. Doubtless, then, I exist, 
since I am deceived ; and, let him deceive me as he may, 
he can never bring it about that I am nothing, so long as 
I shall be conscious that I am something. So that it must, 
in fine, be maintained, all things being maturely and care- 
fully considered, that this proposition (pronunctaium) 1 
am,^ ^^t, is necessarily tjiie 
by me" or^conceived in my mind. 

^ But I do not yet know with sufficient clearness what I 
am, though assured that I am; and hence, in the next 
place, I must take care, lest perchance I inconsiderately 
substitute some other object in room of what is properly 
myself, and thus wander from truth, even in that know- 
ledge (cognition) which I hold to be of all others the most 
certain and evident. For this reason, I will now consider 
anew what I formerly believed myself to be, before I 
entered on the present train of thought; and of my 
previous opinion I will retrench all that can in the least 
be invalidated by the grounds of doubt I have adduced, 
in order that there may at length remain nothing but 
what is certain and indubitable. What then did I for- 
merly think I was? Undoubtedly I judged that I was a 
man. But what is a man ? Shall I say a rational animal ? 
Assuredly not; for it would be necessary forthwith to 
inquire into what is meant by animal, and what by 
rational, and thus, from a single question, I should insen- 
sibly glide into others, and these more difficult than the 

The Human Mind 87 

first; nor do I now possess enough of leisure to warrant 
me in wasting my time amid subtleties of this sort. I 
prefer here to attend to the thoughts that sprung up of 
themselves in my mind, and were inspired by my own 
nature alone, when I applied myself to the consideration 
of what I was. In the first place, then, I thought that I 
possessed a countenance, hands, arms, and all the fabric 
of members that appears in a corpse, and which I called 
by the name of body. It further occurred to me that I 
was nourished, that I walked, perceived, and thought, and 
all those actions I referred to the soul; but what the soul 
itself was I either did not stay to consider, or, if I did, I 
imagined that it was something extremely rare and subtile, 
like wind, or flame, or ether, spread through my grosser 
parts. As regarded the body, I did not even doubt of 
its nature, but thought I distinctly knew it, and if I had 
wished to describe it according to the notions I then 
entertained, I should have explained myself in this 
manner: B^^JbQd^.Ijaiider§taiid all that can be terminated 
by a certain figure; that can be comprised in a certain 
place, and so fill a certain space as therefrom to exclude 
every other body; that can be perceived either by touch, 
sight, hearing, taste, or smell; that can be moved in 
different ways, not indeed of itself, but by something 
foreign to it by which it is touched [and from which it 
receives the impression] ; for the power of self-motion, as 
likewise that of perceiving and thinking, I held as by no 
means pertaining to the n ature of body ; on the contrary, 
I was somewhat astonished to find such faculties existing 
in some bodies. 

But [as to myself, what can I now say that I am], since 
I suppose there exists an extremely powerful, and, if I 
may so speak, malignant being, whose whole endeavours 
are directed towards deceiving me? Can I affirm that I 
possess any one of all those attributes of which I have 
lately spoken as belonging to the nature of body? After 
attentively considering them in my own mind, I find 
none of them that can properly be said to belong to 
myself. To recount them were idle and tedious. Let 
us pass, then, to the attributes of the soul. The first 
mentioned were the powers of nutrition and walking; but, 

33 Meditations 

if it be true that I have no body, it is true likewise that 
I am capable neither of walking nor of being nounshed. 
Perception is another attribute of the soul; but percep- 
tion too is impossible without the body: besides, I have 
frequently, during sleep, believed that I perceived objects 
which I afterwards observed I did not m reality perceive. 
Thinking is another attribute of the soul; and here I 
discover^'what properly belongs to myself. This alone is 
inseparable from me. lam— I exist: this is certain; but 
how often? As often as I think; for perhaps it would 
even happen, if I should wholly cease to think, that I 
should at the same time altogether cease to be. I now 
admit nothing that is not necessarily true: I am there- 
fore, precisely speaking, only a thinking thing, that is, 
a mind {mens sive animus), understanding, or reason, — 
terms whose signification was before unknown to me. I 
am, however, a real thing, and really existent; but what 
thing? The answer was, a thinking thing. The ques- 
tion now arises, am I aught besides? I will stimulate 
my imagination with a view to discover whether I am 
not still something more than a thinking being. Now it 
is plain I am not the assemblage of members called the 
human body; I am not a thin and penetrating air diffused 
through all these members, or wind, or flame, or vapour, 
or breath, or any of all the things I can imagine; for I 
supposed that all these were not, and, without changing 
the supposition, I find that I still feel assured of my 

But it is true, perhaps, that those very things which I 
suppose to be non-existent, because they are unknown 
to me, are not in truth different from myself whom I know. 
This is a point I cannot determine, and do not now enter 
into any dispute regarding it. I can only judge of things 
that are known to me : I am conscious that I exist, and I 
who know that I exist inquire into what I am. It is, 
however, perfectly certain that the knowledge of my 
existence, thus precisely taken, is not dependent on things, 
the existence of which is as yet unknown to me: and 
consequently it is not dependent on any of the things I 
can feign in imagination. Moreover, the phrase itself, 
I frame an image (effingo), reminds me of my error; for I 

The Human Mind 89 

should in truth frame one if I were to imagine myself to 
be anything^ since to imagine is nothing more than to con- 
template the figure or image of a corporeal thing; but I 
already know that I exist, and that it is possible at the 
same time that all those images, and in general all that 
relates to the nature of body, are merely dreams [or 
chimeras]. From this I discover that it is not more 
reasonable to say, I will excite my imagination that I 
may know more distinctly what I am, than to express 
myself as follows: I am now awake, and perceive some- 
thing real; but because my perception is not sufficiently 
clear, I will of express purpose go to sleep that my dreams 
may represent to me the object of my perception with 
more truth and clearness. And, therefore, I know that 
nothing of all that I can embrace in imagination belongs 
to the knowledge which I have of myself, and that there 
is need to recall with the utmost care the mind from this 
mode of thinking, that it may be able to know its own 
nature with perfect distinctness. 

But what, then, am I ? A thinking thing, it has been 
said. But what is a thinking thing? It is a thing that 
doubts, understands [conceives], affirms, denies, wills, 
refuses, that imagines also, and perceives. Assuredly it 
is not little, if all these properties belong to my nature. 
But why should they not belong to it? Am I not that 
very being who no\^ doubts of almost everything; who, 
for all that, understands and conceives certain things, 
who affirms one alone as true, and denies the others ; who 
desires to know more of them, and does not wish to be 
deceived; who imagines many things, sometimes even 
despite his will; and is likewise percipient of many, as if 
through the medium of the senses. Is there nothing of 
all this as true as that I am, even although I should be 
always dreaming, and although he who gave me being 
employed all his ingenuity to deceive me? Is there also 
any one of these attributes that can be properly distin- 
guished from my thought, or that can be said to be 
separate from myself? For it is of itself so evident that 
it is I who doubt, I who understand, and I who desire, 
that it is here unnecessary to add anything by way of 
rendering it more clear. And I am as certainly the same 

go Meditations 

being who imagines; for, although it may be (as I before 
supposed) that nothing I imagine is true, still the power of 
imagination does not cease really to exist in me and to 
form part of my thoughts. In fine, I am the same being 
who perceives, that is, who apprehends certain objects as 
by the organs of sense, since, in truth, I see light, hear a 
noise, and feel heat. But it will be said that these pre- 
sentations are false, and that I am dreaming. Let it be 
so. At all events it is certain that I seem to see light, 
hear a noise, and feel heat; this cannot be false, and this 
is what in me is properly called perceiving (senttre), which 
is nothing else than thinking. From this I begin to know 
what I am with somewhat greater clearness and distinct- 
ness than heretofore. 

But, nevertheless, it still seems to me, and I cannot 
help beheving, that corporeal things, whose images are 
formed by thought [which fall under the senses], and are 
examined by the same, are known with much greater dis- 
tinctness than that I know not what part of myself 
which is not imaginable; although, in truth, it may seem 
strange to say that I know and comprehend with greater 
distinctness things whose existence appears to me doubtful, 
that are unknown, and do not belong to me, than others 
of whose reality I am persuaded, that are known to me, 
and appertain to my proper nature; in a word, than 
myself. But I see clearly what is t^e state of the case. 
My m ind is apt jto-,wa^nder, and will not yet submit to be 
restrainea"''withinjbe limfts^ of ^truth7~~terus^ therefore 
leUve^he mirid^o itself once mDre^ and, according to it 
every kind of liberty [permit it to consider the objects 
that appear to it from without], in order that, having 
afterwards withdrawn it from these gently and oppor- 
tunely [and fixed it on the consideration of its being and 
the properties it finds in itself], it may then be the more 
easily controlled. 
)r" Let us now accordingly consider the objects that are 
/commonly thought to be [the most easily, and likewise] 
I J the most distinctly known, viz., the bodies we touch and 
I "see; not, indeed, bodies in general, for these general 
/notions are usually somewhat more confused, but one 
i body in particular. Take, for example, this piece of wax; 

The Human Mind 91 

it is quite fresh, having been but recently taken from the 
beehive; it has not yet lost the sweetness of the honey it 
contained; it still retains somewhat of the odour of the 
flowers from which it was gathered; its colour, figure, 
size, are apparent (to the sight); it is hard, cold, easily 
handled; and sounds when struck upon with the finger. 
In fine, all that contributes to make a body as distinctly 
known as possible, is found in the one before us. But, 
while I am speaking, let it be placed near the fire — what 
remained of the taste exhales, the smell evaporates, the 
colour changes, its figure is destroyed, its size increases, it 
becomes liquid, it grows hot, it can hardly be handled, 
and, although struck upon, it emits no sound. Does the 
same wax still remain after this change? It must be 
admitted that it does remain; no one doubts it, or judges 
otherwise. What, then, was it I knew with so much 
distinctness in the piece of wax? Assuredly, it could be 
nothing of all that I observed by means of the senses, 
since all the things that fell under taste, smell, sight, 
touch, and hearing are changed, and yet the same wax 
remains. It was perhaps what I now think, viz., that 
this wax was neither the sweetness of honey, the pleasant 
odour of flowers, the whiteness, the figure, nor the sound, 
but only a body that a little before appeared to me con- 
spicuous under these forms, and which is now perceived 
under others. But, to speak precisely, what is it that I 
imagine when I think of it in this way? Let it be atten- 
tively considered, and, retrenching all that does not 
belong to the wax, let us see what remains. There cer- 
tainly remains nothing, except something extended, 
flexible, and movable. But what is meant by flexible 
and movable? Is it not that I imagine that the piece of 
wax, being round, is capable of becoming square, or of 
passing from a square into a triangular figure ? Assuredly 
such is not the case, because I conceive that it admits of 
an infinity of similar changes; and I am, moreover, 
unable to compass this infinity by imagination, and con- 
sequently this conception which I have of the wax is not 
the product of the faculty of imagination. But what 
now is this extension? Is it not also unknown? for it 
becomes greater when the wax is melted, greater when it 

gz Meditations 

is boiled, and greater still when the heat increases; and I 
should not conceive [clearly and] according to truth, the 
wax as it is, if I did not suppose that the piece we are con- 
sidering admitted even of a wider variety of extension 
than I ever imagined. I must, therefore, admit that I 
cannot even comprehend by imagination what the piece 
of wax is, and that it is the mind alone {mens, Lat.; 
entendement, F.) which perceives it. I speak of one piece 
in particular; for, as to wax in general, this is still more 
evident. But what is the piece of wax that can be per- 
ceived only by the [understanding of] mind? It is cer- 
tainly the same which I see, touch, imagine; and, in fine, 
it is the same which, from the beginning, I believed it to 
be. But (and this it is of moment to observe) the per- 
ception of it is neither an act of sight, of touch, nor of 
imagination, and never was either of these, though it 
might formerly seem so, but is simply an intuition 
{inspectio) of the mind, which may be imperfect and 
confused, as it formerly was, or very clear and distinct, as 
it is at present, according as the attention is more or less 
directed to the elements which it contains, and of which it 
is composed. 

But, meanwhile, I feel greatly astonished when I 
observe [the weakness of my mind, and] its proneness to 
error. For although, without at all giving expression to 
what I think, I consider all this in my own mind, words 
yet occasionally impede my progress, and I am almost 
led into error by the terms of ordinary language. We 
say, for example, that we see the same wax when it is 
before us, and not that we judge it to be the same from 
its retaining the same colour and figure: whence I should 
forthwith be disposed to conclude that the wax is known 
by the act of sight, and not by the intuition of the mind 
alone, were it not for the analogous instance of human 
beings passing on in the street below, as observed from a 
window. In this case I do not fail to say that I see the 
men themselves, just as I say that I see the wax; and yet 
what do I see from the window beyond hats and cloaks 
that might cover artificial machines, whose motions 
might be determined by springs ? But I judge that there 
are human beings from these appearances, and thus I 

The Human Mind 93 

comprehend, by the faculty of judgment alone which is 
in the mind, what I beheved I saw with my eyes. 

The man who makes it his aim to rise to knowledge 
superior to the common, ought to be ashamed to seek 
occasions of doubting from the vulgar forms of speech: 
instead, therefore, of doing this, I shall proceed with the 
matter in hand, and inquire whether I had a clearer and 
more perfect perception of the piece of wax when I first 
saw it, and when I thought I knew it by means of the 
external sense itself, or, at all events, by the common 
sense (sensus communis), as it is called, that is, by the 
imaginative faculty; or whether I rather apprehend it 
more clearly at present, after having examined with 
greater care, both what it is, and in what way it can be 
known. It would certainly be ridiculous to entertain any 
doubt on this point. For what, in that first perception, 
was there distinct? What did I perceive which any 
animal might not have perceived.^ But when I distin- 
guish the wax from its exterior forms, and when, as if I 
had stripped it of its vestments, I consider it quite naked, 
it is certain, although some error may still be found in 
my judgment, that I cannot, nevertheless, thus apprehend 
it without possessing a human mind. 

But, finally, what shall I say of the mind itself, that is, 
of myself.^ for as yet I do not admit that I am anything 
but mind. What, then! I who seem to possess so dis- 
tinct an apprehension of the piece of wax, — do I not know 
myself, both with greater truth and certitude, and also 
much more distinctly and clearly? For if I judge that 
the wax exists because I see it, it assuredly follows, 
much more evidently, that I myself am or exist, for the 
same reason: for it is possible that what I see may not in 
truth be wax, and that I do not even possess eyes with 
which to see anything; but it cannot be that when I see, 
or, which comes to the same thing, when I think I see, I 
myself who think am nothing. So likewise, if I judge 
that the wax exists because I touch it, it will still also 
follow that I am; and if I determine that my imagina- 
tion, or any other cause, whatever it be, persuades me of 
the existence of the wax, I will still draw the same con- 
clusion. And what is here remarked of the piece of wax 

94 Meditations 

is applicable to all the other things that are external to 
me. And further^ if the [notion or] perception of wax 
appeared to me more precise and distinct, after that not 
only sight and touch, but many other causes besides, 
rendered it manifest to my apprehension, with how much 
greater distinctness must I now know myself, since all 
the reasons that contribute to the knowledge of the nature 
of wax, or of any body whatever, manifest still better the 
nature of my mind ? And there are besides so many other 
things in the mind itself that contribute to the illus- 
tration of its nature, that those dependent on the body, 
to which I have here referred, scarcely merit to be taken 
into account. 

But, in conclusion, I find I have insensibly reverted 
to the point I desired; for, since it is now manifest to 
me that bodies themselves are not properly perceived by 
the senses nor by the faculty of imagination, but by the 
intellect alone; and since they are not perceived because 
they are seen and touched, but only because they are 
understood [or rightly comprehended by thought], I 
readily discover that there is nothing more easily or 
clearly apprehended than my own mind. But because 
it is difficult to rid one's self so promptly of an opinion to 
which one has been long accustomed, it will be desirable 
to tarry for some time at this stage, that, by long con- 
tinued meditation, I may more deeply impress upon my 
memory this new knowledge. 


OF god: that he exists 

I WILL now close my eyes, I will stop my ears, I will turn 
away my senses from their objects, I will even efface from 
my consciousness all the images of corporeal things; or 
at least, because this can hardly be accomplished, I will 
consider them as empty and false; and thus, holding 
converse only with myself, and closely examining my 
nature, I will endeavour to obtain by degrees a more 
intimate and familiar knowledge of myself. I am a 
thinking (conscious) thing, that is, a being who doubts, 
affirms, denies, knows a few objects, and is ignorant of 
many, — [who loves, hates], wills, refuses, — who imagines 
likewise, and perceives; for, as I before remarked, 
although the things which I perceive or imagine are 
perhaps nothing at all apart from me [and in themselves], 
I am nevertheless assured that those modes of conscious- 
ness which I call perceptions and imaginations, in as far 
only as they are modes of consciousness, exist in me. 
And in the little I have said I think I have summed up 
all that I really know, or at least all that up to this time 
I was aware I knew. Now, as I am endeavouring to 
extend my knowledge more widely, I will use circum- 
spection, and consider with care whether I can still dis- 
cover in myself anything further which I have not yet 
hitherto observed. I am certain that I am a thinking 
thing; but do I not therefore likewise know what is 
required to render me certain of a truth? In this first 
knowledge, doubtless, there is nothing that gives me 
assurance of its truth except the clear and distinct per- 
ception of what I affirm, which would not indeed be 
sufficient to give me the assurance that what I say is true, 
if it could ever happen that anything I thus clearly and 
distinctly perceived should prove false; and accordingly 
it seems to me that I may now take as a general rule^ that 


g6 Meditations 

all that is very clearly and distinctly apprehended (con- 
ceived) is true. 

Nevertheless I before received and admitted many 
things as wholly certain and manifest, which yet I after- 
wards found to be doubtful. What, then, were those? 
They were the earth, the sky, the stars, and all the other 
objects which I was in the habit of perceiving by the 
senses. But what was it that I clearly [and distinctly] 
perceived in them? Nothing more than that the ideas 
and the thoughts of those objects were presented to my 
mind. And even now I do not deny that these ideas are 
found in my mind. But there was yet another thing 
which I affirmed, and which, from having been accustomed 
to believe it, I thought I clearly perceived, although, in 
truth, I did not perceive it at all; I mean the existence 
of objects external to me, from which those ideas pro- 
ceeded, and to which they had a perfect resemblance; 
and it was here I was mistaken, or if I judged correctly, 
this assuredly was not to be traced to any knowledge I 
possessed (the force of my perception, Lat.). 

But when I considered any matter in arithmetic and 
geometry, that was very simple and easy, as, for example, 
that two and three added together make five, and things 
of this sort, did I not view them with at least sufficient 
clearness to warrant me in affirming their truth ? Indeed, 
if I afterwards judged that we ought to doubt of these 
things, it was for no other reason than because it occu rred 
to me that a God might perhaps have given me such a 
nature as that I should be deceived, even respecting the 
matters that appeared to me the most evidently true. 
But as often as this preconceived opinion of the sovereign 
power of a God presents itself to my mind, I am con- 
strained to admit that it is easy for him, if he wishes it, 
to cause me to err, even in matters where I think I possess 
the highest evidence; and, on the other hand, as often 
as I direct my attention to things which I think I appre- 
hend with great clearness I am so persuaded of their truth 
that I naturally break out into expressions such as these: 
Deceive me who may, no one will yet ever be able to 
bring it about that I am not, so long as I shall be conscious 
that I am, or at any future time cause it to be true that 

Of God : That He Exists 97 

I have never been, it being now true that I am, or make 
two and three more or less than five, in supposing which 
and other like absurdities, I discover a manifest contra- 

And in truth, as I have no ground for believing that 
Deity is deceitful, and as, indeed, I have not even con- 
sidered the reasons by which the existence of a Deity of 
any kind is established, the ground of doubt that rests 
only on this supposition is very slight, and, so to speak, 
metaphysical. But, that I may be able wholly to remove 
it, I must inquire whether there is a God, as soon as an 
opportunity of doing so shall present itself; and if I find 
that there is a God, I must examine likewise whether he 
can be a deceiver; for, without the knowledge of these 
I two truths, I do not see that I can ever be certain of any- 
1 thing. And that I may be enabled to examine this 
I without interrupting the order of meditation I have 
proposed to myself [which is, to pass by degrees from the 
notions that I shall find first in my mind to those I shall 
afterwards discover in it], it is necessary at this stage to 
divide all my thoughts into certain classes, and to consider 
in which of these classes truth and error are, strictly 
speaking, to be found. 

Of my thoughts some are, as it were, images of things, 
and to these alone properly belongs the name idea ; as 
when I think [represent to my mind] a man, a chimera, 
the sky, an angel, or God. Others, again, have certain 
other forms ; as when I will, fear, affirm, or deny, I always, 
indeed, apprehend something as the object of my thought, 
but I also embrace in thought something more than the 
representation of the object; and of this class of thoughts 
some are called volitions or affections, and others judg- 

Now, with respect to ideas, if these are considered only 
in themselves, and are not referred to any object beyond 
them, they cannot, properly speaking, be false; for 
whether I imagine a goat or a chimera, it is not less true 
that I imagine the one than the other. Nor need we fear 
that falsity may exist in the will or affections; for, al- 
though I may desire objects that are wrong, and even that 
never existed, it is still true that I desire them. There thus 




only remain our judgments, in which we must take diligent 
heed that we be not deceived. But the chief and most 
ordinary error that arises in them consists in judging that 
the ideas which are in us are like or conformed to the things 
that are external to us; for assuredly, if we but considered 
the ideas themselves as certain modes of our thought 
(consciousness), without referring them to anything 
beyond, they would hardly afford any occasion of error. 

But, among these ideas, some appear to me to be innate,* 
others adventitious, and others to be made by myself 
(factitious); for, as I have the power of conceiving what 
is called a thing, or a truth, or a thought, it seems to me 
that I hold this power from no other source than my own 
nature; but if I now hear a noise, if I see the sun, or if 
I feel heat, I have all along judged that these sensations 
proceeded from certain objects existing out of myself; 
and, in fine, it appears to me that sirens, hippogryphs, and 
the like, are inventions of my own mind. But I may even 
perhaps come to be of opinion that all my ideas are of 
the class which I call adventitious, or that they are all 
innate, or that they are all factitious, for I have not yet 
clearly discovered their true origin; and what I have 
here principally to do is to consider, with reference to 
those that appear to come from certain objects without 
me, what grounds there are for thinking them like these 

The first of these grounds is that it seems to me I am 
so taught by nature; and the second that I am conscious 
that those ideas are not dependent on my will, and there- 
fore not on myself, for they are frequently presented to 
me against my will, — as at present, whether I will or not, 
I feel heat; and I am thus persuaded that this sensation 
or idea (sensum vel ideam) of heat is produced in me by 
something different from myself, viz., by the heat of the 
fire by which I sit. And it is very reasonable to suppose 
that this object impresses me with its own likeness rather 
than any other thing. 

^ But I must consider whether these reasons are suffi- 
ciently strong and convincing. When I speak of being 
taught by nature in this matter, I understand by the word 
nature only a certain spontaneous impetus that impels 

Of God : That He Exists 


me to believe in a resemblance between ideas and their 
objects, and not a natural light that affords a knowledge 
of its truth. But these two things are widely different; 
for what the natural light shows to be true can be in no 
degree doubtful, as, for example, that I am because I 
doubt, and other truths of the like kind : inasmuch as I 
possess no other faculty whereby to distinguish truth 
from error, which can teach me the falsity of what the 
natural light declares to be true, and which is equally trust- 
worthy; but with respect to [seemingly] natural impulses, 
I have observed, when the question related to the choice of 
right or wrong in action, that they frequently led me to 
take the worse part; nor do I see that I have any better 
ground for following them in what relates to truth and 
error. Then, with respect to the other reason, which is 
that because these ideas do not depend on my will, they 
must arise from objects existing without me, I do not find 
it more convincing than the former; for, just as those 
natural impulses, of which I have lately spoken, are 
found in me, notwithstanding that they are not always 
in harmony with my will, so likewise it may be that I 
possess some power not sufficiently known to myself 
capable of producing ideas without the aid of external 
objects, and, indeed, it has always hitherto appeared to 
me that they are formed during sleep, by some power of 
this nature, without the aid of aught external. And, in 
fine, although I should grant that they proceeded from 
those objects, it is not a necessary consequence that they 
must be like them. On the contrary, I have observed, 
in a number of instances, that there was a great difference 
between the object and its idea. Thus, for example, I 
find in my mind two wholly diverse ideas of the sun; the 
one, by which it appears to me extremely small, draws 
its origin from the senses, and should be placed in the 
class of adventitious ideas ; the other, by which it seem.s 
to be many times larger than the whole earth, is taken 
up on astronomical grounds, that is, elicited from certain 
notions bom with me, or is framed by myself in some other 
manner. These two ideas cannot certainly both resemble 
the same sun; and reason teaches me that the one which 
seems to have immediately emanated from it is the most 

lOo Meditations 

unlike. And these things sufficiently prove that hitherto 
it has not been from a certain and deliberate judgment, 
but only from a sort of blind impulse, that I believed in 
the existence of certain things different from myself, 
which, by the organs of sense, or by whatever other 
means it might be, conveyed their ideas or images into 
my mind [and impressed it with their likenesses]. 

But there is still another way of inquinng whether, of 
the objects whose ideas are in my mind, there are any that 
exist out of me. If ideas are taken in so far only as they 
are certain modes of consciousness, I do not remark^any 
difTerence or inequality among them, and all seemfin the 
same manner, to proceed from myself ; but, considering 
them as images, of which one represents one thing and 
another a different, it is evident that a great diversity 
obtains among them. For, without doubt^ those that 
represent substances are something more, and contain in 
themselves, so to speak, more objective reality [that is, 
participate by representation in higher degrees of being 
or perfection] than those that represent only modes or 
accidents ; and again, the idea by which I conceive a God 
[sovereign], eternal, infinite [immutable], all -knowing, 
all-powerful, and the creator of all things that are out of 
himself, — this, I say, has certainly in it more objective 
reality than those ideas by which finite substances are 

Now, it is manifest by the natural light that there must 
at least be as much reality in the efficient and total cause 
as in its effect; for whence can. the-^ffect^dxaAvJit^^ 
if not from its cause? and how could.ttie cause .communi- 
cate to it this reality unless it possessed it in itself? And 
hence it follows, not only that what is cannot be produced 
by what is not, but likewise thaft!Te~more "perfect, — in 
other words, that which contains in itself more reality, — 
cannot be the effect of the less perfect: and this is not 
only evidently true of those effects, whose reality is actual 
or formal, but likewise of ideas, whose reality is only con- 
sidered as objective. Thus, for example, the stone that 
is not yet in existence, not only cannot now commence to 
be, unless it be produced by that which possesses in itself, 
formally or eminently,^ all that enters into its composi- 

Of God: That He Exists loi 

tion [in other words, by that which contains in itself the 
same properties that are in the stone, or others superior 
to them]; and heat can only be produced in a subject 
that was before devoid of it, by a cause that is of an order 
[degree or kind] at least as perfect as heat; and so of the 
others. But further, even the idea of the heat, or of the 
stone, cannot exist in me unless it be put there by a cause 
that contains, at least, as much reality as I conceive 
existent in the heat or in the stone: for, although that 
cause may not transmit into my idea anything of its actual 
or formal reality, we ought not on this account to imagine 
that it is less real; but we ought to consider that [as 
every idea is a work of the mind], its nature is such as of 
itself to demand no other formal reality than that which it 
borrows from our consciousness, of which it is but a mode 
[that is, a manner or way of thinking]. But in order that 
an idea may contain this objective reality rather than 
that, it m.ust doubtless derive it from some cause in which 
is found at least as much formal reality as the idea con- 
tains an objective; for, if we suppose that there is found 
in an idea anything which was not in its cause, it must of 
course derive this from nothing. But, however imperfect 
may be the mode of existence by which a thing is objec- 
tively [or by representation] in the understanding by its 
idea, we certainly cannot, for all that, allege that this 
mode of existence is nothing, nor, consequently, that the 
idea owes its origin to nothing. Nor must it be imagined 
that, since the reality which is considered in these ideas 
is only objective, the same reality need not be formally 
(actually) in the causes of these ideas, but only objec- 
tively; for, just as the mode of existing objectively 
belongs to ideas by their peculiar nature, so likewise the 
mode of existing formally appertains to the causes of 
these ideas (at least to the first and principal), by their 
peculiar nature. And although an idea may give rise to 
another idea, this regress cannot, nevertheless, be infinite ; 
we must in the end reach a first idea, the cause of which 
is, as it were, the archetype in which all the reality [or 
perfection] that is found objectively [or by representa- 
tion] in these ideas is contained formally [and in act], 
I am thus clearly taught by the natural light that ideas 

I02 Meditations 

exist in me as pictures or images, which may in truth 
readily fall short of the perfection of the objects from 
which they are taken, but can never contain anything 
greater or more perfect. 

And in proportion to the time and care with which I 
examine all those matters, the conviction of their truth 
brightens and becomes distinct. But, to sum up, what 
^ conclusion shall I draw from it all? it is this; — if the 
objective reality [or perfection] of any one of my ideas 
be such as clearly to convince me, that this same reality 
exists in me neither formally nor eminently, and if, as 
follows from this, I myself cannot be the cause of it, it 
is a necessary consequence that I am not alone in the 
world, but that there is besides myself some other being 
who exists as the cause of that idea; while, on the con- 
trary, if no such idea be found in my mind, I shall have 
no sufficient ground of assurance of the existence of any 
other being besides myself, for, after a most careful 
search, I have, up to this moment, been unable to discover 
any other ground. \ 

But, among these my ideas, besides that which repre- 
sents myself, respecting which there can be here no 
difficulty, there is one that represents a God; others that 
represent corporeal and inanimate things; others angels; 
others animals ; and, finally, there are some that represent 
men like myself. But with respect to the ideas that 
represent other men, or animals, or angels, I can easily 
suppose that they were formed by the mingling and com- 
position of the other ideas which I have of myself, of 
corporeal things, and of God, although there were, apart 
from myself, neither men, animals, nor angels. And with 
regard to the ideas of corporeal objects, I never dis- 
covered in them anything so great or excellent which I 
myself did not appear capable of originating; for, by 
considering these ideas closely and scrutinising them 
individually, in the same way that I yesterday examined 
the idea of wax, I find that there is but little in them that 
is clearly and distinctly perceived. As belonging to the 
class of things that are clearly apprehended, I recognise 
the following, viz., magnitude or extension in length, 
breadth, and depth; figure, which results from the 

Of God: That He Exists 103 

termination of extension; situation, which bodies of 
diverse figures preserve with reference to each other; and 
motion or the change of situation; to which may be added 
substance, duration, and number. But with regard to 
light, colours, sounds, odours, tastes, heat, cold and the 
other tactile qualities, they are thought with so much 
obscurity and confusion, that I cannot determine even 
whether they are true or false; in other words, whether 
or not the ideas I have of these qualities are in truth the 
ideas of real objects. For although I before remarked 
that it is only in judgments that formal falsity, or falsity 
properly so called, can be met with, there may neverthe- 
less be found in ideas a certain material falsity, which 
arises when they represent what is nothing as if it were 
something. Thus, for example, the ideas I have of cold 
and heat are so far from being clear and distinct, that I 
am unable from them to discover whether cold is only 
the privation of heat, or heat the privation of cold; or 
whether they are or are not real qualities: and since, 
ideas being as it were images, there can be none that does 
not seem to us to represent some object, the idea which 
represents cold as something real and positive will not 
improperly be called false, if it be correct to say that cold 
is nothing but a privation of heat; and so in other cases. 
To ideas of this kind, indeed, it is not necessary that I 
should assign any author besides myself: for if they are 
false, that is, represent objects that are unreal, the natural 
light teaches me that they proceed from nothing; in other 
words, that they are in me only because something is 
wanting to the perfection of my nature; but if these ideas 
are true, yet because they exhibit to me so little reality 
that I cannot even distinguish the object represented from 
non-being, I do not see why I should not be the author 
of them. 

With reference to those ideas of corporeal things that 
are clear and distinct, there are some which, as appears 
to me, might have been taken from the idea I have of 
myself, as those of substance, duration, number, and the 
like. For when I think that a stone is a substance, or a 
thing capable of existing of itself, and that I am likewise 
a substance, although I conceive that I am a thinking and 

I04 Meditations 

non-extended thing, and that the stone, on the contrary, 
is extended and unconscious, there being thus the greatest 
diversity between the two concepts, — yet these two ideas 
seem to have this in common that they both represent 
substances. In the same way, when I think of myself as 
now existing, and recollect besides that I existed some 
time ago, and when I am conscious of various thoughts 
whose number I know, I then acquire the ideas of duration 
and number, which I can afterwards transfer to as many 
objects as I please. With respect to the other qualities 
that go to make up the ideas of corporeal objects, viz., 
extension, figure, situation, and motion, it is true that 
they are not formally in me, since I am merely a thinking 
being; but because they are only certain modes of sub- 
stance, and because I myself am a substance, it seems 
possible that they may be contained in me eminently. 

There only remains, therefore, the idea of God, in which 
I must consider whether there is anything that cannot be 
supposed to originate with myself. By the name God, 
I understand a substance infinite [eternal, immutable], 
independent, all-knowing, all-powerful, and by which I 
myself, and every other thing that exists, if any such there 
be, were created. But these properties are so great 
and excellent, that the more attentively I consider them 
the less I feel persuaded that the idea I have of them 
owes its origin to myself alone. And thus it is absolutely 
necessary to conclude, from all that I have before said, 
that God exists : for though the idea of substance be in my 
mind owing to this, that I myself am a substance, I should 
not, however, have the idea of an infinite substance, 
seeing I am a finite being, unless it were given me by 
some substance in reality infinite. 

And I must not imagme that I do not apprehend the 
infinite by a true idea, but only by the negation of the 
finite, in the same way that I comprehend repose and 
darkness by the negation of motion and light: since, on 
the contrary, I clearly perceive that there is more reality 
in the infinite substance than in the finite, and therefore 
that in some way I possess the perception (notion) of the 
infinite before that of the finite, that is, the perception 
of God before that of myself, for how could I know that 

Of God : That He Exists 105 

I doubt, desire, or that something is wanting to me, and 
that I am not wholly perfect, if I possessed no idea of 
a being more perfect than myself, by comparison of 
which I knew the deficiencies of my nature ? 

And it cannot be said this that idea of God is perhaps 
materially false, and consequently that it may have arisen 
from nothing [in other words, that it may exist in me 
from my imperfection], as I before said of the ideas of 
heat and cold, and the like: for, on the contrary, as this 
idea is very clear and distinct, and contains in itself more 
objective reality than any other, there can be no one of 
itself more true, or less open to the suspicion of falsity. 

The idea, I say, of a being supremely perfect, and 
infinite, is in the highest degree true; for although, per- 
haps, we may imagine that such a being does not exist, 
we cannot, nevertheless, suppose that his idea represents 
nothing real, as I have already said of the idea of cold. 
It is likewise clear and distinct in the highest degree, 
since whatever the mind clearly and distinctly conceives 
as real or true, and as implying any perfection, is con- 
tained entire in this idea. And this is true, nevertheless, 
although I do not comprehend the infinite, and although 
there may be in God an infinity of things that I cannot 
comprehend, nor perhaps even compass by thought in 
any way ; for it is of the nature of the infinite that it should 
not be comprehended by the finite ; and it is enough that 
I rightly understand this, and judge that all which I 
clearly perceive, and in which I know there is some per- 
fection, and perhaps also an infinity of properties of which 
I am ignorant, are formally or eminently in God, in order 
that the idea I have of him may become the most true, 
clear, and distinct of all the ideas in my mind. 

But perhaps I am sojo iething. more than I suppose 
myself to be, and it may be that all those perfections 
which I attribute to God, in sorhe way exist potentially in 
Hje, although they do not yet show themselves, and are 
not reduced to act. Indeed, I am already conscious that 
my knowledge is being increased [and perfected] by 
degrees ; and I see nothing to prevent it from thus gradu- 
ally increasing to infinity, nor any reason why, after such 
increase and perfection, I should not be able thereby to 

io6 Meditations 

acquire all the other perfections of the Divine nature; 
nor, in fine, why the power I possess of acquiring those 
perfections, if it really now exist in me, should not be 
V sufficient to produce the ideas of them. Yet, on looking 
more closely into the matter, I discover that this cannot 
be; for, in the first place, although it were true that my 
knowledge daily acquired new degrees of perfection, and 
although there were potentially in my nature much that 
was not as yet actually in it, still all these excellences make 
not the slightest approach to the idea I have of the Deity, 
in whom there is no perfection merely potentially [but 
• all actually] existent; for it is even an unmistakable 
token of imperfection in my knowledge, that it is aug- 
mented by degrees. Further, although my knowledge 
increase more and more, nevertheless I am not, therefore, 
^ induced to think that it will ever be actually infinite, since 
it can never reach that point beyond which it shall be 
incapable of furcher increase. But I conceive God as 
actually infinite, so that nothing can be added to his 
perfection. And, in fine, I readily perceive that the 
objective being of an idea cannot be produced by a being 
that is merely potentially existent, which, properly 
speaking, is nothing, but only by a being existing form- 
ally or actually. 

And, truly, I see nothing in all that I have now said 
which it is not easy for any one, who shall carefully con- 
sider it, to discern by the natural light ; but when I allow 
my attention in some degree to relax, the vision of my 
mind being obscured, and, as it were, blinded by the 
images of sensible objects, I do not readily remember the 
reason why the idea of a being more perfect than myself, 
must of necessity have proceeded from a being in reality 
more perfect. On this account I am here desirous to 
inquire further, whether I, who possess this idea of God, 
could exist supposing there were no God. And I ask, 
from whom could I, in that case, derive my existence? 
Perhaps from myself, or from my parents, or from some 
other causes less perfect than God; for anything more 
perfect, or even equal to God, cannot be thought or 
imagined. But if I [were independent of every other 
existence, and] were myself the author of my being, I 

Of God: That He Exists 107 

should doubt of nothing, I should desire nothing, and, 
in fine, no perfection would be awanting to me; for 
I should have bestowed upon myself every perfec- 
tion of which I possess the idea, and I should thus be 
God. And it must not be imagined that what is now 
wanting to me is perhaps of more difficult acquisition 
than that of which I am already possessed; for, on the 
contrary, it is quite manifest that it was a matter of much 
higher difficulty that I, a thinking being, should arise 
from nothing, than it would be for me to acquire the 
knowledge of many things of which I am ignorant, and 
which are merely the accidents of a thinking substance; 
and certainly, if I possessed of myself the greater per- 
fection of which I have now spoken [in other words, if 
I were the author of my own existence], I would not at 
least have denied to myself things that may be more 
easily obtained [as that infinite variety of knowledge of 
which I am at present destitute]. I could not, indeed, 
have denied to myself any property which I perceive is 
contained in the idea of God, because there is none of 
these that seems to me to be more difficult to make or 
acquire; and if there were any that should happen to be 
more difficult to acquire, they would certainly appear so 
to me (supposing that I myself were the source of the 
other things I possess), because I should discover in them 
a limit to my power. And though I were to suppose that 
I always was as I now am, I should not, on this ground, 
escape the force of these reasonings, since it would not 
follow, even on this supposition, that no author of my 
existence needed to be sought after. For the whole time 
of my life may be divided into an infinity of parts, each 
of which is in no way dependent on any other; and, 
accordingly, because I was in existence a short time ago, 
it does not follow that I must now exist, unless in this 
moment some cause create me anew, as it were, — that is, 
conserve me. In truth, it is perfectly clear and evident 
to all who will attentively consider the nature of duration 
that the conservation of a substance, in each moment of 
its duration, requires the same power and act that would 
be necessary to create it, supposing it were not yet in exist- 
ence; so that it is manifestly a dictate of the natural light 

o8 Meditations 

that conservation and creation differ merely in respect of 
our mode of thinking [and not in reahtyj. All that is 
here required, therefore, is that I interrogate myself to 
discover whether I possess any power by means of which 
I can bring it about that I, who now am, shall exist a 
moment afterwards: for, since I am merely a thinking 
thing (or since, at least, the precise question, in the mean- 
time, is only of that part of myself), if such a power resided 
in me^ I should, without doubt, be conscious of it; but 
I am conscious of no such power, and thereby I manifestly 
know that I am dependent upon some being different 
from myself. 

But perhaps the being upon whom I am dependent is 
not God, and I have been produced either by my parents, 
or by some causes less perfect than Deity. This cannot 
be: for, as I before said, it is perfectly evident that there 
must at least be as much reality in the cause as in its 
effect; and accordingly, since I am a thinking thing, 
and possess in myself an idea of God, whatever in the 
end be the cause of my existence, it must of necessity be 
admitted that it is likewise a thinking being, and that it 
possesses in itself the idea and all the perfections I attri- 
bute to Deity. Then it may again be inquired whether 
this cause owes its origin and existence to itself, or to 
some other cause. For if it be self-existent, it follows, 
from what I have before laid down, that this cause is 
God; for, since it possesses the perfection of self-existence, 
it must likewise, without doubt, have the power of actually 
possessing every perfection of which it has the idea, — in 
other words, all the perfections I conceive to belong to 
God. But if it owe its existence to another cause than 
itself, we demand again, for a similar reason, whether 
this second cause exists of itself or through some other, 
until, from stage to stage, we at length arrive at an 
ultimate cause, which will be God. And it is quite 
manifest that in this matter there can be no infinite 
regress of causes, seeing that the question raised respects 
not so much the cause which once produced me, as that 
by which I am at this present moment conserved. 

Nor can it be supposed that several causes concerned 
in my production, and that from one I received the idea 

Of God: That He Exists 109 

of one of the perfections I attribute to Deity, and from 
another the idea of some other, and thus that all those 
perfections are indeed found somewhere in the universe, 
but do not all exist together in a single being who is God; 
for, on the contrary, the unity, the simplicity or insepar- 
ability of all the properties of Deity, is one of the chief 
perfections I conceive him to possess; and the idea of 
this unity of all the perfections of Deity could certainly 
not be put into my mind by any cause from which I did 
not likewise receive the ideas of all the other perfections; 
for no power could enable me to embrace them in an 
inseparable unity, without at the same time giving me 
the knowledge of what they were [and of their existence 
in a particular mode]. 

Finally, with regard to my parents [from whom it 
appears I sprung], although all that I believed respecting 
them be true, it does not, nevertheless, follow that I am 
conserved by them, or even that I was produced by them, 
in so far as I am a thinking being. AUjiiaJt,^ thcLjuost, 
they c£>ntributed to my origin was'^the giving of certain 
dispositions (modifications) to the matter in which I have 
hitherto judged that I or my mind, which is what alone 
I now consider to be myself, is enclosed; and thus there 
can here be no difficulty with respect to them, and it is ab- 
solutely necessary to conclude from this alone that I am, 
and possess the idea of a being absolutely perfect, that is, 
of God, that his existence is most clearly demonstrated. 

There remains only the inquiry as to the way in which 
I received this idea from God; for I have not drawn it 
from the senses, nor is it even presented to me unexpec- 
tedly, as is usual with the ideas of sensible objects, when 
these are presented or appear to be presented to the 
external organs of the senses; it is not even a pure pro- 
duction or fiction of my mind, for it is not in my power 
to take from or add to it; and consequently there but 
remains the alternative that it is innate, in the same way 
as is the idea of myself. And, in truth, it is not to be 
wondered at that God, at my creation, implanted this 
idea in me, that it might serve, as it were, for the mark 
of the workman impressed on his work; and it is not also 
necessary that the mark should be something different 

no Meditations 

from the work itself; but considering only that God is my 
creator, it is highly probable that he in some way fashioned 
me after his own image and likeness, and that 1 perceive 
this likeness, in which is contained the idea of God, by 
the same faculty by which I apprehend myself,— in other 
words, when I make myself the object of reflection, I not 
only find that I am an incomplete [imperfect] and depen- 
dent being, and one who unceasingly aspires after some- 
thing better and greater than he is; but, at the same time, 
I am assured likewise that he upon whom I am dependent 
possesses in himself all the goods after which I aspire 
[and the ideas of which I find in my mind], and that not 
merely indefinitely and potentially, but infinitely and 
actually, and that he is thus God. And the whole force 
of the argument of which I have here availed myself to 
establish the existence of God, consists in this, that I 
perceive I could not possibly be of such a nature as I am, 
and yet have in my mind the idea of a God, if God did not 
in reality exist, — this same God, I say, whose idea is in 
my mind — that is, a being who possesses all those lofty 
perfections, of which the mind may have some slight 
conception, without, however, being able fully to com- 
prehend them,— and who is wholly superior to all defect 
[and has nothing that marks imperfection] : whence it is 
sufficiently manifest that he cannot be a deceiver, since 
it is a dictate of the natural light that all fraud and 
deception spring from some defect. 

But before I examine this with more attention, and 
pass on to the consideration of other truths that may be 
evolved out of it, I think it proper to remain here for some 
time in the contemplation of God himself — that I may 
ponder at leisure his marvellous attributes — and behold, 
admire, and adore the beauty of this light so unspeakably 
great, as far, at least, as the strength of my mind, which 
is to some degree dazzled by the sight, will permit. For 
just as we learn by faith that the supreme felicity of 
another Hfe consists in the contemplation of the Divine 
majesty alone, so even now we learn from experience that 
a like meditation, though incomparably less perfect, is the 
source of the highest satisfaction of which we are sus- 
ceptible in this life. 



I HAVE been habituated these bygone days to detach my 
mind from the senses, and I have accurately observed 
that there is exceedingly little which is known with 
certainty respecting corporeal objects, — that we know 
much more of the human mind, and still more of God 
himself. I am thus able now without difficulty to abstract 
my mind from the contemplation of [sensible or] imagin- 
able objects, and apply it to those which, as disengaged 
from all matter, are purely intelligible. And certainly 
the idea I have of the human mind in so far as it is a 
thinking thing, and not extended in length, breadth, and 
depth, and participating in none of the properties of body, 
is incomparably more distinct than the idea of any cor- 
poreal object; and when I consider that I doubt, in other 
words, that I am an incomplete and dependent being, 
the idea of a complete and independent being, that is to 
say of God, occurs to my mind with so much clearness 
and distinctness, — and from the fact alone that this idea 
is found in me, or that I who possess it exist, the conclu- 
sions that God exists, and that my own existence, each 
moment of its continuance, is absolutely dependent upon 
him, are so manifest, — as to lead me to believe it impos- 
sible that the human mind can know anything with more 
clearness and certitude. And now I seem to discover 
a path that will conduct us from the contemplation of the 
true God, in whom are contained all the treasures of 
science and wisdom, to the knowledge of the other things 
in the universe. 

For, in the first place, I discover that it is impossible 
for him ever to deceive me, for in all fraud and deceit 
there is a certain imperfection: and although it may seem 
that the ability to deceive is a mark of subtlety or power, 
yet the will testifies without doubt of malice and weak- 


I 12 


ness; and such, accordingly, can be found in God. In 
the next place, I am conscious that I possess a certain 
faculty of judging [or discerning truth from error], which 
I doubtless received from God, along with whatever else 
is mine; and since it is impossible that he should will to 
deceive me, it is likewise certain that he has not given 
me a faculty that will ever lead me into error, provided 
I use it aright. 

And there would remain no doubt on this head, did it 
not seem to follow from this, that I can never therefore be 
deceived ; for if all I possess be from God, and if he planted 
in me no faculty that is deceitful, it seems to follow that 
I can never fall into error. Accordingly, it is true that 
when I think only of God (when I look upon myself as 
coming from God, Fr.), and turn wholly to him, I discover 
[in myself] no cause of error or falsity: but immediately 
thereafter, recurring to myself, experience assures me that 
I am nevertheless subject to innumerable errors. When 
I come to inquire into the cause of these, I observe that 
there is not only present to my consciousness a real and 
positive idea of God, or of a being supremely perfect, but 
also, so to speak, a certain negative idea of nothing, — in 
other words, of that which is at an infinite distance from 
every sort of perfection, and that I am, as it were, a mean 
between God and nothing, or placed in such a way between 
absolute existence and non-existence, that there is in 
truth nothing in me to lead me into error, in so far as an 
absolute being is my creator; but that, on the other hand, 
as I thus likewise participate in some degree of nothing or 
of non-being, in other words, as I am not myself the 
supreme Being, and as I am wanting in many perfections, 
it is not surprising I should fall into error. And I hence 
discern that error, so far as error is not something real, 
which depends for its existence on God, but is simply 
defect; and therefore that, in order to fall into it, it is not 
necessary God should have given me a faculty expressly 
for this end, but that my being deceived arises from the 
circumstance that the power which God has given me of 
discerning truth from error is not infinite. 

Nevertheless this is not yet quite satisfactory; for error 
is not a pure negation [in other words, it is not the simple 

Of Truth and Error 1 1 3 

deficiency or want of some knowledge which is not due], 
but the privation or want of some knowledge which it 
would seem I ought to possess. But, on considering the 
nature of God, it seems impossible that he should have 
planted in his creature any faculty not perfect in its kind, 
that is, wanting in some perfection due to it: for if it be 
true, that in proportion to the skill of the maker the per- 
fection of his work is greater, what thing can have been 
produced by the supreme Creator of the universe that is 
not absolutely perfect in all its parts? And assuredly 
there is no doubt that God could have created me such as 
that I should never be deceived; it is certain, likewise, 
that he always wills what is best: is it better, then, that 
I should be capable of being deceived than that I should 

Considering this more attentively, the first thing that 
occurs to me is the reflection that I must not be surprised 
if I am not always capable of comprehending the reasons 
why God acts as he does; nor must I doubt of his existence 
because I find, perhaps, that there are several other 
things, besides the present respecting which I understand 
neither why nor how they were created by him; for, 
knowing already that my nature is extremely weak and 
limited, and that the nature of God, on the other hand, 
is immense, incomprehensible, and infinite, I have no 
longer any difficulty in discerning that there is an infinity 
of things in his power whose causes transcend the grasp 
of my mind: and this consideration alone is sufficient to 
convince me, that the whole class of final causes is of no 
avail in physical [or natural] things; for it appears to me 
that I cannot, without exposing myself to the charge of 
temerity, seek to discover the [impenetrable] ends of 

It further occurs to me that we must not consider only 
one creature apart'from the others, if we wish to determine 
the perfection of the works of Deity, but generally all his 
creatures together; for the same object that might per- 
haps, with some show of reason, be deemed highly imper- 
fect if it were alone in the world, may for all that be the 
most perfect possible, considered as forming part of the 
whole universe: and although, as it was my purpose to 


1 14 Meditations 

doubt of everything, I only as yet know with certainly 
my own existence and that of God, nevertheless, after 
having remarked the infinite power of Deity, I^ cannot 
deny that he may have produced many other objects, or 
at least that he is able to produce them, so that I may 
occupy a place in the relation of a part to the great whole 
of his creatures. 

Whereupon, regarding myself more closely, and con- 
sidering what my errors are (which alone testify to the i 
existence of imperfection in me), I observe that these 
depend on the concurrence of two causes, viz., the faculty 
of cognition which I possess, and that of election or the 
power of free choice, — in other words, the understanding i 
and the will. For by the understanding alone, I [neither 
affirm nor deny anything, but] merely apprehend {per- 
cipio) the ideas regarding which I may form a judgment; 
nor is any error, properly so called, found in it thus accur- 
ately taken. And although there are perhaps innumer- 
able objects in the world of which I have no idea in my 
understanding, it cannot, on that account, be said that I 
am deprived of those ideas [as of something that is due 
to my nature], but simply that I do not possess them, 
because, in truth, there is no ground to prove that Deity 
ought to have endowed me with a larger faculty of cogni- 
tion than he has actually bestowed upon me; and how- 
ever skilful a workman I suppose him to be, I have no 
reason, on that account, to think that it was obligatory 
on him to give to each of his works all the perfections 
he is able to bestow upon some. Nor, moreover, can I 
complain that God has not given me freedom of choice, 
or a will sufficiently ample and perfect, since, in truth, I 
am conscious of will so ample and extended as to be 
superior to all limits. And what appears to me here to 
be highly remarkable is that, of all the other properties I 
possess, there is none so great and perfect as that I do not 
clearly discern it could be still greater and more perfect. 
For, to take an example, if I consider the faculty of under- 
standing which I possess, I find that it is of very small 
extent, and greatly limited, and at the same time I form 
the idea of another faculty of the same nature, much 
more ample and even infinite ; and seeing that I can frame 

Of Truth and Error 1 15 

the idea of it, I discover, from this circumstance alone, 
that it pertains to the nature of God. In the same way, 
if I examine the faculty of memory or imagination, or any 
other faculty I possess, I find none that is not small and 
circumscribed, and in God immense [and infinite]. It is 
the faculty of will only, or freedom of choice, which I 
experience to be so great that I am unable to conceive 
the idea of another that shall be more ample and ex- 
tended; so that it is chiefly my will which leads me to 
discern that I bear a certain image and similitude of 
Deity. For although the faculty of will is incomparably 
greater in God than in myself, as well in respect of the 
knowledge and power that are conjoined with it, and that 
render it stronger and more efficacious, as in respect of 
the object, since in him it extends to a greater number of 
things, it does not, nevertheless, appear to me greater, 
considered in itself formally and precisely: for the power 
of will consists only in this, that we are able to do or not 
to do the same thing (that is, to afhrm or deny, to pursue 
or shun it), or rather in this alone, that in affirming or 
denying, pursuing or shunning, what is proposed to us by 
the understanding, we so act that we are not conscious of 
being determined to a particular action by any external 
force. For, to the possession of freedom, it is not neces- 
sary that I be alike indifferent towards each of two con- 
traries; but, on the contrary, the more I am inclined 
towards the one, whether because I clearly know that in 
it there is the reason of truth and goodness, or because 
God thus internally disposes my thought, the more freely 
do I choose and embrace it; and assuredly divine grace 
and natural knowledge, very far from diminishing liberty, 
rather augment and fortify it. But the indifference of 
which I am conscious when I am not impelled to one side 
rather than to another for want of a reason, is the lowest 
grade of liberty, and manifests defect or negation of 
knowledge rather than perfection, of will; for if I always 
clearly knew what was true and good, I should never have 
any difficulty in determining what judgment I ought to 
come to, and what choice I ought to make, and I should 
thus be entirely free without ever being indifferent. 
From all this I discover, however, that neither the 

1 1 6 Meditations 

power of willing, which I have received from God, is of 
itself the source of my errors, for it is exceedingly ample 
and perfect in its kind; nor even the power of under- 
standing, for as I conceive no object unless by means of 
the faculty that God bestowed upon me, all that I con- 
ceive is doubtless rightly conceived by me, and it is 
impossible for me to be deceived in it. 

Whence, then, spring my errors? They arise from this 
cause alone, that I do not restrain the will, which is of 
much wider range than the understanding, within the 
same limits, but extend it even to things I do not under- 
stand, and as the will is of itself indifferent to such, it 
readily falls into error and sin by choosing the false in 
room of the true, and evil instead of good. 

For example, when I lately considered whether aught 
really existed in the world, and found that because I con- 
sidered this question, it very manifestly followed that I 
myself existed, I could not but judge that what I so 
clearly conceived was true, not that I was forced to this 
judgment by any external cause, but simply because 
great clearness of the understanding was succeeded by 
strong inclination in the will; and I believed this the 
more freely and spontaneously in proportion as I was 
less indifferent with respect to it. But now I not only 
know that J exist, in so far as I am a thinking being, but 
there is likewise presented to my mind a certain idea of 
corporeal nature; hence I am in doubt as to whether the 
thinking nature which is in me, or rather which I myself 
am, is different from that corporeal nature, or whether 
both are merely one and the same thing, and I here suppose 
that I am as yet ignorant of any reason that would deter- 
mine me to adopt the one belief in preference to the other: 
whence it happens that it is a matter of perfect indif- 
ference to me which of the two suppositions I affirm or 
deny, or whether I form any judgment at all in the matter. 

This indifference, moreover, extends not only to things 
of which the understanding has no knowledge at all, but 
in general also to all those which it does not discover with 
perfect clearness at the moment the will is deliberating 
upon them; for, however probable the conjectures may 
be that dispose me to form a judgment in a particular 

Of Truth and Error 1 1 7 

matter, the simple knowledge that these are merely con- 
jectures, and not certain and indubitable reasons, is 
sufficient to lead me to form one that is directly the 
opposite. Of this I lately had abundant experience, 
when I laid aside as false all that I had before held for 
true, on the single ground that I could in some degree 
doubt of it. But if I abstain from judging of a thing 
when I do not conceive it with sufficient clearness and 
distinctness, it is plain that I act rightly, and am not 
deceived; but if I resolve to deny or affirm, I then do not 
make a right use of my free will; and if I affirm what is 
false, it is evident that I am deceived: moreover, even 
although I judge according to truth, I stumble upon it by 
chance, and do not therefore escape the imputation of a 
i wrong use of my freedom ; for it is a dictate of the natural 
light, that the knowledge of the understanding ought 
always to precede the determination of the will. 

And it is this wrong use of freedom of the will in which 
is found the privation that constitutes the form of error. 
I Privation, I say, is found in the act, in so far as it pro- 
ceeds from myself, but it does not exist in the faculty 
which I received from God, nor even in the act, in so far 
ias it depends on him; for I have assuredly no reason to 
I complain that God has not given me a greater power of 
intelligence or more perfect natural light than he has 
actually bestowed, since it is of the nature of a finite 
understanding not to comprehend many things, and of 
the nature of a created understanding to be finite; on 
the contrary, I have every reason to render thanks to 
God, who owed me nothing, for having given me all the 
perfections I possess, and I should be far from thinking 
that he has unjustly deprived me of, or kept back, the 
other perfections which he has not bestowed upon me. 

I have no reason, moreover, to complain because he has 
given me a will more ample than my understanding, 
since, as the will consists only of a single element, and that 
indivisible, it would appear that this faculty is of such a 
nature that nothing could be taken from it [without 
destroying it]; and certainly, the more extensive it is, 
the more cause I have to thank the goodness of him who 
bestowed it upon me. 

1 1 8 Meditations 

And, finally, I ought not also to complain that God 
concurs with me in forming the acts of this will, or the 
judgments in which I am deceived, because those acts are 
wholly true and good, in so far as they depend on God; 
and the ability to form them is a higher degree of perfec- 
tion in my nature than the want of it would be. With 
regard to privation, in which alone consists the formal 
reason of error and sin, this does not require the con- 
currence of Deity, because it is not a thing [or existence], 
and if it be referred to God as to its cause, it ought not 
to be called privation, but negation [according to the 
signification of these words in the schools]. For in truth 
it is no imperfection in Deity that he has accorded to me 
the power of giving or withholding my assent from cer- 
tain things of which he has not put a clear and distinct 
knowledge in my understanding; but it is doubtless an 
imperfection in me that I do not use my freedom aright, 
and readily give my judgment on matters which I only 
obscurely and confusedly conceive. 

I perceive, nevertheless, that it was easy for Deity so 
to have constituted me as that I should never be deceived, 
although I still remained free and possessed of a limited 
knowledge, viz., by implanting in my understanding a 
clear and distinct knowledge of all the objects respecting 
which I should ever have to deliberate; or simply by so 
deeply engraving on my memory the resolution to judge 
of nothing without previously possessing a clear and 
distinct conception of it, that I should never forget it. 
And I easily understand that, in so far as I consider 
myself as a single whole, without reference to any other 
being in the universe, I should have been much more 
perfect than I now am, had Deity created me superior to 
error; but I cannot therefore deny that it is not somehow 
a greater perfection in the universe, that certain of its 
parts are not exempt from defect, as others are, than if- 
they were all perfectly alike. 

And I have no right to complain because God, who 
placed me in the world, was not willing that I should 
sustain that character which of all others is the chief and 
most perfect; I have even good reason to remain satisfied 
on the ground that, if he has not given me the perfection 

Of Truth and Error 1 1 9 

of being superior to error by the first means I have pointed 
out above, which depends on a clear and evident know- 
ledge of all the matters regarding which I can deliberate, 
he has at least left in my power the other means, which is, 
firmly to retain the resolution never to judge where the 
truth is not clearly known to me: for, although I am con- 
scious of the weakness of not being able to keep my mind 
continually fixed on the same thought, I can nevertheless, 
by attentive and oft-repeated meditation, impress it so 
strongly on my memory that I shall never fail to recollect 
it as often as I require it, and I can acquire in this way the 
habitude of not erring; and since it is in being superior 
to error that the highest and chief perfection of man con- 
sists, I deem that I have not gained little by this day's 
meditation, in having discovered the source of error and 

And certainly t;his can be no other than what I have 
now explained: /for as often as I so restrain my will 
within the limits of my knowledge, that it forms no judg- 
ment except regarding objects which are clearly and 
distinctly represented to it by the understanding, I can 
never be deceived ; because every clear and distinct con- 
ception Ts doubtless something, and as such cannot owe 
its origin to nothing, but must of necessity have God for 
its author — God, I say, who, as supremely perfect, cannot, 
without a contradiction, be the cause of any error; and 
consequently it is necessary to conclude that every such 
conception [or judgment] is true. Nor have I merely 
learned to-day what I must avoid to escape error, but 
also what I must do to arrive at the knowledge of truth; 
for I will assuredly reach truth if I only fix my attention 
sufficiently on all the things I conceive perfectly, and 
separate these from others which I conceive more con- 
fusedly and obscurely: to which for the future I shall 
give diligent heed. / 



Several other questions remain for consideration respect- 
ing the attributes of God and my own nature or mind. I 
will, however, on some other occasion perhaps resume the 
investigation of these. Meanwhile, as I have discovered 
what must be done, and what avoided to arrive at the 
knowledge of truth, what I have chiefly to do is to essay 
to emerge from the state of doubt in which I have for 
some time been, and to discover whether anything can 
be known with certainty regarding material objects. But 
before considering whether such objects as I conceive 
exist without me, I must examine their ideas in so far as 
these are to be found in my consciousness, and discover 
which of them are distinct and which confused. 

In the first place, I distinctly imagine that quantity 
which t he philosophers commonly call continuous, or the__ 
extension m leng th, breadth, and dept h that is in this 
quantity,"or'rather in the object to which it is attributedT" 
Further, I can enumerate in it many diverse parts, and 
attribute to each of these all sorts of sizes, figures, situa- 
tions, and local motions; and, in fine, I can assign to each 
of these motions all degrees of duration. And I not only 
distinctly know these things when I thus consider them 
in general; but besides, by a little attention, I discover 
innumerable particulars respecting figures, numbers, 
motion, and the like, which are so evidently true, and so 
accordant with my nature, that when I now discover them 
I do not so much appear to learn anything new, as to call 
to remembrance what I before knew, or for the first time 
to remark what was before in my mind, but to which I had 
not hitherto directed my attention. And what I here find 
of most importance is, that I discover in my mind in- 
numerable ideas of certain objects, which cannot be 


The Essence of Material Things 1 2 1 

esteemed pure negations, although perhaps they possess 
no reality beyond my thought, and which are not framed 
by me though it may be in my power to think, or not to 
think them, but possess true and immutable natures of 
their own. As, for example, when I imagine a triangle, 
although there is not perhaps and never was in any place 
in the universe apart from my thought one such figure, 
it remains true nevertheless that this figure possesses a 
certain determinate nature, form, or essence, which is 
immutable and eternal, and not framed by me, nor in any 
degree dependent on my thought; as appears from the 
circumstance, that diverse properties of the triangle may 
be demonstrated, viz., that its three angles are equal to 
two right, that its greatest side is subtended by its greatest 
angle, and the like, which, whether I will or not, I now 
clearly discern to belong to it, although before I did not 
at all think of them, when, for the first time, I imagined 
a triangle, and which accordingly cannot be said to have 
been invented by me. Nor is it a valid objection to 
allege, that perhaps this idea of a triangle came into my 
mind by the medium of the senses, through my having 
seen bodies of a triangular figure; for I am able to form 
in thought an innumerable variety of figures with regard 
to which it cannot be supposed that they were ever 
objects of sense, and I can nevertheless demonstrate 
diverse properties of their nature no less than of the 
triangle, all of which are assuredly true since I clearly 
conceive them; and they are therefore something, and 
not mere negations; for it is highly evident that all that 
is true is something [truth being identical with existence^; 
and I have already fully shown the truth of the principle, 
that whatever is clearly and distinctly known is true. 
And although this had not been demonstrated, yet the 
nature of my mind is such as to compel me to assent to 
what I clearly conceive while I so conceive it; and I 
recollect that even when I still strongly adhered to the 
objects of sense, I reckoned among the number of the 
most certain truths those I clearly conceived relating 
to figures, numbers, and other matters that pertain to 
arithmetic and geometry, and in general to the pure 

122 Meditations 

But now if because I can draw from my thought the 
idea of an object, it follows that all I clearly and distinctly 
apprehend to pertain to this object, does in truth belong 
to it, may I not from this derive an argument for the exist- 
ence of God? It is certain that I no less find the idea of 
a God in my consciousness, that is, the idea of a being 
supremely perfect, than that of any figure or number 
whatever: and I know with not less clearness and dis- 
tinctness that an [actual and] eternal existence pertains to 
his nature than that all which is demonstrable of any figure 
or number really belongs to the nature of that figure or 
number; and, therefore, although all the conclusions of 
the preceding Meditations were false, the existence of 
God would pass with me for a truth at least as certain as 
I ever judged any truth of mathematics to be, although 
indeed such a doctrine may at first sight appear to contain 
more sophistry than truth. For, as I have been accus- 
tomed in every other matter to distinguish between 
existence and essence, I easily believe that the existence 
can be separated from the ess ence of G od, and that thus 
God may be conceived as'^not actually' existing. But, 
nevertheless, when I think of it more attentively, it 
appears that the existence can no more be separated from 
the essence of God than the idea of a mountain from that 
of a valley, or the equality of its three angles to two right 
angles, from the essence of a [rectilineal] triangle; so that 
it is not less impossible to conceive a God, that is, a being 
supremely perfect, to whom existence is awanting, or 
who is devoid of a certain perfection, than to conceive a 
mountain without a valley. 

But though, in truth, I cannot conceive a God unless 
as existing, any more than I can a mountain without a 
valley, yet, just as it does not follow that there is any 
mountain in the world merely because I conceive a moun- 
tain with a valley, so likewise, though I conceive God as 
existing, it does not seem to follow on that account that 
God exists; for my thought imposes no necessity on 
things; and as I may imagine a winged horse, though 
there be none such, so I could perhaps attribute existence 
to God, though no God existed. But the cases are not 
analogous, and a fallacy lurks under the semblance of this 

The Essence of Material Things 123 

objection: for because I cannot conceive a mountain 
without a valley, it does not follow that there is any 
mountain or valley in existence, but simply that the 
mountain or valley, whether they do or do not exist, are 
inseparable from each other; whereas, on the other hand, 
because I cannot conceive God unless as existing, it 
follows that existence is inseparable from him, and there- 
fore that he really exists: not that this is brought about 
by my thought, or that it imposes any necessity on 
things, but, on the contrary, the necessity which lies ii^ 
the thing itself, that is, the necessity of the existence of, 
God, determines me to think in this way, for it is not ii ' 
my power to conceive a God without existence, that is [ 
a being supremely perfect, and yet devoid of an absolute \ 
perfection, as I am free to imagine a horse with or without, 

Nor must it be alleged here as an objection, that it is in 
truth necessary to admit that God exists, after having 
supposed him to possess all perfections, since existence is 
one of them, but that my original supposition was not 
necessary; just as it is not necessary to think that all 
quadrilateral figures can be inscribed in the circle, since, 
if I supposed this, I should be constrained to admit that 
the rhombus, being a figure of four sides, can be therein 
inscribed, which, however, is manifestly false. This 
objection is, I say, incompetent; for although it may not 
be necessary that I shall at any time entertain the notion 
of Deity, yet each time I happen to think of a first and 
sovereign being, and to draw, so to speak, the idea of him 
from the store-house of the mind, I am necessitated to 
attribute to him all kinds of perfections, though I may not 
then enumerate them all, nor think of each of them in 
particular. And this necessity is sufficient, as soon as I 
discover that existence is a perfection, to cause me to infer 
the existence of this first and sovereign being; just as it is 
not necessary that I should ever imagine any triangle, 
but whenever I am desirous of considering a rectilineal 
figure composed of only three angles, it is absolutely 
necessary to attribute those properties to it from which 
it is correctly inferred that its three angles are not greater 
than two right angles, although perhaps I may not then 

1 24 Meditations 

advert to this relation in particular. But when I con- 
sider what figures are capable of being inscribed in the 
circle, it is by no means necessary to hold that all quadri- 
lateral figures are of this number; on the contrary, I 
cannot even imagine such to be the case, so long as I 
shall be unwilling to accept in thought aught that I do 
not clearly and distinctly conceive: and consequently 
there is a vast difference between false suppositions, as 
is the one in question, and the true ideas that were bom 
with me, the first and chief of which is the idea of God. 
For indeed I discern on many grounds that this idea is not 
factitious, depending simply on my thought, but that it 
is the representation of a true and immutable nature: in 
the first place, because I can conceive no other being, 
except God, to whose essence existence [necessarily] 
pertains; in the second, because it is impossible to con- 
ceive two or more gods of this kind; and it being supposed 
that one such God exists, I clearly see that he must have 
existed from all eternity, and will exist to all eternity; 
and finally, because I apprehend many other properties in 
God, none of which I can either diminish or change. 

But, indeed, whatever mode of probation I in the end 
adopt, it always returns to this, that it is only the things 
Ijclearly ^nd distinctl; ^Mconceive which have the power of 
completely persuadmg me. ^And although, of the objects 
I^'conceive in this manner, some, indeed, are obvious to 
every one, while others are only discovered after close 
and careful investigation; nevertheless, after they are 
once discovered, the latter are not esteemed less certain 
than the former. Thus, for example, to take the case 
of a right-angled triangle, although it is not so manifest 
at first that the square of the base is equal to the squares 
of the other two sides, as that the base is opposite to the 
greatest angle; nevertheless, after it is once apprehended, 
we are as firmly persuaded of the truth of the former as 
of the latter. And, with respect to God, if I were not 
preoccupied by prejudices, and my thoughts beset on 
all sides by the continual presence of the images of sensible 
objects, I should know nothing sooner or more easily 
than the fact of his being. For is there any truth more 
clear than the existence of a Supreme Being, or of God, 

The Essence of Material Things 125 

seeing it is to his essence alone that [necessary and eternal] 
existence pertains? And although the right conception 
of this truth has cost me much close thinking, neverthe- 
less at present I feel not only as assured of it as of what 
I deem most certain, but I remark further that the certi- 
tude of all other truths is so absolutely dependent on it, 
that without this knowledge it is impossible ever to know 
anything perfectly. 

For although I am of such a nature as to be unable, 
while I possess a very clear and distinct apprehension of 
a matter, to resist the conviction of its truth, yet because 
my constitution is also such as to incapacitate me from 
keeping my mind continually fixed on the same object, 
and as I frequently recollect a past judgment without at 
the same time being able to recall the grounds of it, it 
may happen meanwhile that other reasons are presented 
to me which would readily cause me to change my opinion, 
if I did not know that God existed; and thus I should 
possess no true and certain knowledge, but merely vague 
and vacillating opinions. Thus, for example, when I 
consider the nature of the [rectilineal] triangle, it most 
clearly appears to me, who have been instructed in the 
principles of geometry, that its three angles are equal 
to two right angles, and I find it impossible to believe 
otherwise, while I apply my mind to the demonstration; 
but as soon as I cease from attending to the process of 
proof, although I still remember that I had a clear com- 
prehension of it, yet I may readily come to doubt of the 
truth demonstrated, if I do not know that there is a God : 
for I may persuade myself that I have been so constituted 
by nature as to be sometimes deceived, even in matters 
which I think I apprehend with the greatest evidence and 
certitude, especially when I recollect that I frequently 
considered many things to be true and certain which other 
reasons afterwards constrained me to reckon as wholly 

But after I have discovered that God exists, seeing I 
also at the same time observed that all things depend on 
him, and that he is no deceiver, and thence inferred that 
all which I clearly and distinctly perceive is of necessity 
true: although I no longer attend to the grounds of a 

126 Meditations 

judgment, no opposite reason can be alleged sufficient to 
lead me to doubt of its truth, provided only Ixein&inbeJ* 
that I once possessed a clear and distinct comprehension 
of it. My knowledge of it thus becomes true and certain. 
And this same knowledge extends likewise to whatever 
I remember to have formerly demonstrated, as the truths 
of geometry and the like: for what can be alleged against 
them to lead me to doubt of them?) Will it be that my 
nature is such that 1 may be frequently deceived ? But 
I already know that I cannot be deceived in judgments 
of the grounds of which I possess a clear knowledge. Will 
it be that I formerly deemed things to be true and certain 
which I afterwards discovered to be false.? But I had 
no clear and distinct knowledge of any of those things, 
and, being as yet ignorant of the rule by which I am 
assured of the truth of a judgment, I was led to give my 
assent to them on grounds which I afterwards discovered 
were less strong than at the time I imagined them to be. 
What further objection, then, is there? Will it be said 
that perhaps I am dreaming (an objection I lately myself 
raised), or that all the thoughts of which I am now 
conscious have no more truth than the reveries of my 
dreams? But although, in truth, I should be dreaming, 
the rule still holds that all which is clearly presented to 
my intellect is indisputably true. 

And thus I very clearly see that the certitude and truth 
of all science depends on the knowledge alone of the true 
God, insomuch that, before I knew him, I could have 
no perfect knowledge of any other thing. And now that 
I know him, I possess the means of acquiring a per- 
fect knowledge respecting innumerable matters, as well 
relative to God himself and other intellectual objects as 
to corporeal nature, in so far as it is the object of pure 
mathematics [which do not consider whether it exists 
or not]. 



There now only remains the inquiry as to whether 
material things exist. With regard to this question, I 
at least know with certainty that such things may exist, 
in as far as they constitute the object of the pure mathe- 
matics, since, regarding them in this aspect, I can con- 
ceive them clearly and distinctly. For there can be no 
doubt that God possesses the power of producing all the 
objects I am able distinctly to conceive, and I never 
considered anything impossible to him, unless when I 
experienced a contradiction in the attempt to conceive 
it aright. Further, the faculty of imagination which I 
possess, and of which I am conscious that I make use 
when I apply myself to the consideration of material 
things, is sufficient to persuade me of their existence: 
for, when I a tten_t i vely consi der what in^^gina ^n is^ I 
find that it is si mp l y a c ertain application of the cognitive^ 

iaamy^lfacultas cognoscitivayto a body which is imm^di=- 
atelypresent to it, and which therefore exists. ^ 

IShd to render this quite clear, I remark, in the first 
place, the difference that subsists between imagination 
and pure intellection [or conception]. For example, 
when I imagine a triangle I not only conceive (intelligo) 
that it is a figure comprehended by three lines, but at 
the same time also I look upon (intueor) these three lines 
as present by the power and internal application of my 
mind (acie mentis), and this is what I call imagining. 
But if I desire to think of a chiliogon, I indeed rightly 
conceive that it is a figure composed of a thousand sides, 
as easily as I conceive that a triangle is a figure composed 
of only three sides; but I cannot imagine the thousand 
sides of a chiliogon as I do the three sides of a triangle, 
nor, so to speak, view them as present [with the eyes of 


128 Meditations 

my mind]. And although, in accordance with the habit 
I have of always imagining something when I think of 
corporeal things, it may happen that, in conceiving a 
chiliogon, I confusedly represent some figure to myself, 
yet it is quite evident that this is not a chiliogon, since it 
in no wise differs from that which I would represent to 
myself, if I were to think of a myriogon, or any other 
figure of many sides; nor would this representation be 
of any use in discovering and unfolding the properties 
that constitute the difference between a chiliogon and 
other polygons. But if the question turns on a pentagon, 
it is quite true that I can conceive its figure, as well as 
that of a chiliogon, without the aid of imagination; but 
I can likewise imagine it by applying the attention of my 
mind to its five sides, and at the same time to the area 
which they contain. Thus I observe that a special effort 
of mind is necessary to the act of imagination, which is 
not required to conceiving or understanding (ad intelligent 
dum); and this special exertion of mind clearly shows the 
difference between imagination and pure intellection 
(imaginatio et intellectio pura). I remark, besides, that 
this power of imagination which I possess, in as far as it 
differs from the power of conceiving, is in no way necessary 
to my [nature or] essence, that is, to the essence of my 
mind; for although I did not possess it, I should still 
remain the same that I now am, from which it seems 
^ we may conclude that it depends on something different 
•0 from the mind. And I easily understand that, if somes 
" body exists, with which my mind is so conjoined and \ 
united as to be able, as it were, to consider it when it \ 
chooses, it may thus imagine corporeal objects; so that ■-, 
this mode of thinking differs from pure int ellection onlyj n ; 
this respect, jhat the mind in conc eiving turns in some way 
Uj^njtseffJa Hd^nH some one^ the ideas iFpossesse s 
within Itse lf ;~ b ut in ima gining it turns tow ards the body , 
and con te mplates in it some obTect conformed to the ide a 
which 11 either ot itself conceived or apprehended by 
s^ise^ 1 easily understand, I say, that imaginationlnay 
be thus formed, if it is true that there are bodies ; and 
because I find no other obvious modr^ot explaining it, y 
I thence, with probability, conjecture that they exist. 

Existence of Material Things 1 29 

but J9nl5^..j«ith .probabilityj^ and although I carefully 
examine all things, nevertheless I do not find that, from 
the distinct idea of corporeal nature I have in my imagi- 
nation, I can necessarily infer the existence of any body. 
But I am accustomed to imagine many other objects 
besides that corporeal nature which is the object of the 
pure mathematics, as, for example, colours, sounds, 
tastes, pain, and the like, although with less distinctness; 
and, inasmuch as I perceive these objects much better 
by the senses, through the medium of which and of 
memory, they seem to have reached the imagination, 
I believe that, in order the more advantageously to 
examine them, it is proper I should at the same time 
examine what sense-perception is, and inquire whether 
from those ideas that are apprehended by this mode of 
thinking (consciousness), I cannot obtain a certain proof 
of the existence of corporeal objects. 
y And, in the first place, I will recall to my mind the 
\things I have hitherto held as true, because perceived by 
Jthe senses, and the foundations upon which my belief 
j in their truth rested ; I will, in the second place, examine 
the reasons that afterwards constrained me to doubt of 
them; and, finally, I will consider what of them I ought 
how to believe. _ 

-firstly, then, I perceived that I had a head, hands, fee?7^ 
and other members composing that body which I con- :l 
sidered as part, or perhaps even as the whole, of myself. 
I p erce i ved further, that that body was placed among ' 
many "others, by which it was capable of being affected 
in diverse ways, both beneficial and hurtful; and what 
was beneficial I remarked by a certain sensation of plea- 
sure, and what was hurtful by a sensation of pain. And, 
besides this pleasure and pain, I was likewise conscious 
of hunger, thirst, and other appetites, as well as certain 
corporeal inclinations towards joy, sadness, anger, and 
similar passions. And, out of myself, besides the exten- 
sion, figure, and motions of bodies, I likewise perceived 
in them hardness, heat, and the other tactile qualities, 
and, in addition, light, colours, odours, tastes, and sounds, 
the variety of which gave me the means of distinguishing 
the sky, the earth, the sea, and generally all the other 



bodies, from one another. And certainly, considering 
the ideas of all these qualities, which were presented to my 
mind, and which alone I properly and.imiaediatdyger- 
.' ceived, it was not without reason that I thought I per- i 
ceived certain objects wholly different from my thought, 
namely, bodies from which those ideas proceeded; for I 
was conscious that the ideas were presented to me without 
my consent being required, so that I could not perceive 
any object, however desirous I might be, unless it were 
present to the organ of sense; and it was wholly out of 
my power not to perceive it when it was thus present. 
And because the ideas I perceived by the senses were 
much more lively and clear, and even, in their own way, 
more distinct than any of those I could of myself frame 
by meditation, or which I found impressed on my memory, 
it seemed that they could not have proceeded from myself, 
and must therefore have been caused in me by some other 
objects: and as of those objects I had no knowledge 
beyond what the ideas themselves gave me, nothing was 
so likely to occur to my mind as the supposition that 
the objects were similar to the ideas which they caused. 
And because I recollected also that I had formerly trusted 
to the senses, rather than to reason, and that the ideas 
wRfc h I niybel flbfmea"'w€re not so clear as those I per- 
ceived by sense, and that they were even for the most 
part composed of parts of the latter, I was readily per- 
suaded that I had no idea in my intellect which had 
not formerly passed through the senses. Nor was I alto- 
gether wrong in likewise believing that that body which, 
by a special right, I called my own, pertained to me more 
properly and strictly than any of the others; for in truth, 
I could never be separated from it as from other bodies: 
I felt in it and on account of it all my appetites and 
affections, and in fine I was affected in its parts by pain 
and the titillation of pleasure, and not in the parts of the 
other bodies that were separated from it. But w^hen I 
inquired into the reason why, from this I know not what 
sensation of pain, sadness of mind should follow, and why 
from the sensation of pleasure joy should arise, or why 
this indescribable twitching of the stomach, which I call 
hunger, should put me in mind of taking food, and the 

Existence of Material Things i 3 1 

parchedness of the throat of drink, and so in other cases 
I_ was unable to give any explanation, unless that I was 
so taught_by nature; for there is assuredly no affinity, at 
least none that I am able to comprehend, between this 
irritation of the stomach and the desire of food, any more 
than between the perception of an object that causes pain 
and the consciousness of sadness which sprinc^s from the 
perception. And in_the^ same way it seemed to me that 
all the other judgments I hadToYmed regarding the objects 
of sense, were dictates of nature; because I remarked 
that thoso- judgments were formed in me, before I had 
leisure to weigh and consider the reasons that might 
.constrain me to form them. 

But, afterwards, a wide experience by degrees sapped 
the faith I had reposed in my senses; for I frequently 
observed that towers, which at a distance seemed round, 
appeared square when more closely viewed, and that 
colossal figures, raised on the summits of these towers, 
looked like small statues, when viewed from the bottom 
of them; and, in other instances without number, I also 
discovered error in judgments founded on the external 
senses; and not only in those founded on the external, 
but even in those that rested on the internal senses; for 
is there aught more internal than pain.? and yet I have 
sometimes been informed by parties whose arm or leg 
had been amputated, that they still occasionally seemed 
to feel pain in that part of the body which they had lost, — 
a circumstance that led me to think that I could not be 
quite certain even that any one of my members was 
affected when I felt pain in it. And to thesj grounds of 
doubt I shortly afterwards also added two others of very 
wide generality: the first of them was that I believed 
I never perceived anything when awake which I could not 
occasionally think I also perceived when asleep, and as 
I do not believe that the ideas I seem to perceive in my 
sleep proceed from objects external to me, I did not any 
more observe any ground for believing this of such as I 
seem to perceive when awake; the second was that since 
[ was as yet ignorant of the author of my being, or at 
least supposed myself to be so, I saw nothing to prevent 
my having been so constituted by nature as that I should 



be deceived even in matters that appeared to me to possess 
the greatest truth. And, with respect to the grounds on 
which I had before been persuaded of the existence of 
sensible objects, I had no great difficulty in finding suitable 
answers to them; for as nature seemed to incline me to 
many things from which reason made me averse, I thought 
that I ought not to confide much in its teachings. And 
although the perceptions of the senses were not dependent 
on my will, I did not think that I ought on that ground 
to conclude that they proceeded from things different 
from myself, since perhaps there might be found in me 
, some faculty, though hitherto unknown to me, which 
produced them. 

But now that I begin to know myself better, and to 
discover more clearly the author of my being, I do not, 
indeed, think that I ought rashly to admit all which the 
senses seem to teach, nor, on the other hand, is it my 
conviction that I ought to doubt in general of their 

And, firstly, because I know tha t^alj which I_ clearly 
and distinctly conceive caii be produced by G od exactly as 
T'conceive it. tfjs ^lficie nD£aLJ..a5L^ and i 

distinctly to^bnceive one thing apart from another, in j 
O KfeFt obe certain that the one is different from the other, 
seeing they max-at_least be made to exist separately, ; 
by'tKjDimipotence of God; and it matters not by what 
power this separation is made, in order to be compelled 
to judge them different; and, therefore, merely because I , 
know with certitude that I exist, and because, in the 
meantime, I do not observe that aught necessarily belongs 
to my nature or essence beyond my being a thinking thing, 
"4Sj; rightly conclude that my essence consists only in my 
I being a thinking thing [or a substance whose whole 
l^ssence or nature is merely thinking]. And although I 
may, or rather, as I will shortly say, although I certainly 
do possess a body with which I am very closely conjoined; 
nevertheless, because, on the one hand, I have a clear and 
distinct idea of myself, in as far as I am only a thinking 
and unextended thing, and as, on the other hand, I 
possess a distinct idea of body, in as far as it is only^a* 
extended and unthinking thing , it is certain that I [t hatj 

Existence of Material Things 133 

Js, my mind, by which I am what I am] is entirely anS 
truly distinct from my body, and may exist without it. if 
Moreover, I find in myself diverse faculties of thinking 
that have each their special mode: for example, I find I 
possess the faculties of imagining and perceiving, without 
which I can indeed clearly and distinctly conceive myself 
as entire, but I cannot reciprocally conceive them without 
conceiving myself, that is to say, without an intelligent 
substance in which they reside, for [in the notion we have 
of them, or to use the terms of the schools] in their formal 
concept, they comprise some sort of intellection; whence 
I perceive that they are distinct from myself as modes are 
from things. I remark likewise certain other faculties, as 
the power of changing place, of assuming diverse figures, 
and the like, that cannot be conceived and cannot there- 
fore exist, any more than the preceding, apart from a 
substance in which they inhere. It i2L3££r yLevident. ho w- 
ever ,Jhatthjse faculties, if they really exist, must belong 
to some corporeal or extended substance, since in their 
clear and HisHncf concept there is contained some sort of 

jextension, but no in tellection at alL Farther, I cannot 
doubt but that there is m me a certain passive faculty of 
perception, that is, of receiving and taking knowledge of 
the ideas of sensible things; but this would be useless to 
me, if there did not also exist in me, or in some other thing, 
another active faculty capable of forming and producing 
those ideas. But this active faculty cannot be in me [in 

' as far as I am but a thinking thing], seeing that it does 
not presuppose thought, and also that those ideas are 
frequently produced in my mind without my contributing 
to it in any way, and even frequently contrary to my will. 
This faculty must therefore exist in some substance 
different from me, in which all the objective reality of 
the ideas that are produced by this faculty is contained 
formally or eminently, as I before remarked: and this 
substance is either a body, that is to say, a corporeal 
nature in which is contained formally [and in effect] all 
that is objectively [and by representation] in those ideas; 
or it is God himself, or some other creature, of a rank 
superior to body, in which the same is contained emi- 

I ncntly. But as God is no deceiver, it is manifest that he 



does not of himself and immediately communicate those 
ideas to me, nor even by the intervention of any creature 
in which their objective reality is not formally, but only 
eminently, contained. For as he has given me no faculty 
whereby I can discover this to be the case, but, on the 
contrary, a very strong inclination to believe that those 
ideas arise from corporeal objects, I do not see how he 
could be vindicated from the charge of deceit, if in truth 
they proceeded from any other source, or were produced 
by other causes than corporeal things: and accordingly 
it must be concluded, that^orporeal objects exist. Never- 
theless they are not perhaps exactly such as we perceive by 
the senses, for their comprehension by the senses is, in 
many instances, very obscure and confused; but it is at 
least necessary to admit that all which I clearly and dis- 
tinctly conceive as in them, that is, generally speaking, 
all that is comprehended in the object of speculative 
geometry, really exists external to me. 

But with respect to other things which are either only 
particular, as, for example, that the sun is of such a size 
and figure, etc., or are conceived with less clearness and 
distinctness, as light, sound, pain, and the like, although 
they are highly dubious and uncertain, nevertheless on the 
ground alone that God is no deceiver, and that conse- 
quently he has permitted no falsity in my opinions which 
he has not likewise given me a faculty of correcting, I 
think I may with safety conclude that I possess in myself 
the_ means oJ[^rriying at the truth. And, in the first 
place, it cannoT"Be doubted that in each of the dictates of 
nature there is some truth: for by nature, considered in 
general, I now understand nothing more than God him- 
self, or the order and disposition established by God in 
created things; and by my nature in particular I under- 
stand the assemblage of all that God has given me. 
/ But there is nothing which that nature teaches me more 
(expressly [or more sensibly] than that I have a body 
Vhich is ill affected when I feel pain, and stands in need 
<of food and drink when I experience the sensations of 
hunger and thirst, etc. And therefore I ought not to 
(/^ doubt but that there is some truth in these informations. 
\^ Nature likewise teaches me by these sensations of pain. 

Existence of Material Things 135 

hunger, thirst, etc., that I am not only lodged in my body 
as a pilot in a vessel, but that I am besides so intimately 
conjoined, and as it were intermixed with it, that my 
mind and body compose a ceflaih" unity. For if this were 
not the case, I should not feel pain when my body is hurt, 
seeing I am merely a thinking thing, but should perceive 
the wound by the understanding alone, just as a pilot 
perceives by sight when any part of his vessel is damaged ; 
and when my body has need of food or drink, I should 
have a clear knowledge of this, and not be made aware 
of it by the confused sensations of hunger and thirst: 
for, in truth, all these sensations of hunger, thirst, pain, 
etc., are nothing more than certain confused modes of 
thinking, arising from the union and apparent fusion of 
mind and body. 

Besides this, nature teaches me that my own body is 
surrounded by many other bodies, some of which I have 
to seek after, and others to shun. And indeed, as I per- 
ceive different sorts of colours, sounds, odours, tastes, 
heat, hardness, etc., I safely conclude that there are in 
the bodies from which the diverse perceptions of the 
senses proceed, certain varieties corresponding to them, 
although, perhaps, not in reality like them; and since, 
among these diverse perceptions of the senses, some are 
agreeable, and others disagreeable, there can be no doubt 
that my body, or rather my entire self, in as far as I am 
coniposed of body and mind, may be variously affected, 
Igoth beneficially and hurtfully, by surrounding bodies. 

But there are many other beliefs which, though seem- 
ingly the teaching of nature, are not in reality so, but 
which obtained a place in my mind through a habit of 
judging inconsiderately of things. It may thus easily 
happen that such judgments shall contain error: thus, 
for example, the opinion I have that all space in which 
there is nothing to affect [or make an impression on] my 
senses is void; that in a hot body there is something in 
every respect similar to the idea of heat in my mind ; that 
in a white or green body there is the same whiteness or 
greenness which I perceive ; that in a bitter or sweet body 
there is the same taste, and so in other instances; that 
the stars, towers, and all distant bodies, are of the same 

136 Meditations 

size and figure as they appear to our eyes, etc. But that 
I may avoid everything Hke indistinctness of conception, 
I must accurately define what I properly understand by 
being taught by nature. For nature is here taken in a 
narrower sense than when it signifies the sum of all the 
things which God has giv^n me; seeing that in that 
meaning the notion comprehends much that belongs only 
to the mind [to which I am not here to be understood as 
referring when I use the term nature]; as, for example, 
the notion I have of the truth, that what is done cannot 
be undone, and all the other truths I discern by the 
natural light [without the aid of the body]; and seeing 
that it comprehends likewise much besides that belongs 
only to body, and is not here any more contained under 
the name nature, as the quality of heaviness, and the like, 
of which I do not speak, — the term being reserved exclu- 
sively to designate the things which God has given to me 
as a being composed of mind and body. .But nature,, 
taking the term in the sense explained, teaches me to 
shun what causes in me the sensation of pain, and to 
pursue what affords me the sensation of pleasure, and^ 
other things of this sort; but I do not discover that it 
teaches me, in addition to this, from these diverse per- 
ceptions of the senses, to draw any conclusions respecting 
external objects without a previous [careful and mature] 
consideration of them by the mind: forit iSj^^s^agpears 
to me, the office of the mind alone, and not of the com- 
posite whole of mind and body, to discern the truth in 
those matters. Thus, although the impression a star 
malcerrrrr my eye is not larger than that from the flame 
of a candle, I do not, nevertheless, experience any real or 
positive impulse determining me to believe that the star 
is not greater than the flame; the true account of the 
matter being merely that I have so judged from my youth 
without any rational ground. And, though on approach- 
ing the fire I feel heat, and even pain on approaching it 
too closely, I have, however, from this no ground for 
holding that something resembling, the heat I feel is in 
the fire, any more than that there is something similar 
to the pain; all that I have ground for believing is, that 
there is something in it, whatever it may be, which excites 

Existence of Material Things 1 37 

in me those sensations of heat or pain. So also, although 
there are spaces in which I find nothing to excite and 
affect my senses, I must not therefore conclude that those 
spaces contain in them no body; for I see that in this, as 
in many other similar matters, I have been accustomed 
to pervert the order of nature, because these perceptions 
"of the senses, although given me by nature merely to 
^ signify to my mind what things are beneficial and hurtful 
""to the composite whole of which it is a part, and being 
sufficiently clear and distinct for that purpose, are never- 
theless used by me as infallible rules by which to deter- 
"mine immediately the essence of the bodies that exist out 
of me, of which they can of course afford me only the most 
obscure and confused knowledge. 

But I have already sufficiently considered how it hap- 
pens that, notwithstanding the supreme goodness of God, 
there is falsity in my judgments. A difficulty, however, 
here presents itself, respecting the things which I am 
[ taught by nature must be pursued or avoided, and also 
respecting the internal sensations in which I seem to have 
occasionally detected error [and thus to be directly 
deceived by nature]: thus, for example, I may be so 
deceived by the agreeable taste of some viand with which 
I poison has been mixed, as to be induced to take the poison, 
' In this case, however, nature may be excused, for it simply 
leads me to desire the viand for its agreeable taste, and 
} not the poison, which is unknown to it; and thus we can 
<ihfer nothing from this circumstance beyond that our 
f T/nat^^re is not^mniscicnt : at which there is assuredly no 
'ground for surprise, smce, man being of a fi nite na ture^ his 
knowledg^must-^likewise^e_.o£_ limited But 

we also not unfrequently err in that to which we are 
directly impelled by nature, as is the case with invalids 
who desire drink or food that would be hurtful to them. 
It will here, perhaps, be alleged that the reason why such 
persons are deceived is that their nature is corrupted; 
but this leaves the difficulty untouched, for a sick man is 
not less really the creature of God than a man who is in 
full health; and therefore it is as repugnant to the good- 
ness of God that the nature of the former should be deceit- 
ful as it is for that of the latter to be so. And, as a clock, 



composed of wheels and counter-weights, observes not the 
less accurately all the laws of nature when it is ill made, 
and points out the hours incorrectly, than when it satisfies 
the desire of the maker in every respect; so likewise if the 
body of man be considered as a kind of machine, so made 
up and composed of bones, nerves, muscles, veins, blood, 
and skin, tjiat although th ere werein it no mind, it would >^ 
/ ^till exhibit the same motions~i^ich itatpresent manifests 
I involuntarily, and therefore without the aid of the mind 
\ [and simply by the dispositions of its organs], I easily '^ 
■ discern that it would also be as natural for such a body, 
supposing it dropsical, for example, to experience the 
S parchedness of the throat that is usually accompanied in 
the mind by the sensation of thirst, and to be disposed by 
this parchedness to move its nerves and its other parts in 
the way required for drinking, and thus increase its malady 
and do itself harm, as it is natural for it, when it is not 
indisposed to be stimulated to drink for its good by a> 
similar cause ; and although looking to the use for which 
a clock was destined by its maker, I may say that it is 
deflected from its proper nature when it incorrectly indi- 
cates the hours, and on the same principle, considering 
the machine of the human body as having been fonned by 
God for the sake of the motions which it usually manifests, 
although I may likewise have ground for thinking that it 
does not follow the order of its nature when the throat is 
parched and drink does not tend to its preservation,^^ 
/ nevertheless I yet plainly discern that this latter accepta- 
1 tion of the term nature is very different from the other; 
\. for this is nothing more than a certain denomination, 
/depending entirely on my thought, and hence called 
1 extrinsic, by which I compare a sick man and an imper- 
fectly constructed clock with the idea I have of a man in 
good health and a well-made clock; while by. tliejOLth^ 
acceptation of nature is understood something which is 
\ tni]jjrau]Q3".iDrTKhgv therefore possessed of some 

But certainly, although in respect of a dropsical body, 
it is only by way of exterior denomination that we say its 
nature is corrupted, when, without requiring drink, the 
throat is parched; yet, in respect of the composite whole, 


Existence of Material Things 139 

that is, of the mind in its union with the body, it is not a 
pure denomination, but really an error of nature, for it to 
feel thirst when drink would be hurtful to it: and, accord- 
ingly, it still remains to be considered why it is that the 
goodness of God does not prevent the nature of man thus 
taken from being fallacious. 

To commence this examination accordingly, I here 
remark, in the first place, that there is a vast difference 
between mind^nd body^Jn respect that body, from its 

nature^ is always^Jivisible, and that mind is entirely 

ifidivisible. _Po£^^truth^^ 

is7Wh"enTconsidef myselt m so tar'only as I am a thinking 
thing, I can distinguish in myself no parts, but I very^^. 
clearly discern that I am somewhat absolutely one and 
entire; and although the whole mind seems to be united 
to the whole body, yet, when a foot, an arm, or any other 
part is cut off, I am conscious that nothing has been taken 
from my mind ; nor can the faculties of willing, perceiving,' 
conceiving, etc., properly be called its parts, for it is the 
same mind that is exercised [all entire] in willing, in per- 
ceiving, and in conceiving, etc. But quite the opposite 
holds in corporeal or extended things; for I cannot 
imagine any one of them [how small soever it may be], 
which I cannot easily sunder in thought, and which, 
therefore, I do not know to be divisible. This would be 
sufficient to teach me that the mind or soul of man is 
entirely different from the body, if I had not already been 
apprised of it on other grounds. 

I remark, in the next place, that the mind does not 
immediately receive the impression from all the parts of 
the body, but only from the brain, or perhaps even from 
one small part of it, viz., that in which the common sense 
{sensiis communis) is said to be, which as often as it is 
affected in the same way, gives rise to the same perception 
in the mind, although meanwhile the other parts of the 
body may be diversely disposed, as is proved by innu- 
merable experiments, which it is unnecessary here to 

I remark, besides, that the nature of body is such that 
none of its parts can be moved by another part a little 
removed from the other, which cannot likewise be moved 

140 Meditations 

in the same way by any one of the parts that lie between 
those two, although the most remote part does not act at 
all. As, for example, in the cord a, b, c, d [which is in 
tension], if its last part d be pulled, the first part a will 
not be moved in a different way than it would be were 
one of the intermediate parts b or c to be pulled, and the 
last part d meanwhile to remain fixed. And in the same 
way, when I feel pain in the foot, the science of physics 
teaches me that this sensation is experienced by means of 
the nerves dispersed over the foot, which, extending like 
cords from it to the brain, when they are contracted in the 
foot, contract at the same time the inmost parts of the 
brain in which they have their origin, and excite in these 
parts a certain motion appointed by nature to cause in 
the mind a sensation of pain, as if existing in the foot: but 
as these ner/es must pass through the tibia, the leg, the 
loins, the back, and neck, in order to reach the brain, it 
may happen that although their extremities in the foot 
are not affected, but only certain of their parts that pass 
through the loins or neck, the same movements, neverthe- 
less, are excited in the brain by this motion as would have 
been caused there by a hurt received in the foot, and hence 
the mind will necessarily feel pain in the foot, just as if 
it had been hurt; and the same is true of all the other 
perceptions of our senses. 

I remark^ finally^ that as each of the movements that 
are made in the part of the brain by which the mind is 
immediately..afEected, impresses it with but a single sensa- 
tion, the most likely supposition in the circumstances is, 
that this movement causes the mind to experience, among 
all the sensations which it is capable of impressing upon 
it, that one which is the best fitted, and generally the most 
useful for the preservation of the human body when it is 
in full health. But experience shows us that all the per- 
ceptions which nature has given us are of such a kind 
as I have mentioned; and accordingly, there is nothing 
found in them that does not manifest the power and good- 
ness of God. Thus, for example, when-the nerves of the 
foot are violently or more than usually shaken, the motion 
passing through the medulla of the spine to the innermost 
parts of the brain affords a sign tftjhe mind on which it 

Existence of Material Things 141 

experiences a sensation, viz., of pain, as if it were in the 
foot, by which the mind is admonished and excited to do 
,its utmost to remove the cause of it as dangerous and 
hurtful to the foot. It is true that God could have so 
constituted the nature of man as that the same motion in 
the brain would have informed the mind of something 
altogether different: the motion might, for example, have 
been the occasion on which the mind became conscious 
of itself, in so far as it is in the brain, or in so far as it is in 
some place intermediate between the foot and the brain, 
or, finally, the occasion on which it perceived some other 
object quite different, whatever that might be; but 
nothing of all this would have so well contributed to the 
preservation of the body as that which the mind actually 
feels. In the same way, when we stand in need of drink, 

^ there arises from this want a certain parchedness in the 

f throat that moves its nerves, and by means of them the 
I internal parts of the brain, and this movement affects the 
mind with the sensation of thirst, because there is nothing 
on that occasion which is more useful for us than to be 
made aware that we have need of drink for the preserva- 

i tion of our health; and so in other instances. 

^ Whence it is quite manifest, that notwithstanding the 
sovereign goodness of God, the nature of man, in so far as 
it is composed of mind and body, cannot but be sometimes 
fallacious. For, if there is any cause which excites, not 
in the foot, but in some one of the parts of the nerves that 
stretch from the foot to the brain, or even in the brain 
itself, the same movement that is ordinarily created when 
the foot is ill affected, pain will be felt, as it were, in the 
foot, and the sense will thus be naturally deceived; for 
as the same movement in the brain can but impress the 
mind with the same sensation, and as this sensation is 
much more frequently excited by a cause which hurts the 
foot than by one acting in a different quarter, it is reason- 
able that it should lead the mind to feel pain in the foot 

u rather than in any other part of the body. And if it 
sometimes happens that the parchedness of the throat 

\ does not arise, as is usual, from drink being necessary for 
"the health of the body, but from quite the opposite cause, 
as-'is the ca§e with the dropsical, yet it is much better that 

142 Meditations 

rUghould be deceitful in that instance, than if, on the 
contrary, it were "c'ontTnuaTly TaTTacioiTs "^hen the body 
is well-disposed; and the same holds true in other cases. 
And certainly this consideration is of great service, not 
only in enabling me to recognise the errors to which my 
nature is liable, but likewise in rendering it more easy to 
avoid or correct them: for, knowing that all my senses 
more usually indicate to me what is true than what is 
false, in matters relating to the advantage of the body, 
and being able almost always to make use of more than 
a single sense in examining the same object, and besides 
this, being able to use my memory in connecting present 
with past knowledge, and my understanding which has 
already discovered all the causes of my errors, I ought, no 
longer to fear that falsity may be met with in what is 
daily presented to me by the senses. And I ought to 
reject all the doubts of those bygone days as hyperbolical 
and ridiculous, especially the general uncertainty respect- 
ing sleep, which I could not distinguish from the waking 
state: for I now find a very marked difference between 
the two states, in respect that our memory can never 
connect our dreams with each other and with the course 
of life, in the way it is in the habit of doing with events 
that occur when we are awake. And, in truth, if some 
one, when I am awake, appeared to me all of a sudden 
and as suddenly disappeared, as do the images I see in 
sleep, so that I could not observe either whence he came 
or whither he went, I should not without reason esteem 
it either a spectre or phantom formed in my brain, rather 
than a real man. But when I perceive objects with regard 
to which I can distinctly determine both the place whence 
they come, and that in which they are, and the time at 
which they appear to me, and when, without interruption, 
I can connect the perception I have of them with the 
whole of the other parts of my life, I am perfectly sure 
that what I thus perceive occurs while I am awake and 
not during sleep. And I ought not in the least degree 
to doubt of the truth of those presentations, if, after 
having called together all my senses, my memory, and my 
understanding for the purpose of examining them, no 
deliverance is given by any one of these faculties which 

Existence of Material Things 143 

is repugnant to that of any other: for since God is no 
deceiver, it necessarily follows that I am not herein 
deceived. But because the nec-essities of action fre- 
quently oblige us to come to a determination before we 
have had leisure for so careful an examination, it must 
be confessed that the life of man is frequently obnoxious 
to error with respect to individual objects; and we mustj^ 
in conclusionj.^acknowledg^^ of ouf"na'ture. 







Sir —The version of my Principles which you have been 
at pains to make, is so elegant and finished as to lead me 
to expect that the work will be more generally read in 
French than in Latin, and better understood. The only 
apprehension I entertain is lest the title should deter 
some who have not been brought up to letters, or with 
whom philosophy is in bad repute, because the kind they 
were taught has proved unsatisfactory; and this makes 
me think that it will be useful to add a preface to it for 
the purpose of showing what the matter of the work is, 
what end I had in view in writing it, and what utility may 
be derived from it. But although it might be my part 
to write a preface of this nature, seeing I ought to know 
those particulars better than any other person, I cannot 
nevertheless prevail upon myself to do anything more 
than merely to give a summary of the chief points that 
fall, as I think, to be discussed in it; and I leave it to your 
discretion to present to the public such part of them as 
you shall judge proper. 

I should have desired, in the first place, to explain in 
it what philosophy is, by commencing with the most 
common matters, as, for example, that the word philo- 
sophy signifies the study of wisdom, and that by wisdom 
is to be understood not merely prudence in the manage- 
ment of affairs, but a perfect knowledge of all that man 
can know, as well for the conduct of his life as for the 
'' preservation of his health and the discovery of all the 
arts, and that knowledge to subserve these ends must 
necessarily be deduced from first causes; so that in order 
to study the acquisition of it (which is properly called 


148 The Principles of Philosophy 

philosophising), we must commence with the investiga- 
tion of those first causes which are called Principles. 
Now these principles must possess two conditions : in the 
first place, they must be so clear and evident that the 
human mind, when it attentively considers them, cannot 
doubt of their truth; in the second place, the knowledge 
of other things must be so dependent on them as that 
though the principles themselves may indeed be known 
apart from what depends on them, the latter cannot 
nevertheless be known apart from the former. It will 
accordingly be necessary thereafter to endeavour so to 
deduce from those principles the knowledge of the things 
that depend on them, as that there may be nothing in the 
whole series of deductions which is not perfectly manifest. 
God is in truth the only being who is absolutely wise, that 
is, who possesses a perfect knowledge of all things; but 
we may say that men are more or less wise as their know- 
ledge of the most important truths is greater or less. And 
I am confident that there is nothing, in what I have now 
said, in which all the learned do not concur. 

I should, in the next place, have proposed to consider 
the utility of philosophy, and at the same time have 
shown that, since it embraces all that the human mind 
can know, we ought to believe that it is by it we are 
distinguished from savages and barbarians, and that the 
civilisation and culture of a nation is regulated by the 
degree in which true philosophy flourishes in it, and, 
accordingly, that to contain true philosophers is the 
highest privilege a state can enjoy. Besides this, I should 
have shown that, as regards individuals, it is not only 
useful for each man to have intercourse with those who 
apply themselves to this study, but that it is incomparably 
better he should himself direct his attention to it; just as 
it is doubtless to be preferred that a man should make 
use of his own eyes to direct his steps, and enjoy by 
means of the same the beauties of colour and light, than 
that he should blindly follow the guidance of another;.! 
though the latter course is certainly better than to have 
the eyes closed with no guide except one's self. But to 
live without philosophising is in truth the same as keep- 
ing the eyes closed without attempting to open them ; and 

Preface iaq 

the pleasure of seeing all that sight discloses is not to be 
compared with the satisfaction afforded by the discoveries 
of philosophy. And, finally, this study is more im- 
peratively requisite for the regulation of our manners, 
and for conducting us through life, than is the use of our 
eyes for directing our steps. The brutes, which have 
only their bodies to conserve, are continually occupied in 
seeking sources of nourishment; but men, of whom the 
chief part is the mind, ought to make the search after 
wisdom their principal care, for wisdom is the true 
nourishment of the mind; and I feel assured, moreover, 
that there are very many who would not fail in the 
search, if they would but hope for success in it, and knew 
the degree of their capabilities for it. There is no mind, 
how ignoble soever it be, which remains so firmly bound 
; up in the objects of the senses, as not sometime or other 
j to turn itself away from them in the aspiration after 
' some higher good, although not knowing frequently 
wherein that good consists. The greatest favourites of 
! fortune — those w^ho have health, honours, and riches in 
abundance — are not more exempt from aspirations of 
this nature than others; nay, I am persuaded that these 
I are the persons who sigh the most deeply after another 
good greater and more perfect still than any they already 
possess. But the supreme good, considered by natural 
reason without the light of faith, is nothing more than 
the knowledge of truth through its first causes, in other 
words, the wisdom of which philosophy is the study. 
And, as all these particulars are indisputably true, all 
that is required to gain assent to their truth is that they 
be well stated. 

But as one is restrained from assenting to these 
doctrines by experience, which shows that they who make 
pretensions to philosophy are often less wise and reason- 
able than others who never appHed themselves to the study, 
I should have here shortly explained wherein consists all 
[ the science we now possess, and what are the degrees of 
wisdom at which we have arrived. The first degree 
contains only notions so clear of themselves that they can 
be acquired without meditation; the second compre- 
hends all that the experience of the senses dictates; the 

150 The Principles of Philosophy 

third, that which the conversation of other men teaches 
us; to which may be added as the fourth, the reading, not 
of all books, but especially of such as have been written 
by persons capable of conveying proper instruction, for 
it is a species of conversation we hold with their authors. 
And it seems to me that all the wisdom we in ordinary 
possess is acquired only in these four ways; for I do not 
class divine revelation among them, because it does not 
conduct us by degrees, but elevates us at once to an 
infallible faith. 

There have been, indeed, in all ages great minds who 
endeavoured to find a fifth road to wisdom, incom- 
parably more sure and elevated than the other four. 
The path they essayed was the search of first causes and 
true principles, from which might be deduced the reasons 
of all that can be known by man; and it is to them the 
appellation of philosophers has been more especially 
accorded. I am not aware that there is any one of them 
up to the present who has succeeded in this enterprise. 
The first and chief whose writings we possess, are Plato 
and Aristotle, between whom there was no difference, 
except that the former, following in the footsteps of his 
master, Socrates, ingenuously confessed that he had never 
yet been able to find anything certain, and that he was 
contented to write what seemed to him probable, 
imagining, for this end, certain principles by which he 
endeavoured to account for the other things. Aristotle, 
on the other hand, characterised by less candour, although 
for twenty years the disciple of Plato, and with no prin- 
ciples beyond those of his master, completely reversed 
his mode of putting them, and proposed as true and 
certain what it is probable he himself never esteemed as 
such. But these two men had acquired much judgment 
and wisdom by the four preceding means, qualities which 
raised their authority very high, so much so that those 
who succeeded them were willing rather to acquiesce in 
their opinions, than to seek better for themselves. The 
chief question among their disciples, however, was as to 
whether we ought to doubt of all things or hold some as 
certain, — a dispute which led them on both sides into 
extravagant errors; for a part of those who were for 

Preface i r i 

doubt, extended it even to the actions of life, to the 
neglect of the most ordinary rules required for its conduct; 
those, on the other hand, who maintained the doctrine of 
certainty, supposing that it must depend upon the senses, 
trusted entirely to them. To such an extent was this 
carried by Epicurus, that it is said he ventured to affirm, 
contrary to all the reasonings of the astronomers, that 
the sun is no larger than it appears. 

It is a fault we may remark in most disputes, that, as 
truth is the niean between the two opinions that are 
upheld, each disputant departs from it in proportion to 
the degree in which he possesses the spirit of contradiction. 
But the error of those who leant too much to the side of 
doubt, was not followed for any length of time, and that 
of the opposite party has been to some extent corrected 
by the doctrine that the senses are deceitful in many 
instances. Nevertheless, I do not know that this error 
was wholly removed by showing that certitude is not in 
the senses, but in the understanding alone when it has 
clear perceptions; and that while we only possess the 
knowledge which is acquired in the first four grades of 
wisdom, we ought not to doubt of the things that appear 
to be true in what regards the conduct of life, nor esteem 
them as so certain that we cannot change our opinions 
regarding them, even though constrained by the evidence 
of reason. 

From ignorance of this truth, or, if there was any one 
to whom it was known, from neglect of it, the majority 
of those who in these later ages aspired to be philosophers, 
blindly followed Aristotle, so that they frequently cor- 
rupted the sense of his writings, and attributed to him 
various opinions which he would not recognise as his own 
were he now to return to the world; and those who did 
not follow him, among whom are to be found many of the 
greatest minds, did yet not escape being imbued with his 
opinions in their youth, as these form the staple of instruc- 
tion in the schools; and thus their minds were so pre- 
occupied that they could not rise to the knowledge of true 
principles. And though I hold all the philosophers in 
esteem, and am unwilling to incur odium by my censure, 
I can adduce a proof of my assertion, which I do not think 

152 The Principles of Philosophy 

any of them will gainsay, which is, that they all laid down 
as a principle what they did not perfectly know. For 
example, I know none of them who did not suppose that 
there was gravity in terrestrial bodies; but although 
experience shows us very clearly that bodies we call heavy 
descend towards the centre of the earth, we do not, there- 
fore, know the nature of gravity, that is, the cause or 
principle in virtue of which bodies descend, and we must 
derive our knowledge of it from some other source. The 
same may be said of a vacuum and atoms, of heat and 
cold, of dryness and humidity, and of salt, sulphur, and 
mercury, and the other things of this sort which some 
have adopted as their principles. But no conclusion 
deduced from a principle which is not clear can be evident, 
even although the deduction be formally valid; and 
hence it follows that no reasonings based on such prin- 
ciples could lead them to the certain knowledge of any 
one thing, nor consequently advance them one step in 
the search after wisdom. And if they did discover any 
truth, this was due to one or other of the four means above 
mentioned. Notwithstanding this, I am in no degree 
desirous to lessen the honour which each of them can 
justly claim; I am only constrained to say, for the con- 
solation of those who have not given their attention to 
study, that just as in travelling, when we turn our back 
upon the place to which we were going, we recede the 
farther from it in proportion as we proceed in the new 
direction for a greater length of time and with greater 
speed, so that, though we may be afterwards brought 
back to the right way, we cannot nevertheless arrive at the 
destined place as soon as if we had not moved backwards 
at all; so in philosophy, when we make use of false prin- 
ciples, we depart the farther from the knowledge of truth 
and wisdom exactly in proportion to the care with which 
we cultivate them, and apply ourselves to the deduction 
of diverse consequences from them, thinking that we are 
philosophising well, while we are only departing the 
farther from the truth; from which it must be inferred 
that they who have learned the least of all that has been 
hitherto distinguished by the name of philosophy are the 
most fitted for the apprehension of truth. 

Preface i r ^ 

After making those matters clear, I should, in the next 
place, have desired to set forth the grounds for holding 
that the true principles by which we may reach that 
highest degree of wisdom wherein consists the sovereign 
good of human life, are those I have proposed in this 
work; and two considerations alone are sufficient to 
establish this— the first of which is, that these principles 
are very clear, and the second, that we can deduce all 
other truths from them; for it is only these two con- 
ditions that are required in true principles. But I easily 
prove that they are very clear; firstly, by a reference to 
the manner in which I found them, namely, by rejecting 
all propositions that were in the least doubtful, for it is 
certain that such as could not be rejected by this test 
when they were attentively considered, are the most 
evident and clear which the human mind can know. Thus 
by considering that he who strives to doubt of all is unable 
nevertheless to doubt that he is while he doubts, and that 
what reasons thus, in not being able to doubt of itself 
and doubting nevertheless of everything else, is not that 
which we call our body, but what we name our mind or 
thought, I have taken the existence of this thought for 
the first principle, from which I very clearly deduced the 
following truths, namely, that there is a God who is the 
author of all that is in the world, and who, being the 
source of all truth, cannot have created our understanding 
of such a nature as to be deceived in the judgments it 
forms of the things of which it possesses a very clear and 
distinct perception. Those are all the principles of which 
I avail myself touching immaterial or metaphysical 
objects, from which I most clearly deduce these other 
principles of physical or corporeal things, namely, that 
there are bodies extended in length, breadth, and depth, 
which are of diverse figures and are moved in a variety 
of ways. Such are in sum the principles from which I 
deduce all other truths. The second circumstance that 
proves the clearness of these principles is, that they have 
been known in all ages, and even received as true and 
indubitable by all men, with the exception only of the 
existence of God, which has been doubted by some, 
because they attributed too much to the perceptions 


154 The Principles ot Philosophy 

of the senses^ and God can neither be seen nor 

But, though all the truths which I class among my 
principles were known at all times, and by all men, never- 
theless, there has been no one up to the present, who, so 
far as I know, has adopted them as principles of philo- 
sophy: in other words, as such that we can deduce from 
them the knowledge of whatever else is in the world. It 
accordingly now remains for me to prove that they are 
such ; and it appears to me that I cannot better establish 
this than by the test of experience: in other words, by 
inviting readers to peruse the following work. For, 
though I have not treated in it of all matters — that being 
impossible — I think I have so explained all of which I had 
occasion to treat, that they who read it attentively will 
have ground for the persuasion that it is unnecessary to 
seek for any other principles than those I have given, in 
order to arrive at the most exalted knowledge of which 
the mind of man is capable ; especially if, after the perusal 
of my writings, they take the trouble to consider how 
many diverse questions are therein discussed and ex- 
plained, and, referring to the writings of others, they see 
how little probability there is in the reasons that are 
adduced in explanation of the same questions by prin- 
ciples different from mine. And that they may the more 
easily undertake this, I might have said that those imbued 
with my doctrines have much less difficulty in compre- 
hending the writings of others, and estimating their true 
value, than those who have not been so imbued ; and this 
is precisely the opposite of what I before said of such as 
commenced with the ancient philosophy, namely, that 
the more they have studied it the less fit are they for 
rightly apprehending the truth. 

I should also have added a word of advice regarding the 
manner of reading this work, which is, that I should wish 
the reader at first to go over the whole of it, as he would 
a romance, without greatly straining his attention, or 
tarrying at the difficulties he may perhaps meet with in 
it, with the view simply of knowing in general the matters 
of which I treat ; and that afterwards, if they seem to him 
to merit a more careful examination, and he feel a desire 

Preface irr 

to know their causes, he may read it a second time, in 
order to observe the connection of my reasonings; but 
that he must not then give it up in despair, ahhough he 
may not everywhere sufficiently discover the connection 
of the proof, or understand all the reasonings— it being 
only necessary to mark with a pen the places where the 
difficulties occur, and continue to read without inter- 
ruption to the end; then, if he does not grudge to take up 
the book a third time, I am confident he will find in a 
fresh perusal the solution of most of the difficulties he 
will have marked before; and that, if any still remain, 
their solution will in the end be found in another 

I have observed, on examining the natural constitutions 
of different minds, that there are hardly any so dull or 
slow of understanding as to be incapable of apprehending 
good opinions, or even of acquiring all the highest sciences, 
if they be but conducted along the right road. And this 
can also be proved by reason; for, as the principles are 
clear, and as nothing ought to be deduced from them, 
unless most manifest inferences, no one is so devoid of 
intelligence as to be unable to comprehend the conclusions 
that flow from them. But, besides the entanglement of 
prejudices, from which no one is entirely exempt, although 
it is they who have been the most ardent students of the 
false sciences that receive the greatest detriment from 
them, it happens very generally that people of ordinary 
capacity neglect to study from a conviction that they 
want ability, and that others, who are more ardent, press 
on too rapidly: whence it comes to pass that they fre- 
quently admit principles far from evident, and draw 
doubtful inferences from them. For this reason, I should 
wish to assure those who are too distrustful of their own 
ability that there is nothing in my writings which they 
may not entirely understand, if they only take the trouble 
to examine them; and I should wish, at the same time, to 
warn those of an opposite tendency that even the most 
superior minds will have need of much time and attention 
to remark all I designed to embrace therein. 

After this, that I might lead men to understand the real 
design I had in publishing them, I should have wished 

156 The Principles ot Philosophy 

here to explain the order which it seems to me one ought 
to follow with the view of instructing himself. In the 
first place, a man who has merely the vulgar and imperfect 
knowledge which can be acquired by the four means above 
explained, ought, before all else, to endeavour to form for 
himself a code of morals sufficient to regulate the actions 
of his life, as well for the reason that this does not admit 
of delay as because it ought to be our first care to live 
well. In the next place, he ought to study logic, not that 
of the schools, for it is only, properly speaking, a dialectic 
which teaches the mode of expounding to others what we 
already know, or even of speaking much, without judg- 
ment, of what we do not know, by which means it corrupts 
rather than increases good sense — but the logic which 
teaches the right conduct of the reason with the view of 
discovering the truths of which we are ignorant; and, 
because it greatly depends on usage, it is desirable he 
should exercise himself for a length of time in practising 
its rules on easy and simple questions, as those of the 
mathematics. Then, when he has acquired some skill in 
discovering the truth in these questions, he should com- 
mence to apply himself in earnest to true philosophy, of 
which the first part is metaphysics, containing the prin- 
ciples of knowledge, among which is the explication of the 
principal attributes of God, of the immateriality of the 
soul, and of all the clear and simple notions that are in us; 
the second is physics, in which, after finding the true 
principles of material things, we examine, in general, how 
the whole universe has been framed; in the next place, 
we consider, in particular, the nature of the earth, and of 
all the bodies that are most generally found upon it, as air, 
water, fire, the loadstone and other minerals. In the next 
place, it is necessary also to examine singly the nature of 
plants, of animals, and above all of man, in order that we 
may thereafter be able to discover the other sciences that 
are useful to us. Thus, all philosophy is like a tree, of 
which metaphysics is the root, physics the trunk, and all 
the other sciences the branches that grow out of this 
trunk, which are reduced to three principal, namely, 
medicine, mechanics, and ethics. By the science of morals 
I understand the highest and most perfect which, pre- 

Preface 1^7 

supposing an entire knowledge of the other sciences, is 
the last degree of wisdom. 

But as it is not from the roots or the trunks of trees that 
we gather the fruit, but only from the extremities of 
their branches, so the principal utility of philosophy 
depends on the separate uses of its parts, which we can 
only learn last of all. But, though I am ignorant of 
almost all these, the zeal I have always felt in endeavour- 
ing to be of service to the public was the reason why I 
published, some ten or twelve years ago, certain essays on 
the doctrines I thought I had acquired. The first part of 
these essays was a '' Discourse on the Method of rightly 
conducting the Reason, and seeking Truth in the Sciences," 
in which I gave a summary of the principal rules of logic, 
and also of an imperfect ethic, which a person may follow 
provisionally so long as he does not know any better. 
The other parts were three treatises : the first of Dioptrics, 
the second of Meteors, and the third of Geometry. In the 
Dioptrics, I designed to show that we might proceed far 
enough in philosophy as to arrive, by its means, at the 
knowledge of the arts that are useful to life, because the 
invention of the telescope, of which I there gave an ex- 
planation, is one of the most difficult that has ever been 
made. In the treatise of Meteors, I desired to exhibit the 
difference that subsists between the philosophy I cultivate 
and that taught in the schools, in which the same matters 
are usually discussed. In fine, in the Geometry, I pro- 
fessed to demonstrate that I had discovered many things 
that were before unknown, and thus afford ground for 
believing that we may still discover many others, with the 
view of thus stimulating all to the investigation of truth. 
Since that period, anticipating the difficulty which many 
would experience in apprehending the foundations of the 
metaphysics, I endeavoured to explain the chief points 
of them in a book of Meditations, which is not in itself 
large, but the size of which has been increased, and the 
matter greatly illustrated, by the objections which several 
very learned persons sent to me on occasion of it, and by 
the replies which I made to them. At length, after it 
appeared to me that those preceding treatises had suffi- 
ciently prepared the minds of my readers for the Principles 

158 The Principles of Philosophy 

of Philosophy , I also published it; and I have divided this 
work into four parts, the first of which contains the prin- 
ciples of human knowledge, and which may be called the 
First Philosophy, or Metaphysics. That this part, accord- 
ingly, may be properly understood, it will be necessary 
to read beforehand the book of Meditations I wrote on the 
same subject. The other three parts contain all that is 
most general in physics, namely, the explication of the 
first laws or principles of nature, and the way in which the 
heavens, the fixed stars, the planets, comets, and generally 
the whole universe, were composed; in the next place, 
the explication, in particular, of the nature of this earth, 
the air, water, fire, the magnet, which are the bodies we 
most commonly find everywhere around it, and of all the 
qualities we observe in these bodies, as light, heat, gravity, 
and the like. In this way, it seems to me, I have com- 
menced the orderly explanation of the whole of philo- 
sophy, without omitting any of the matters that ought to 
precede the last which I discussed. 

But to bring this undertaking to its conclusion, I ought 
hereafter to explain, in the same manner, the nature of the 
other more particular bodies that are on the earth, namely, 
minerals, plants, animals, and especially man; finally, 
to treat thereafter with accuracy of medicine, ethics, and 
mechanics. I should require to do this in order to give to 
the world a complete body of philosophy; and I do not 
yet feel myself so old, — I do not so much distrust my 
strength, nor do I find myself so far removed from the 
knowledge of what remains, as that I should not dare to 
undertake to complete this design, provided I were in a 
position to make all the experiments which I should 
require for the basis and verification of my reasonings. 
But seeing that would demand a great expenditure, to 
which the resources of a private individual like myself 
would not be adequate, unless aided by the public, and 
as I have no ground to expect this aid, I believe that I 
ought for the future to content myself with studying for 
my own instruction, and posterity will excuse me if I fail 
hereafter to labour for them. 

Meanwhile, that it may be seen wherein I think I have 
already promoted the general good, I will here mention the 

Preface i^^ 

fruits that may be gathered from my principles. The 
first is the satisfaction which the mind will experience on 
finding in the work many truths before unknown; for 
although frequently truth does not so greatly affect our 
imagination as falsity and fiction, because it seems less 
wonderful and is more simple, yet the gratification it 
affords is always more durable and solid. The second 
fruit is, that in studying these principles we will become 
accustomed by degrees to judge better of all the things 
we come in contact with, and thus be made wiser, in which 
respect the effect will be quite the opposite of the common 
philosophy, for we may easily remark in those we call 
pedants that it renders them less capable of rightly 
exercising their reason than they would have been if they 
had never known it. The third is, that the truths which 
they contain, being highly clear and certain, will take away 
all ground of dispute, and thus dispose men's minds to 
gentleness and concord ; whereas the contrary is the effect 
of the controversies of the schools, which, as they insen- 
sibly render those who are exercised in them more 
wrangling and opinionative, are perhaps the prime cause 
of the heresies and dissensions that now harass the world. 
The last and chief fruit of these principles is that one will 
be able, by cultivating them, to discover many truths I 
myself have not unfolded, and thus passing by degrees 
from one to another, to acquire in course of time a perfect 
knowledge of the whole of philosophy, and to rise to the 
highest degree of wisdom. For just as all the arts, though 
in their beginnings they are rude and imperfect, are yet 
gradually perfected by practice from their containing at 
first something true, and whose effect experience evinces; 
so in philosophy, when we have true principles, we cannot 
fail by following them to meet sometimes with other truths ; 
and we could not better prove the falsity of those of 
Aristotle, than by saying that men made no progress in 
knowledge by their means during the many ages they 
prosecuted them. 

I well know that there are some men so precipitate and 
accustomed to use so little circumspection in what they 
do, that, even with the most solid foundations, they could 
not rear a firm superstructure; and as it is usually those 

i6o The Principles of Philosophy 

who are the readiest to make books, they would in a short 
time mar all that I have done, and introduce uncertainty 
and doubt into my manner of philosophising, from which 
I have carefully endeavoured to banish them, if people 
were to receive their writings as mine, or as representing 
my opinions. I had, not long ago, some experience of 
this in one of those who were believed desirous of following 
me the most closely,^ and one too of whom I had some- 
where said that I had such confidence in his genius as to 
believe that he adhered to no opinions which I should not 
be ready to avow as mine; for he last year published a 
book entitled Fundatnenta Physicce, in which, although 
he seems to have written nothing on the subject of physics 
and medicine which he did not take from my writings, as 
well from those I have published as from another still 
imperfect on the nature of animals, which fell into his 
hands; nevertheless, because he has copied them badly, 
and changed the order, and denied certain metaphysical 
truths upon which all physics ought to be based, I am 
obliged wholly to disavow his work, and here to request 
readers not to attribute to me any opinion unless they 
find it expressly stated in my own writings, and to receive 
no opinion as true, whether in my writings or elsewhere, 
unless they see that it is very clearly deduced from true 

I well know, likewise, that many ages may elapse ere 
all the truths deducible from these principles are evolved 
out of them, as well because the greater number of such 
as remain to be discovered depend on certain particular 
experiments that never occur by chance, but which require 
to be investigated with care and expense by men of the 
highest intelligence, as because it will hardly happen that 
the same persons who have the sagacity to make a right 
use of them, will possess also the means of making them, 
and also because the majority of the best minds have 
formed so low an estimate of philosophy in general, from 
the imperfections they have remarked in the kind in vogue 
up to the present time, that they cannot apply themselves 
to the search after truth. 

* Regius; see La Vie de M. Descartes, reduite en abrege ( Bailie t). 
Liv. vii., chap. vii. — Tr, 

Preface 1 6 1 

*• But, in conclusion, if the difference discernible between 
the principles in question and those of every other system, 
and the great array of truths deducible from them, lead 
them to discern the importance of continuing the search 
after these truths, and to observe the degree of wisdom, the 
perfection and felicity of Hfe, to which they are fitted to 
conduct us, I venture to believe that there will not be 
found one who is not ready to labour hard in so profitable 
a study, or at least to favour and aid with all his might 
those who shall devote themselves to it with success. 

The height of my wishes is, that posterity may some- 
time behold the happy issue of it, etc. 






Madam, — The greatest advantage I have derived from the 
writings which I have already pubHshed, has arisen from 
my having, through means of them, become known to 
your highness, and thus been privileged to hold occa- 
sional converse with one in whom so many rare and 
estimable qualities are united, as to lead me to believe 
I should do service to the public by proposing them as an 
example to posterity. It would ill become me to flatter, 
or to give expression to anything of which I had no certain 
knowledge, especially in the first pages of a work in which 
I aim at laying down the principles of truth. And the 
generous modesty that is conspicuous in all your actions, 
assures me that the frank and simple judgment of a man 
who only writes what he believes will be more agreeable 
to you than the ornate laudations of those who have 
studied the art of compliment. For this reason, I will 
give insertion to nothing in this letter for which I have 
not the certainty both of experience and reason; and 
in the exordium, as in the rest of the work, I will write 
only as becomes a philosopher. There is a vast difference 
between real and apparent virtues; and there is also 
a great discrepancy between those real virtues that 
proceed from an accurate knowledge of the truth, and such 
as are accompanied with ignorance or error. The virtues 
I call apparent are only, properly speaking, vices, which, 
as they are less frequent than the vices that are opposed 
to them, and are farther removed from them than the 
intermediate virtues, are usually held in higher esteem 
than those virtues. Thus, because those who fear dangers 
too much are more numerous than they who fear them' 
too little, temerity is frequently opposed to the vice of 
timidity, and taken for a virtue, and is commonly more 
highly esteemed than true fortitude. Thus, also, the 


Dedication 169 

prodigal are in ordinary more praised than the Hberal; 
and none more easily acquire a great reputation for piety 
than the superstitious and hypocritical. With regard to 
true virtues, these do not all proceed from true knowledge, 
for there are some that likewise spring from defect or 
error: thus, simplicity is frequently the source of good- 
ness, fear of devotion, and despair of courage. The 
virtues that are thus accompanied with some imperfec- 
tions differ from each other, and have received diverse 
appellations. But those pure and perfect virtues that 
arise from the knowledge of good alone, are all of the 
same nature, and may be comprised under the single 
term wisdom. For, whoever owns the firm and constant 
resolution of always using his reason as well as lies in his 
power, and in all his actions of doing what he judges to be 
best, is truly wise, as far as his nature permits; and by 
this alone he is just, courageous, temperate, and possesses 
I all the other virtues, but so well balanced as that none 
i of them appears more prominent than another: and for 
this reason, although they are much more perfect than 
the virtues that blaze forth through the mixture of some 
defect, yet, because the crowd thus observes them less, 
they are not usually extolled so highly. Besides, of the 
two things that are requisite for the wisdom thus de- 
scribed, namely, the perception of the understanding and 
the disposition of the will, it is only that which lies in the 
will which all men can possess equally, inasmuch as the 
understanding of some is inferior to that of others. But 
although those who have only an inferior understanding 
may be as perfectly wise as their nature permits, and 
may render themselves highly acceptable to God by their 
virtue, provided they preserve always a firm and constant 
resolution to do all that they shall judge to be right, and 
to omit nothing that may lead them to the knowledge 
of the duties of which they are ignorant; nevertheless, 
those who preserve a constant resolution of performing 
the right, and are especially careful in instructing them- 
' selves, and who possess also a highly perspicacious 
intellect, arrive doubtless at a higher degree of wisdom 
!: than others; and I see that these three particulars are 
■ found in great perfection in your highness. For, in the 

164 The Principles of Philosophy 

first place, your desire of self-instruction is manifest, 
from the circumstance that neither the amusements of 
the court, nor the accustomed mode of educating ladies, 
which ordinarily condemns them to ignorance, have been 
sufficient to prevent you from studying with much care 
all that is best in the arts and sciences; and the incom- 
parable perspicacity of your intellect is evinced by this, 
that you penetrated the secrets of the sciences and 
acquired an accurate knowledge of them in a very short 
period. But of the vigour of your intellect I have a still 
stronger proof, and one peculiar to myself, in that I have 
never yet met any one who understood so generally and 
so well as yourself all that is contained in my writings. 
For there are several, even among men of the highest 
intellect and learning, who find them very obscure. And 
I remark, in almost all those who are versant in meta- 
physics, that they are wholly disinclined from geometry; 
and, on the other hand, that the cultivators of geometry 
have no ability for the investigations of the first philo- 
sophy : insomuch that I can say with truth I know but one 
mind, and that is your own, to which both studies are alike 
congenial, and which I therefore, with propriety, desig- 
nate incomparable. But what most of all enhances my 
admiration is, that so accurate and varied an acquaintance 
with the whole circle of the sciences is not found in some 
aged doctor who has employed many years in contem- 
plation, but in a princess still young, and whose counte- 
nance and years would more fitly represent one of the 
graces than a muse or the sage Minerva. In conclusion, 
I not only remark in your highness all that is requisite 
on the part of the mind to perfect and sublime wisdom, 
but also all that can be required on the part of the will 
or the manners, in which benignity and gentleness are so 
conjoined with majesty that, though fortune has attacked 
you with continued injustice, it has failed either to irritate 
or crush you. And this constrains me to such veneration 
that I not only think this work due to you, since it treats j 
of philosophy which is the study of wisdom, but likewise 
feel not more zeal for my reputation as a philosopher than 
pleasure in subscribing myself, — Of your most serene 
highness, the most devoted servant, Descartes. 





I. That in order to seek truth, it is necessary once in the 
[course of our Hfe to doubt, as far as possible, of all things. 
As we were at one time children, and as we formed 
various judgments regarding the objects presented to our 
senses, when as yet we had not the entire use of our reason, 
numerous prejudices stand in the way of our arriving 
at the knowledge of truth; and of these it seems im- 
possible for us to rid ourselves, unless we undertake, once 
in our lifetime, to doubt of all those things in which we 
may discover even the smallest suspicion of uncertainty. 

II. That we ought also to consider as false all that is 

Moreover, it will be useful likewise to esteem as false 
the things of which we shall be able to doubt, that we 
may with greater clearness discover what possesses most 
certainty and is the easiest to know. 

III. That we ought not meanwhile to make use of doubt 
in the conduct of life. 

In the meantime, it is to be observed that we are to avail 
ourselves of this general doubt only while engaged in the 
contemplation of truth. For, as far as concerns the con- 
duct of life, we are very frequently obliged to follow 
opinions merely probable, or even sometimes, though of 
two courses of action we may not perceive more proba- 
bility in the one than in the other, to choose one or other, 
seeing the opportunity of acting would not unfrequently 
pass away before we could free ourselves from our doubts. 

IV. Why we may doubt of sensible things. 


1 66 The Principles of Philosophy 

Accordingly, since we now only design to apply our- 
selves to the investigation of truth, we will doubt, first, 
whether of all the things that have ever fallen under our 
senses, or which we have ever imagined, any one really 
exists ; in the first place, because we know by experience 
that the senses sometimes err, and it would be imprudent 
to trust too much to what has even once deceived us; 
secondly, because in dreams we perpetually seem to 
perceive or imagine innumerable objects which have no 
existence. And to one who has thus resolved upon a 
general doubt, there appear no marks by which he can 
with certainty distinguish sleep from the waking state. 

V. Why we may also doubt of mathematical demon- 

We will also doubt of the other things we have before 
held as most certain, even of the demonstrations of mathe- 
matics, and of their principles which we have hitherto 
deemed self-evident; in the first place, because we have 
sometimes seen men fall into error in such matters, and 
admit as absolutely certain and self-evident what to us 
appeared false, but chiefly because we have learnt that 
God who created us is all-powerful; for we do not yet 
know whether perhaps it was his will to create us so that 
we are always deceived, even in the things we think we 
know best: since this does not appear more impossible 
than our being occasionally deceived, which, however, as 
observation teaches us, is the case. And if we suppose 
that an all-powerful God is not the author of our being, 
and that we exist of ourselves or by some other means, 
still, the less powerful we suppose our author to be, the 
greater reason will we have for believing that we are not 
so perfect as that we may not be continually deceived. 

VI. That we possess a free-will, by which we can with- 
hold our assent from what is doubtful, and thus avoid 

But meanwhile, whoever in the end may be the author 
of our being, and however powerful and deceitful he may 
be, we are nevertheless conscious of a freedom, by which 
we can refrain from admitting to a place in our belief 
aught that is not manifestly certain and undoubted, and 
thus guard against ever being deceived. 

Human Knowledge 167 

VII. That we cannot doubt of our existence while we 
doubt, and that this is the first knowledge we acquire 
when we philosophise in order. 

While we thus reject all of which we can entertain the 
smallest doubt, and even imagine that it is false, we easily 
indeed suppose that there is neither God, nor sky, nor 
bodies, and that we ourselves even have neither hands 
nor feet, nor, finally, a body; but we cannot in the same 
way suppose that we are not while we doubt of the truth 
of these things; for there is a repugnance in conceiving 
that what thinks does not exist at the very time when 
it thinks. Accordingly, the knowledge, / think, therefore 
I am, is the first and most certain that occurs to one who 
philosophises orderly. 

VIII. That we hence discover the distinction between 
the mind and the body, or between a thinking and cor- 
poreal thing. 

And this is the best mode of discovering the nature of 
the mind, and its distinctness from the body: for examin- 
ing what we are, while supposing, as we now do, that 
there is nothing really existing apart from our thought, 
we clearly perceive that neither extension, nor figure, nor ^ 
local motion,^ nor anything similar that can be attributed 
to body, pertains to our nature, and nothing save thought 
alone; and, consequently, that the notion we have of 
our mind precedes that of any corporeal thing, and is 
more certain, seeing we still doubt whether there is any 
body in existence, while we already perceive that we think. 

IX. What thought (cogttatto) is. 

By the word thought, I understand all that which so 
takes place in us that we of ourselves are immediately 
conscious of it; and, accordingly, not only to understand 
{intelligere, entendre), to will {velle), to imagine (tmaginari), 
but even to perceive (sentire, sentir), are here the same as 
to think {cogitare, penser). For if I say, I see, or, I walk, 
therefore I am; and if I understand by vision or walking 
the act of my eyes or of my limbs, which is the work of 
the body, the conclusion is not absolutely certain, because, 
as is often the case in dreams, I may think that I see or 

1 Instead of " local motion," the French has " existence in any 

1 68 The Principles of Philosophy 

walk, although I do not open my eyes or move from my 
place, and even, perhaps, although I have no body: but, 
if I mean the sensation itself, or consciousness of seeing or 
walking, the knowledge is manifestly certain, because 
it is then referred to the mind, which alone perceives or 
is conscious that it sees or walks.^ i^.^ 

X. That the notions which are simplest and self- 
evident, are obscured by logical definitions; and that 
such are not to be reckoned among the cognitions acquired 
by study [but as born with us]. 

I do not here explain several other terms which I have 
used, or design to use in the sequel, because their meaning 
seems to me sufficiently self-evident. And I frequently 
remarked that philosophers erred in attempting to explain, 
by logical definitions, such truths as are most simple and 
self-evident; for they thus only rendered them more 
obscure. And when I said that the proposition, I think, 
therefore I am, is of all others the first and most certain 
which occurs to one philosophising orderly, I did not 
therefore deny that it was necessary to know what thought, 
existence, and certitude are, and the truth that, in order 
to think it is necessary to be, and the like; but, because 
these are the most simple notions, and such as of them- 
selves afford the knowledge of nothing existing, I did not 
judge it proper there to enumerate them. 

XL How we can know our mind more clearly than our 

But now that it may be discerned how the knowledge 
we have of the mind not only precedes, and has greater 
certainty, but is even clearer, than that we have of the 
body, it must be remarked, as a matter that is highly 
manifest by the natural light, that to nothing no affections 
or qualities belong; and, accordingly, that where we 
observe certain affections, there a thing or substance to 
which these pertain, is necessarily found. The same light 
also shows us that we know a thing or substance more 
clearly in proportion as we discover in it a greater number 
of qualities. Now, it is manifest that we remark a greater 
number of qualities in our mind than in any other thing; 

^ In the French, *' which alone has the power of perceiving, or of 
being conscious in any other way whatever.*' 

Human Knowledge 169 

for there is no occasion on which we know anything 
whatever when we are not at the same time led with much 
greater certainty to the knowledge of our own mind. 
For example, if I judge that there is an earth because I 
touch or see it, on the same ground, and with still greater 
reason, I must be persuaded that my mind exists; for it 
may be, perhaps, that I think I touch the earth while 
there is none in existence; but it is not possible that I 
should so judge, and my mind which thus judges not 
exist; and the same holds good of whatever object is 
presented to our mind. 

XII. How it happens that every one does not come 
equally to know this. 

Those who have not philosophised in order have had 
other opinions on this subject, because they never dis- 
tinguished with sufficient care the mind from the body. 
For, although they had no difficulty in believing that they 
themselves existed, and that they had a higher assurance 
of this than of any other thing, nevertheless, as they did 
not observe that by themselves, they ought here to under- 
stand their minds alone [when the question related to 
metaphysical certainty] ; and since, on the contrary, they 
rather meant their bodies which they saw with their 
eyes, touched with their hands, and to which they erro- 
neously attributed the faculty of perception, they were 
prevented from distinctly apprehending the nature of the 

XIII. In what sense the knowledge of other things 
depends upon the knowledge of God. 

But when the mind, which thus knows itself but is still 
in doubt as to all other things, looks around on all sides, 
with a view to the farther extension of its knowledge, it 
first of all discovers within itself the ideas of many things; 
and while it simply contemplates them, and neither 
affirms nor denies that there is anything beyond itself 
corresponding to them, it is in no danger of erring. The 
mind also discovers certain common notions out of which 
it frames various demonstrations that carry conviction 
to such a degree as to render doubt of their truth im- 
possible, so long as we give attention to them. For 
example, the mind has within itself ideas of numbers and 

170 The Principles of Philosophy 

figures, and it has likewise among its common notions 
the principle that if equals be added to equals the wholes 
will be equal, and the like ; from which it is easy to demon- 
strate that the three angles of a triangle are equal to 
two right angles, etc. Now, so long as we attend to the 
premises from which this conclusion and others similar 
to it were deduced, we feel assured of their truth; but, 
as the mind cannot always think of these with attention, 
when it has the remembrance of a conclusion without 
recollecting the order of its deduction, and is uncertain 
whether the author of its being has created it of a nature 
that is liable to be deceived, even in what appears most 
evident, it perceives that there is just ground to distrust 
the truth of such conclusions, and that it cannot possess 
any certain knowledge until it has discovered its author. 

XIV. That we may validly infer the existence of God 
from necessary existence being comprised in the concept 
we have of him. 

When the mind afterwards reviews the different ideas 
that are in it, it discovers what is by far the chief among 
them — that of a Being omniscient, all-powerful, and 
absolutely perfect; and it observes that in this idea there 
is contained not only possible and contingent existence, 
as in the ideas of all other things which it clearly perceives, 
but existence absolutely necessary and eternal. And 
just as because, for example, the equality of its three 
angles to two right angles is necessarily comprised in the 
idea of a triangle, the mind is firmly persuaded that the 
three angles of a triangle are equal to two right angles; 
so, from its perceiving necessary and eternal existence 
to be comprised in the idea which it has of an all-perfect 
Being, it ought manifestly to conclude that this all-perfect 
Being exists. 

XV. That necessary existence is not in the same way 
comprised in the notions which we have of other things, 
but merely contingent existence. 

The mind will be still more certain of the truth of this 
conclusion, if it consider that it has no idea of any other 
thing in which it can discover that necessary existence 
is contained; for, from this circumstance alone, it will 
discern that the idea of an all-perfect Being has not been 

Human Knowledge 171 

framed by itself, and that it does not represent a chimera, 
but a true and immutable nature, which must exist since 
it can only be conceived as necessarily existing. 

XVI. That prejudices hinder many from clearly know- 
ing the necessity of the existence of God. 

Our mind would have no difficulty in assenting to this 
truth, if it were, first of all, wholly free from prejudices; 
but as we have been accustomed to distinguish, in all 
other things, essence from existence, and to imagine at 
will many ideas of things which neither are nor have been, 
it easily happens, when we do not steadily fix our thoughts 
on the contemplation of the all-perfect Being, that a 
doubt arises as to whether the idea we have of him is 
not one of those which we frame at pleasure, or at least 
of that class to whose essence existence does not pertain. 

XVII. That the greater objective (representative) per- 
fection there is in our idea of a thing, the greater also 
must be the perfection of its cause. 

When we further reflect on the various ideas that are 
in us, it is easy to perceive that there is not much dif- 
ference among them, when we consider them simply as 
certain modes of thinking, but that they are widely 
different, considered in reference to the objects they 
represent; and that their causes must be so much the 
more perfect according to the degree of objective perfec- 
tion contained in them.^ For there is no difference 
between this and the case of a person who has the idea 
of a machine, in the construction of which great skill is 
displayed, in which circumstances we have a right to 
inquire how he came by this idea, whether, for example, 
he somewhere saw such a machine constructed by another, 
or whether he was so accurately taught the mechanical 
sciences, or is endowed with such force of genius, that he 
was able of himself to invent it, without having elsewhere 
seen anything like it; for all the ingenuity which is con- 
tained in the idea objectively only, or as it were in a 
picture, must exist at least in its first and chief cause, 
whatever that may be, not only objectively or repre- 
sentatively, but in truth formally or eminently. 

^ *' as what they represent of their object has more perfection." — 

172 The Principles of Philosophy 

XVIII. That the existence of God may be again 
inferred from the above. 

Thus, because we discover in our minds the idea of God, 
or of an all-perfect Being, we have a right to inquire into 
the source whence we derive it; and we will discover that 
the perfections it represents are so immense as to render 
it quite certain that we could only derive it from an all- 
perfect Being; that is, from a God really existing. For 
it is not only manifest by the natural light that nothing 
cannot be the cause of anything whatever, and that the 
more perfect cannot arise from the less perfect, so as to 
be thereby produced as by its efficient and total cause, 
but also that it is impossible we can have the idea or 
representation of anything whatever, unless there be 
somewhere, either in us or out of us, an original which 
comprises, in reality, all the perfections that are thus 
represented to us; but, as we do not in any way find in 
ourselves those absolute perfections of which we have the 
idea, we must conclude that they exist in some nature 
different from ours, that is, in God, or at least that they 
were once in him; and it most manifestly follows [from 
their infinity] that they are still there. 

XIX. That, although we may not comprehend the 
nature of God, there is yet nothing which we know so 
clearly as his perfections. 

This will appear sufficiently certain and manifest to 
those who have been accustomed to contemplate the idea 
of God, and to turn their thoughts to his infinite perfec- 
tions; for, although we may not comprehend them, 
because it is of the nature of the infinite not to be com- 
prehended by what is finite, we nevertheless conceive 
them more clearly and distinctly than material objects, 
for this reason, that, being simple, and unobscured by 
limits,^ they occupy our mind more fully. 

XX. That we are not the cause of ourselves, but that 
this is God, and consequently that there is a God. 

* After limits^ " what of them we do conceive is much less con- 
fused. There is, besides, no speculation more calculated to aid 
in perfecting our understanding, and which is more important 
than this, inasmuch as the consideration of an object that has no 
limits to its perfections, fills us with satisfaction and assurance.** — 

Human Knowledge 173 

But, because every one has not observed this, and 
because, when we have an idea of any machine in which 
great skill is displayed, we usually know with sufficient 
accuracy the manner in which we obtained it, and as we 
cannot even recollect when the idea we have of a God 
was communicated to us by him, seeing it was always in 
our minds, it is still necessary that we should continue 
our review, and make inquiry after our author, possessing, 
as we do, the idea of the infinite perfections of a God: 
for it is in the highest degree evident by the natural light, 
that that which knows something more perfect than 
itself, is not the source of its own being, since it would 
thus have given to itself all the perfections which it knows; 
and that, consequently, it could draw its origin from no 
other being than from him who possesses in himself all 
those perfections, that is, from God. 

XXI. That the duration alone of our life is sufficient 
to demonstrate the existence of God. 

The truth of this demonstration will clearly appear, 
provided we consider the nature of time, or the duration 
of things ; for this is of such a kind that its parts are not 
mutually dependent, and never co-existent; and, accord- 
ingly, from the fact that we now are, it does not neces- 
sarily follow that we shall be a moment afterwards, unless 
some cause, viz., that which first produced us, shall, as it 
were, continually reproduce us, that is, conserv^e us. For 
we easily understand that there is no power in us by 
which we can conserve ourselves, and that the being who 
has so much power as to conserve us out of himself, must 
also by so much the greater reason conserve himself, or 
rather stand in need of being conserved by no one what- 
ever, and, in fine, be God. 

XXII. That in knowing the existence of God, in the 
manner here explained, we likewise know all his attributes, 
as far as they can be known by the natural light alone. 

There is the great advantage in proving the existence of 
God in this way, viz., by his idea, that we at the same time 
know what he is, as far as the weakness of our nature 
allows; for, reflecting on the idea we have of him which 
is bom with us, we perceive that he is eternal, omniscient, 
omnipotent, the source of all goodness and truth, creator 

174 The Principles of Philosophy 

of all things^ and that,? in fine^ he has in himself all that in 
which we can clearly discover any infinite perfection or 
good that is not limited by any imperfection. 

XXIII. That God is not corporeal, and does not 
perceive by means of senses as we do, or will the evil 
of sin. 

For there are indeed many things in the world that are 
to a certain extent imperfect or limited, though possess- 
ing also some perfection; and it is accordingly impossible 
that any such can be in God. Thus, looking to corporeal 
nature,^ since divisibility is included in local extension, 
and this indicates imperfection, it is certain that God is 
not body. And although in men it is to some degree a 
perfection to be capable of perceiving by means of the 
senses, nevertheless since in every sense there is passivity^ 
which indicates dependency, we must conclude that God 
is in no manner possessed of senses, and that he only 
understands and wills, not, however, like us, by acts 
in any way distinct, but always by an act that is one, 
identical, and the simplest possible, understands, wills, 
and operates all, that is, all things that in reality exist; 
for he does not will the evil of sin, seeing this is but the 
negation of being. 

XXIV. That in passing from the knowledge of God to 
the knowledge of the creatures, it is necessary to remember 
that our understanding is finite, and the power of God 

But as we know that God alone is the true cause of all 
that is or can be, we will doubtless follpw the best way of 
philosophising, if, from the knowledge we have of God 
himself, we pass to the explication of the things which he 
has created, and essay to deduce it from the notions that 
are naturally in our minds, for we will thus obtain the most 
perfect science, that is, the knowledge of effects through 
their causes. But that we may be able to make this 
attempt with sufficient security from error, we must use 
the precaution to bear in mind as much as possible that 

^ In the French, ** since extension constitutes the nature of 

* In the French, " because our perceptions arise from impressions 
made upon us from another source," i.e., than ourselves. 

Human Knowledge 17 r 

God, who is the author of things, is infinite, while we are 
wholly finite. 

XXV. That we must believe all that God has revealed 
although it may surpass the reach of our faculties. ' 

Thus, if perhaps God reveal to us or others, matters 
concerning himself which surpass the natural powers of 
our mind, such as the mysteries of the incarnation and of 
the trinity, we will not refuse to believe them, although we 
may not clearly understand them; nor will we be in any 
way surprised to find in the immensity of his nature, or 
even in what he has created, many things that exceed our 

XXVI. That it is not needful to enter into disputes ^ 
regarding the infinite, but merely to hold all that in which 
we can find no limits as indefinite, such as the extension 
of the world, the divisibihty of the parts of matter, the 
number of the stars, etc. 

We will thus never embarrass ourselves by disputes 
about the infinite, seeing it would be absurd for us who 
are finite to undertake to determine anything regarding 
it, and thus as it were to limit it by endeavouring to 
comprehend it. We will accordingly give ourselves no 
concern to reply to those who demand whether the half 
of an infinite line is also infinite, and whether an infinite 
number is even or odd, and the like, because it is only 
such as imagine their minds to be infinite who seem bound 
to entertain questions of this sort. And, for our part, 
looking to all those things in which in certain senses we 
discover no limits, we will not, therefore, affirm that they 
are infinite, but will regard them simply as indefinite. 
Thus, because we cannot imagine extension so great that 
we cannot still conceive greater, we will say that the 
magnitude of possible things is indefinite, and because a 
body cannot be divided into parts so small that each of 
these may not be conceived as again divided into others 
still smaller, let us regard quantity as divisible into parts 
whose number is indefinite; and as we cannot imagine so 
many stars that it would seem impossible for God to 
create more, let us suppose that their number is indefinite, 
and so in other instances. 

^ *• to essay to comprehend the infinite.*' — French, 

176 The Principles of Philosophy 

XXVII. What difference there is between the indefinite 
and the infinite. 

And we will call those things indefinite rather than 
infinite, with the view of reserving to God alone the 
appellation of infinite; in the first place, because not 
only do we discover in him alone no limits on any side, 
but also because we positively conceive that he admits of 
none; and in the second place, because we do not in the 
same way positively conceive that other things are in 
every part unlimited, but merely negatively admit that 
their limits, if they have any, cannot be discovered by us. 

XXVIII. That we must examine, not the final, but the 
efficient, causes of created things. 

Likewise, finally, we will not seek reasons of natural 
things from the end which God or nature proposed to 
himself in their creation {i.e., final causes),^ for we ought 
not to presume so far as to think that we are sharers in 
the counsels of Deity, but, considering him as the efficient 
cause of all things, let us endeavour to discover by the 
natural light ^ which he has planted in us, applied to those 
of his attributes of which he has been willing we should 
have some knowledge, what must be concluded regarding 
those effects we perceive by our senses ; bearing in mind, 
however, what has been already said, that we must only 
confide in this natural light so long as nothing contrary 
to its dictates is revealed by God himself.^ 

XXIX. That God is not the cause of our errors. 

The first attribute of God which here falls to be con- 
sidered, is that he is absolutely veracious and the source 
of all light, so that it is plainly repugnant for him to 
deceive us, or to be properly and positively the cause of 
the errors to which we are consciously subject; for 
although the address to deceive seems to be some mark of 
subtlety of mind among men, yet without doubt the will 
to deceive only proceeds from malice or from fear and 
weakness, and consequently cannot be attributed to God. 

^ " We will not stop to consider the ends which God proposed 
to himself in the creation of the world, and we will entirely reject 
from our philosophy the search of final causes." — French, 

* ** Faculty of reasoning." — French, 

• The last clause, beginning ** bearing in mind," is omitted in 
the French. 

Human Knowledge 177 

XXX. That consequently all which we clearly perceive 
is true, and that we are thus delivered from the doubts 
above proposed. 

Whence it follows, that the light of nature, or faculty of 
knowledge given us by God, can never compass any object 
which is not true, in as far as it attains to a knowledge 
of it, that is, in as far as the object is clearly and distinctly 
apprehended. For God would have merited the appella- 
tion of a deceiver if he had given us this faculty perverted, 
and such as might lead us to take falsity for truth [when 
we used it aright]. Thus the highest doubt is removed, 
which arose from our ignorance on the point as to whether 
perhaps our nature was such that we might be deceived 
even in those things that appear to us the most evident. 
The same principle ought also to be of avail against all 
the other grounds of doubting that have been already 
enumerated. For mathematical truths ought now to be 
above suspicion, since these are of the clearest. And if 
we perceive anything by our senses, whether while awake 
or asleep, we will easily discover the truth, provided we 
separate what there is of clear and distinct in the know- 
ledge from what is obscure and confused. There is no 
need that I should here say more on this subject, since 
it has already received ample treatment in the metaphysi- 
cal Meditations; and what follows will serve to explain 
it still more accurately. 

XXXI. That our errors are, in respect of God, merely 
negations, but, in respect of ourselves, privations. 

But as it happens that we frequently fall into error, 
although God is no deceiver, if we desire to inquire into 
the origin and cause of our errors, with a view to guard 
against them, it is necessary to observe that they depend 
less on our understanding than on our will, and that they 
have no need of the actual concourse of God, in order to 
their production; so that, when considered in reference to 
God, they are merely negations, but in reference to our- 
selves, privations. 

XXXII. That there are only two modes of thinking in 
us, viz., the perception of the understanding and the 
action of the will. 

For all the modes of thinking of which we are conscious 


178 The Principles of Philosophy 

may be referred to two general classes, the one of which 
is the perception or operation of the understanding, and 
the other the volition or operation of the will. Thus, to 
perceive by the senses (senttre), to imagine, and to con- 
ceive things purely intelligible,® are only different modes 
of perceiving (percipiendt); but to desire, to be averse 
from, to afhrm, to deny, to doubt, are different modes of 

XXXIII. That we never err unless when we judge of 
something which we do not sufficiently apprehend. 

When we apprehend anything we are in no danger of 
error, if we refrain from judging of it in any way; and 
even when we have formed a judgment regarding it, we 
would never fall into error, provided we gave our assent 
only to what we clearly and distinctly perceived; but 
the reason why we are usually deceived, is that we judge 
without possessing an exact knowledge of that of which 
we judge. 

XXXIV. That the will as well as the understanding is 
required for judging. 

I admit that the understanding is necessary for judging, 
there being no room to suppose that we can judge of that 
which wc in no way apprehend; but the will also is 
required in order to our assenting to what we have in any 
degree perceived. It is not necessary, however, at least 
to form any judgment whatever, that we have an entire 
and perfect apprehension of a thing; for we may assent 
to many things of which we have only a very obscure and 
confused knowledge. 

XXXV. That the will is of greater extension than the 
understanding, and is thus the source of our errors. 

Further, the perception of the intellect extends only to 
the few things that are presented to it, and is always very 
limited: the will, on the other hand, may, in a certain 
sense, be said to be infinite, because we observe nothing 
that can be the object of the will of any other, even of 
the unlimited will of God, to which ours cannot also 
extend, so that we easily carry it beyond the objects we 
clearly perceive ; and when we do this, it is not wonderful 
that we happen to be deceived. 

XXXVI. That our errors cannot be imputed to God. 

Human Knowledge 170 

But although God has not given us an omniscient 
understanding, he is not on this account to be considered 
in any wise the author of our errors, for it is of the nature 
of created intellect to be finite, and of finite intellect not 
to embrace all things. 

XXXVII. That the chief perfection of man is his being 
able to act freely or by will, and that it is this which 
renders him worthy of praise or blame. 

That the will should be the more extensive is in 
harmony with its nature; and it is a high perfection in 
man to be able to act by means of it, that is, freely; and 
thus in a peculiar way to be the master of his own actions, 
and merit praise or blame. For self-acting machines are 
not commended because they perform with exactness 
all the movements for which they were adapted, seeing 
their motions are carried on necessarily; but the maker 
of them is praised on account of the exactness with 
which they were framed, because he did not act of neces- 
sity, but freely; and, on the same principle, we must 
attribute to ourselves something more on this account, 
that when we embrace truth, we do so not of necessity, 
but freely. 

XXXVIII. That error is a defect in our mode of acting, 
not in our nature; and that the faults of their subjects 
may be frequently attributed to other masters, but never 
to God. 

It is true, that as often as we err, there is some defect 
in our mode of action or in the use of our liberty, but not 
in our nature, because this is always the same, whether 
our judgments be true or false. And although God could 
have given to us such perspicacity of intellect that we 
should never have erred, we have, notwithstanding, no 
right to demand this of him; for, although with us he 
who was able to prevent evil and did not is held guilty of 
it, God is not in the same way to be reckoned responsible 
for our errors because he had the power to prevent them, 
inasmuch as the dominion which some men possess oyer 
others has been instituted for the purpose of enabling 
them to hinder those under them from doing evil, whereas 
the dominion which God exercises over the universe is 
perfectly absolute and free. For this reason we ought to 

i8o The Principles of Philosophy 

thank him for the goods he has given us, and not complain 
that he has not blessed us with all which we know it was 
in his power to impart. 

XXXIX. That the liberty of our will is self-evident. 

Finally, it is so manifest that we possess a free will, 
capable of giving or withholding its assent, that this truth 
must be reckoned among the first and most common 
notions which are born with us. This, indeed, has already 
very clearly appeared, for when essaying to doubt of all 
things we went so far as to suppose even that he who 
created us employed his limitless power in deceiving us 
in every way, we were conscious nevertheless of being 
free to abstain from believing what was not in every 
respect certain and undoubted. But that of which we 
are unable to doubt at such a time is as self-evident and 
clear as anything we can ever know. 

XL. That it is likewise certain that God has fore- 
ordained all things. 

But because what we have already discovered of God, 
gives us the assurance that his power is so immense that 
we would sin in thinking ourselves capable of ever doing 
anything which he had not ordained beforehand, we 
should soon be embarrassed in great difficulties if we 
undertook to harmonise the pre-ordination of God with the 
freedom of our will, and endeavoured to comprehend both 
truths at once. 

XLI. How the freedom of our will may be reconciled 
with the Divine pre-ordination. 

But, in place of this, we will be free from these embar- 
rassments if we recollect that our mind is limited, while 
the power of God, by which he not only knew from all 
eternity what is or can be, but also willed and pre-ordained 
it, is infinite. It thus happens that we possess sufficient 
intelligence to know clearly and distinctly that this power 
is in God, but not enough to comprehend how he leaves 
the free actions of men indeterminate; and, on the other 
hand, we have such consciousness of the liberty and 
indifference which exists in ourselves, that there is 
nothing we more clearly or perfectly comprehend [so 
that the omnipotence of God ought not to keep us from 
believing it]. For it would be absurd to doubt of that of 

Human Knowledge i8i 

which we are fully conscious, and which we experience as 
existing m ourselves, because we do not comprehend 
another matter which, from its very nature, we know to 
be incomprehensible. 

XLII. How, although we never will to err, it is never- 
theless by our will that we do err. 

But new since we know that all our errors depend upon 
our will, and as no one wishes to deceive himself, it may 
seem wonderful that there is any error in our judgments 
at all. It is necessary to remark, however, that there is 
a great difference between willing to be deceived, and 
willing to yield assent to opinions in which it happens 
that error is found. For though there is no one who 
expressly wishes to fall into error, we will yet hardly find 
any one who is not ready to assent to things in which, 
unknown to himself, error lurks; and it even frequently 
happens that it is the desire itself of following after truth 
that leads those not fully aware of the order in which it 

I ought to be sought for, to pass judgment on matters of 

i which they have no adequate knowledge, and thus to fall 

I nto error. 

\ XLIII. That we shall never err if we give our assent 
only to what we clearly and distinctly perceive. 

But it is certain we will never admit falsity for truth, 
so long as we judge only of that which we clearly and 
distinctly perceive; because, as God is no deceiver, the 
faculty of knowledge which he has given us cannot be 
fallacious, nor, for the same reason, the faculty of will, 
when we do not extend it beyond the objects we clearly 
know. And even although this truth could not be estab- 
lished by reasoning, the minds of all have been so im- 
pressed by nature as spontaneously to assent to whatever 
is clearly perceived, and to experience an impossibility to 
doubt of its truth. 

XLIV. That we uniformly judge improperly when we 
assent to what we do not clearly perceive, although our 
judgment may chance to be true; and that it is frequently 
our memory which deceives us by leading us to believe 
that certain things were formerly sufficiently understood 
by us. 

It is likewise certain that, when we approve of any 


1 82 The Principles of Philosophy 

reason which we do not apprehend, we are either deceived, 
or, if we stumble on the truth, it is only by chance, and 
thus we can never possess the assurance that we are not 
in error. I confess it seldom happens that we judge of a 
thing when we have observed we do not apprehend it, 
because it is a dictate of the natural light never to judge 
of what we do not know. But we most frequently err in 
this, that we presume upon a past knowledge of much to 
which we give our assent, as to something treasured up 
in the memory, and perfectly known to us; whereas, in 
truth, we have no such knowledge. 

XLV. What constitutes clear and distinct perception. 

There are indeed a great many persons who, through 
their whole lifetime, never perceive anything in a way 
necessary for judging of it properly; for the knowledge 
upon which we can establish a certain and indubitable 
judgment must be not only clear, but also distinct. I call 
that clear which is present and manifest to the mind giving 
attention to it, just as we are said clearly to see objects 
when, being present to the eye looking on, they stimulate 
it with sufficient force, and it is disposed to regard them; 
but the distinct is that which is so precise and different 
from all other objects as to comprehend in itself only what 
is clear.^ 

XLVI. It is shown, from the example of pain, that a 
perception may be clear without being distinct, but that 
it cannot be distinct unless it is clear. 

For example, when any one feels intense pain, the 
knowledge which he has of this pain is very clear, but it 
is not always distinct; for men usually confound it with 
the obscure judgment they form regarding its nature, and 
think that there is in the suffering part something similar 
to the sensation of pain of which they are alone conscious. 
And thus perception may be clear without being distinct, 
but it can never be distinct without likewise being clear. 

XLVII. That, to correct the prejudices of our early 
years, we must consider what is clear in each of our 
simple 2 notions. 

* " what appears manifestly to him who considers it as he ought.** 
— French. 

» •• first.'*— Ff^nc;i. 

Human Knowledge 18-2 

And, indeed, in our early years, the mind was so im- 
mersed in the body, that, although it perceived many 
thmgs with sufficient clearness, it yet knew nothing dis- 
tinctly; and since even at that time we exercised our 
judgment in many matters, numerous prejudices were 
thus contracted, which, by the majority, are never after- 
wards laid aside. But that we may now be in a position 
to get rid of these, I will here briefly enumerate all the 
simple notions of which our thoughts are composed, and 
distinguish in each what is clear from what is obscure, 
or fitted to lead into error. 

XL VIII. That all the objects of our knowledge are to 
be regarded either (i) as things or the affections of things: 
or (2) as eternal truths; with the enumeration of things. 

Whatever objects fall under our knowledge we con- 
sider either as things or the affections of things,^ or as 
eternal truths possessing no existence beyond our thought. 
Of the first class the most general are substance, duration, 
order, number, and perhaps also some others, which 
notions apply to all the kinds of things. I do not, how- 
ever, recognise more than two highest kinds {summa 
genera) of things; the first of intellectual things, or such 
as have the power of thinking, including mind or thinking 
substance and its properties; the second, of material 
things, embracing extended substance, or body and its 
properties. Perception, volition, and all modes as well 
of knowing as of willing, are related to thinking substance; 
on the other hand, to extended substance we refer magni- 
tude, or extension in length, breadth, and depth, figure, 
motion, situation, divisibility of parts themselves, and 
the like. There are, however, besides these, certain 
things of which we have an internal experience that ought 
not to be referred either to the mind of itself, or to the 
body alone, but to the close and intimate union between 
them, as will hereafter be shown in its place. Of this 
class are the appetites of hunger and thirst, etc., and also 
the emotions or passions of the mind which are not exclu- 
sively mental affections, as the emotions of anger, joy, 

1 Things and the affections of things are (in the French) equiva- 
lent to " what has some {i.e, a real) existence," as opposed to the 
class of " eternal truths," which have merely an ideal existence. 

184 The Principles of Philosophy- 
sadness, love, etc.; and, finally, all the sensations, as of 
pain, titillation, light and colours, sounds, smells, tastes, 
heat, hardness, and the other tactile qualities. 

XLIX. That the eternal truths cannot be thus enumer- 
ated, but that this is not necessary. 

What I have already enumerated we are to regard as 
things, or the qualities or modes of things. We now come 
to speak of eternal truths. When we apprehend that it is 
impossible a thing can arise from nothing, this proposition, 
ex nihilo nihil fit, is not considered as somewhat existing, 
or as the mode of a thing, but as an eternal truth having 
its seat in our mind, and is called a common notion or 
axiom. Of this class are the following: — It is impossible 
the same thing can at once be and not be; what is done 
cannot be undone; he who thinks must exist while he 
thinks; and innumerable others, the whole of which it is 
indeed difficult to enumerate, but this is not necessary, 
since, if blinded by no prejudices, we cannot fail to know 
them when the occasion of thinking them occurs. 

L. That these truths are clearly perceived, but not 
equally by all men, on account of prejudices. 

And, indeed, with regard to these common notions, it is 
not to be doubted that they can be clearly and distinctly 
known, for otherwise they would not merit this appella- 
tion: as, in truth, some of them are not, with respect to all 
men, equally deserving of the name, because they are not 
equally admitted by all: not, however, from this reason, 
as I think, that the faculty of knowledge of one man 
extends farther than that of another, but rather because 
these common notions are opposed to the prejudices 
of some, who, on this account, are not able readily to 
embrace them, even although others, who are free from 
those prejudices, apprehend them with the greatest 

LI. What substance is, and that the term is not appli- 
cable to God and the creatures in the same sense. 

But with regard to what wc consider as things or the 
modes of things, it is worth while to examine each of them 
by itself. By substance we can conceive nothing else 
than a thing which exists in such a way as to stand in 
need of nothing beyond itself in order to its existence. 

Human Knowledge 185 

And, in truth, there can be conceived but one substance 
which is absolutely independent, and that is God. We 
perceive that all other things can exist only by help of the 
concourse of God. And, accordingly, the term substance 
does not apply to God and the creatures univocally, to 
adopt a term familiar in the schools; that is, no significa- 
tion of this word can be distinctly understood which is 
common to God and them. 

LII. That the term is applicable univocally to the mind 
and the body, and how substance itself is known. 

Created substances, however, whether corporeal or 
thinking, may be conceived under this common concept; 
for these are things which, in order to their existence, 
stand in need of nothing but the concourse of God. But 
yet substance cannot be first discovered merely from its 
being a thing which exists independently, for existence by 
itself is not observed by us. We easily, however, dis- 
cover substance itself from any attribute of it, by this 
common notion, that of nothing there are no attributes, 
properties, or qualities: for, from perceiving that some 
attribute is present, we infer that some existing thing or 
substance to which it may be attributed is also of necessity 

|. LIII. That of every substance there is one principal 
attribute, as thinking of the mind, extension of the 

But, although any attribute is sufficient to lead us to 
the knowledge of substance, there is, however, one prin- 
cipal property of ever)-' substance, which constitutes its 
nature or essence, and upon which all the others depend. 
Thus, extension in length, breadth, and depth, constitutes 
the nature of corporeal substance; and thought the nature 
of thinking substance. For every other thing that can 
be attributed to body, presupposes extension, and is only 
some mode of an extended thing; as all the properties 
we discover in the mind are only diverse modes of thinking. 
Thus, for example, we cannot conceive figure unless in 
something extended, nor motion unless in extended space, 
nor imagination, sensation, or will, unless in a thinking 
thing. But, on the other hand, we can conceive extension 
without figure or motion, and thought without imagination 

1 86 The Principles of Philosophy 

or sensation, and so of the others; as is clear to any one 
who attends to these matters. 

LIV. How we may have clear and distinct notions of 
the substance which thinks, of that which is corporeal, 
and of God. 

And thus we may easily have two clear and distinct 
notions or ideas, the one of created substance, which 
thinks, the other of corporeal substance, provided we 
carefully distinguish all the attributes of thought from 
those of extension. We may also have a clear and dis- 
tinct idea of an uncreated and independent thinking 
substance, that is, of God, provided we do not suppose 
that this idea adequately represents to us all that is in 
God, and do not mix up with it anything fictitious, but 
attend simply to the characters that are comprised in the 
notion we have of him, and which we clearly know to 
belong to the nature of an absolutely perfect Being. For 
no one can deny that there is in us such an idea of God, 
without groundlessly supposing that there is no know- 
ledge of God at all in the human mind. 

LV. How duration, order, and number may be also 
distinctly conceived. 

We will also have most distinct conceptions of duration, 
order, and number, if, in place of mixing up with our 
notions of them that which properly belongs to the con- 
cept of substance, we merely think that the duration of 
a thing is a mode under which we conceive this thing, in 
so far as it continues to exist; and, in like manner, that 
order and number are not in reality different from things 
disposed in order and numbered, but only modes under 
which we diversely consider these things. 

LVI. What are modes, qualities, attributes. 

And, indeed, we here understand by modes the same 
with what we elsewhere designate attributes or qualities. 
But when we consider substance as affected or varied by 
them, we use the term modes; when from this variation 
it may be denominated of such a kind, we adopt the term 
qualities [to designate the different modes which cause it 
to be so named]; and, finally, when we simply regard 
these modes as in the substance, we call them attributes. 
Accordingly, since God must be conceived as superior to 

Human Knowledge 187 

change, it is not proper to say that there are modes or 
quahties in him, but simply attributes; and even in 
created things that which is found in them always in the 
same mode, as existence and duration in the thing which 
exists and endures, ought to be called attribute, and not 
mode or quality. 

LVII. That some attributes exist in the things to which 
they are attributed, and others only in our thought; and 
what duration and time are. 

Of these attributes or modes there are some which exist 
in the things themselves, and others that have only an 
existence in our thought; thus, for example, time, which 
we distinguish from duration taken in its generality, and 
call the measure of motion, is only a certain mode under 
which we think duration itself, for we do not indeed con- 
ceive the duration of things that are moved to be different 
from the duration of things that are not moved: as is 
evident from this, that if two bodies are in motion for 
an hour, the one moving quickly and the other slowly, 
we do not reckon more time in the one than in the other, 
although there may be much more motion in the one of the 
bodies than in the other. But that we may comprehend 
the duration of all things under a common measure, we 
compare their duration with that of the greatest and most 
regular motions that give rise to years and days, and 
which we call time; hence what is so designated is nothing 
superadded to duration, taken in its generality, but a 
mode of thinking. 

LVIII. That number and all universals are only modes 
of thought. 

In the same way number, when it is not considered as 
in created things, but merely in the abstract or in general, 
is only a mode of thinking; and the same is true of all 
those general ideas we call universals. 

LIX. How universals are formed; and what are the 
five common, viz., genus, species, difference, property, and 

Universals arise merely from our making use of one and 
the same idea in thinking of all individual objects between 
which there subsists a certain likeness; and when we 
comprehend all the objects represented by this idea under 

1 88 The Principles of Philosophy 

one name, this term likewise becomes universal. For 
example, when we see two stones, and do not regard their 
nature farther than to remark that there are two of them,: 
we form the idea of a certain number, which we call the 
binary; and when we afterwards see two birds or two 
trees, and merely take notice of them so far as to observe 
that there are two of them, we again take up the same idea 
as before, which is, accordingly, universal; and we like- 
wise give to this number the same universal appellation of 
binary. In the same way, when we consider a figure of 
three sides, we form a certain idea, which we call the idea 
of a triangle, and we afterwards make use of it as the 
universal to represent to our mind all other figures of three 
sides. But when we remark more particularly that of 
figures of three sides, some have a right angle and others 
not, we form the universal idea of a right-angled triangle, 
which being related to the preceding as more general, may 
be called species; and the right angle the universal dif- 
ference by which right-angled triangles are distinguished 
from all others; and farther, because the square of the 
side which sustains the right angle is equal to the squares 
of the other two sides, and because this property belongs 
only to this species of triangles, we may call it the universal 
property of the species. Finally, if we suppose that of 
these triangles some are moved and others not, this 
will be their universal accident; and, accordingly, we 
commonly reckon five universals, viz., genus, species, 
difference, property, accident. 

LX. Of distinctions; and first of the real. 

But number in things themselves arises from the dis-. 
tinction there is between them: and distinction is three- 
fold, viz., real, modal, and of reason. The real properly 
subsists between two or more substances; and it is suffi- 
cient to assure us that two substances are really mutually 
distinct, if only we are able clearly and distinctly to 
conceive the one of them without the other. For the 
knowledge we have of God renders it certain that he can 
effect all that of which we have a distinct idea: wherefore, 
since we have now, for example, the idea of an extended 
and corporeal substance, though we as yet do not know 
with certainty whether any such thing is really existent^ 

Human Knowledge 189 

nevertheless, merely because we have the idea of it, we 
may be assured that such may exist; and, if it really 
exists, that every part which we can determine by thought 
must be really distinct from the other parts of the same 
substance. In the same way, since every one is conscious 
that he thinks, and that he in thought can exclude from 
himself every other substance, whether thinking or 
extended, it is certain that each of us thus considered is 
really distinct from every other thinking and corporeal 
substance. And although we suppose that God united 
a body to a soul so closely that it was impossible to form 
a more intimate union, and thus made a composite whole, 
the two substances would remain really distinct, notwith- 
standing this union; for with whatever tie God connected 
them, he was not able to rid himself of the power he 
possessed of separating them, or of conserving the one 
apart from the other, and the things which God can 
separate or conserve separately are really distinct. 

LXI. Of the modal distinction. 

There are two kinds of modal distinctions, viz., that 
between the mode properly so called and the substance 
of which it is a mode, and that between two modes of the 
same substance. Of the former we have an example in 
this, that we can clearly apprehend substance apart from 
the mode which we say differs from it; while, on the 
other hand, we cannot conceive this mode without con- 
ceiving the substance itself. There is, for example, a 
modal distinction between figure or motion and corporeal 
substance in which both exist; there is a similar distinc- 
tion between affirmation or recollection and the mind. 
Of the latter kind we have an illustration in our ability 
to recognise the one of two modes apart from the other, 
as figure apart from motion, and motion apart from 
figure; though we cannot think of either the one or the 
other without thinking of the common substance in which 
they adhere. If, for example, a stone is moved, and is 
withal square, we can, indeed, conceive its square figure 
without its motion, and reciprocally its motion without 
its square figure; but we can conceive neither this motion 
nor this figure apart from the substance of the stone. 
As for the distinction according to which the mode of one 

190 The Principles of Philosophy 

substance is different from another substance, or from 
the mode of another substance, as the motion of one body 
is different from another body or from the mind, or as 
motion is different from doubt, it seems to me that it 
should be called real rather than modal, because these 
modes cannot be clearly conceived apart from the really 
distinct substances of which they are the modes. 

LXII. Of the distinction of reason (logical distinc- 

Finally, the distinction of reason is that between a sub- 
stance and some one of its attributes, without which it is 
impossible, however, we can have a distinct conception of 
the substance itself; or between two such attributes of a 
common substance, the one of which we essay to think 
without the other. This distinction is manifest from our 
inability to form a clear and distinct idea of such substance 
if we separate from it such attribute; or to have a clear 
perception of the one of two such attributes if we separate 
it from the other. For example, because any substance 
which ceases to endure ceases also to exist, duration is not 
distinct from substances except in thought (ratione); and 
in general all the modes of thinking which we consider as 
in objects differ only in thought, as well from the objects 
of which they are thought as from each other in a common 
object.^ It occurs, indeed, to me that I have elsewhere 
classed this kind of distinction with the modal (viz., 
towards the end of the Reply to the First Objections to 
the Meditations on the First Philosophy); but there it 
was only necessary to treat of these distinctions generally, 
and it was sufficient for my purpose at that time simply 
to distinguish both of them from the real. 

LXIII. How thought and extension may be distinctly 
known, as constituting, the one the nature of mind, the 
other that of body. 

Thought and extension may be regarded as constituting 
the natures of intelligent and corporeal substance; and 

^ " and generally all the attributes that lead us to entertain 
different thoughts of the same thing, such as, for example, the 
extension of body and its property of divisibility, do not differ 
from the body which is to us the object of them, or from each other, 
unless as we sometimes confusedly think the one without thinking 
the other." — French, 

Human Knowledge loi 

then they must not be otherwise conceived than as the 
thinking and extended substances themselves, that is, as 
mind and body, which in this way are conceived with the 
greatest clearness and distinctness. Moreover, we more 
easily conceive extended or thinking substance' than sub- 
stance by itself, or with the omission of its thinking or 
extension. For there is some difficulty in abstracting the 
notion of substance from the notions of thinking and 
extension, which, in truth, are only diverse in thought 
itself {i.e., logically different); and a concept is not more 
distinct because it comprehends fewer properties, but 
because we accurately distinguish what is comprehended 
in it from all other notions. 

LXIV. How these may likewise be distinctly conceived 
as modes of substance. 

Thought and extension may be also considered as modes 
of substance; in as far, namely, as the same mind may 
have many different thoughts, and the same body, with its 
size unchanged, may be extended in several diverse ways, 
at one time more in length and less in breadth or depth, 
and at another time more in breadth and less in length ; 
and then they are modally distinguished from substance, 
and can be conceived not less clearly and distinctly, pro- 
vided they be not regarded as substances or things 
separated from others, but simply as modes of things. 
For by regarding them as in the substances of which 
they are the modes, we distinguish them from these 
substances, and take them for what in truth they are: 
whereas, on the other hand, if we wish to consider them 
apart from the substances in which they are, we should 
by this itself regard them as self-subsisting things, and 
thus confound the ideas of mode and substance. 

LXV. How we may likewise know their modes. 

In the same way we will best apprehend the diverse 
modes of thought, as intellection, imagination, recollection, 
volition, etc., and also the diverse modes of extension, 
or those that belong to extension, as all figures, the situa- 
tion of parts and their motions, provided we consider them 
simply as modes of the things in which they are; and 
motion as far as it is concerned, provided we think merely 
of locomotion, without seeking to know the force that 

1 92 The Principles of Philosophy 

produces it, and which nevertheless I will essay to explain 
in its own place. 

LXVI. How our sensations, affections, and appetites 
may be clearly known, although we are frequently wrong 
in our judgments regarding them. 

There remain our sensations, affections, and appetites, 
of which we may also have a clear knowledge, if we take 
care to comprehend in the judgments we form of them 
only that which is precisely contained in our perception of 
them, and of which we are immediately conscious. There 
is, however, great difficulty in observing this, at least in 
respect of sensations; because we have all, without excep- 
tion, from our youth judged that all the things we per- 
ceived by our senses had an existence beyond our thought, 
and that they were entirely similar to the sensations, that 
is, perceptions, we had of them. Thus when, for example, 
we saw a certain colour, we thought we saw something 
occupying a place out of us, and which was entirely 
similar to that idea of colour we were then conscious of; 
and from the habit of judging in this way, we seemed to 
see this so clearly and distinctly that we esteemed 
it {i.e., the externality of the colour) certain and in- 

LXVII. That we are frequently deceived in our judg- 
ments regarding pain itself. 

The same prejudice has place in all our other sensations, 
even in those of titillation and pain. For though we are 
not in the habit of believing that there exist out of us 
objects that resemble titillation and pain, we do not never- 
theless consider these sensations as in the mind alone, or 
in our perception, but as in the hand, or foot, or some 
other part of our body. There is no reason, however, to 
constrain us to believe that the pain, for example, which 
we feel, as it were, in the foot is something out of the mind 
existing in the foot, or that the light which we see, as it 
were, in the sun exists in the sun as it is in us. Both 
these beliefs are prejudices of our early years, as will 
clearly appear in the sequel. 

LXVIII. How in these things what we clearly conceive 
is to be distinguished from that in which we may be 

Human Knowledge lo^ 

^ But that we may distinguish what is clear in our sensa- 
tions from what is obscure, we ought most carefully to 
observe that we possess a clear and distinct knowled^re of 
pam, colour, and other things of this sort, when we'^con- 
sider them simply as sensations or thoughts; but that 
when they are judged to be certain things subsisting 
beyond our mind, we are wholly unable to form any con"^ 
ception of them. Indeed, when any one tells us that he 
sees colour in a body or feels pain in one of his limbs, this 
is exactly the same as if he said that he there saw or felt 
something of the nature of which he was entirely ignorant, 
or that he did not know what he saw or felt. For althou^^h' 
when less attentively examining his thoughts, a person 
may easily persuade himself that he has some knowledge 
of it, since he supposes that there is something resembling 
that sensation of colour or of pain of which he is conscious ; 
yet, if he reflects on what the sensation of colour or pain 
represents to him as existing in a coloured body or in a 
wounded member, he will find that of such he has abso- 
lutely no knowledge. 

LXIX. That magnitude, figure, etc., are known far 
differently from colour, pain, etc. 

What we have said above will be more manifest, espe- 
cially if we consider that size in the body perceived, figure, 
motion (at least local, for philosophers by fancying other 
kinds of motion have rendered its nature less intelligible 
to themselves), the situation of parts, duration, number, 
and those other properties which, as we have already said, 
we clearly perceive in all bodies, are known by us in a 
way altogether different from that in which we know what 
colour is in the same body, or pain, smell, taste, or any 
other of those properties which I have said above must be 
referred to the senses. For although when we see a body 
we are not less assured of its existence from its appearing 
figured than from its appearing coloured,^ we yet know 
with far greater clearness its property of figure than its 

LXX. That we may judge of sensible things in two 
ways, by the one of which we avoid error, by the other 
fall into it. 

^ ** by the colour we perceive an occasion of it." — French. 


1 94 The Principles of Philosophy- 
It is thus manifest that to say we perceive colours in 
objects is in reahty equivalent to saying we perceive some- 
thing in objects and are yet ignorant of what it is, except 
as that which determines in us a certain highly vivid and 
clear sensation, which we call the sensation of colours. 
There is, however, very great diversity in the manner of 
judging: for so long as we simply judge that there is an 
unknown something in objects (that is, in things such as 
they are, from which the sensation reached us), so far are 
we from falling into error that, on the contrary, we thus 
rather provide against it, for we are less apt to judge 
rashly of a thing which we observe we do not know. But 
when we think we perceive colours in objects, although 
we are in reality ignorant of what we then denominate 
colour, and are unable to conceive any resemblance 
between the colour we suppose to be in objects, and that 
of which we are conscious in sensation, yet because we 
do not observe this, or because there are in objects several 
properties, as size, figure, number, etc., which, as we 
clearly know, exist, or may exist in them as they are 
perceived by our senses or conceived by our understand- 
ing, we easily glide into the error of holding that what is 
called colour in objects is something entirely resembling 
the colour we perceive, and thereafter of supposing that 
we have a clear perception of what is in no way perceived 
by us. 

LXXI. That the chief cause of our errors is to be found 
in the prejudices of our childhood. 

And here we may notice the first and chief cause of our 
errors. In early life the mind was so closely bound to the 
body that it attended to nothing beyond the thoughts by 
which it perceived the objects that made impression on the 
body: nor as yet did it refer these thoughts to anything 
existing beyond itself, but simply felt pain when the body 
was hurt, or pleasure when anything beneficial to the body 
occurred, or if the body was so slightly affected that it was 
neither greatly benefited nor hurt, the mind experienced 
the sensations we call tastes, smells, sounds, heat, cold, 
light, colours, and the like, which in truth are representa- 
tive of nothing existing out of our mind, and which vary 
according to the diversities of the parts and modes in 

Human Knowledge lor 

which the body is affected.i The mind at the same time 
also perceived magnitudes, figures, motions, and the Hke 
which were not presented to it as sensations but as things 
of the modes of things existing, or at least capable of 
existing out of thought, although it did not yet observe 
this difference between these two kinds of perceptions. 
And afterwards when the machine of the body, which has 
been so fabricated by nature that it can of its own inherent 
power move itself in various ways, by turning itself at 
random on every side, followed after what was useful and 
avoided what was detrimental; the mind, which was 
closely connected with it, reflecting on the objects it 
pursued or avoided, remarked, for the first time, that they 
existed out of itself, and not only attributed to them 
magnitudes, figures, motions, and the like, which it appre- 
hended either as things or as the modes of things, but, 
in addition, attributed to them tastes, odours, and the 
other ideas of that sort, the sensations of which were 
caused by itself; ^ and as it only considered other objects 
in so far as they were useful to the body, in which it was 
immersed, it judged that there was greater or less reality 
in each object, according as the impressions it caused on 
the body were more or less powerful. Hence arose the 
belief that there was more substance or body in rocks 
and metals than in air or water, because the mind per- 
ceived in them more hardness and weight. Moreover, 
the air was thought to be merely nothing so long as we 
experienced no agitation of it by the wind, or did not feel 
it hot or cold. And because the stars gave hardly more 
light than the slender flames of candles, we supposed that 
each star was but of this size. Again, since the mind did 
not observe that the earth moved on its axis, or that its 
^Superficies was curved like that of a globe, it was on that 
account more ready to judge the earth immovable and 
its surface flat. And our mind has been imbued from our 
infancy with a thousand other prejudices of the same sort, 
which afterwards in our youth we forgot we had accepted 

^ " which vary according to the diversities of the movements 
that pass from all parts ot our body to the part of the brain to 
which it (the mind) is closely joined and united." — French. 

* " which it perceived on occasion of them " {i.e., of external 
objects) . — French, 

196 The Principles of Philosophy 

without sufficient examination, and admitted as possessed 
of the highest truth and clearness, as if they had been 
known by means of our senses, or implanted in us by 

LXXII. That the second cause of our errors is that we 
cannot forget these prejudices. 

And although now in our mature years, when the mind, 
being no longer wholly subject to the body, is not in the 
habit of referring all things to it, but also seeks to discover 
the truth of things considered in themselves, we observe 
the falsehood of a great many of the judgments we had 
before formed; yet we experience a difficulty in expung- 
ing them from our memory, and, so long as they remain 
there, they give rise to various errors. Thus, for example, 
since from our earliest years we imagined the stars to be 
of very small size, we find it highly difficult to rid our- 
selves of this imagination, although assured by plain 
astronomical reasons that they are of the greatest, — so 
prevailing is the power of preconceived opinion. 

LXXIII. The third cause is, that we become fatigued 
by attending to those objects which are not present to the 
senses; and that we are thus accustomed to judge of these 
not from present perception but from preconceived 

Besides, our mind cannot attend to any object without 
at length experiencing some pain and fatigue; and of all 
objects it has the greatest difficulty in attending to those 
which are present neither to the senses nor to the imagina- 
tion : whether for the reason that this is natural to it from 
its union with the body, or because in our early years, 
being occupied merely with perceptions and imaginations, 
it has become more familiar with, and acquired greater 
facility in thinking in those modes than in any other. 
Hence it also happens that many are unable to conceive 
any substance except what is imaginable and corporeal, 
and even sensible. For they are ignorant of the circum- 
stance that those objects alone are imaginable which 
consist in extension, motion, and figure, while there are 
many others besides these that are intelligible; and they 
persuade themselves that nothing can subsist but body, 
and, finally, that there is no body which is not sensible. 

Human Knowledge 197 

And since in truth we perceive no object such as it is by 
sense alone [but only by our reason exercised upon sensible 
objects], as will hereafter be clearly shown, it thus happens 
that the majority during life perceive nothing unless in a 
confused way. 

LXXIV. The fourth source of our errors is, that we 
attach our thoughts to words which do not express them 
with accuracy. 

Finally, since for the use of speech we attach all our 
conceptions to words by which to express them, and com- 
mit to memory our thoughts in connection with these 
terms, and as we afterwards find it more easy to recall the 
words than the things signified by them, we can scarcely 
conceive anything with such distinctness as to separate 
entirely what we conceive from the words that were 
selected to express it. On this account the majority 
attend to words rather than to things; and thus very 
frequently assent to terms without attachmg to them any 
meaning, either because they think they once understood 
them, or imagine they received them from others by whom 
they were correctly understood. This, however, is not the 
place to treat of this matter in detail, seeing the nature 
of the human body has not yet been expounded, nor the 
existence even of body established ; enough, nevertheless, 
appears to have been said to enable one to distinguish 
such of our conceptions as are clear and distinct from those 
that are obscure and confused. 

LXXV. Summary of what must be observed in order 
to philosophise correctly. 

Wherefore if we would philosophise in earnest, and give 
/Ourselves to the search after all the truths we are capable of 
'knowing, we must, in the first place, lay aside our preju- 
dices; in other words, we must take care scrupulously to 
withhold our assent from the opinions we have formerly 
admitted, until upon new examination we discover that 
they are true. We must, in the next place, make an 
orderly review of the notions we have in our minds, and 
hold as true all and only those which we will clearly and 
distinctly apprehend. In this way we will observe, first 
of all, that we exist in so far as it is our nature to think, 
and at the same time that there is a God upon whom we 

198 The Principles of Philosophy 

depend; and after considering his attributes we will be 
able to investigate the truth of all other things, since God 
is the cause of them. Besides the notions we have of God 
and of our mind, we will likewise find that we possess the 
knowledge of many propositions which are eternally true, 
as, for example, that nothing cannot be the cause of any- 
thing, etc. We will farther discover in our minds the 
knowledge of a corporeal or extended nature that may be 
moved, divided, etc., and also of certain sensations that 
affect us, as of pain, colours, tastes- etc., although we do 
not yet know the cause of our being so affected; and, 
comparing what we have now learned, by examining 
those things in their order, with our former confused 
knowledge of them, we will acquire the habit of forming 
clear and distinct conceptions of all the objects we are 
capable of knowing. In these few precepts seem to me to 
be comprised the most general and important principles 
of human knowledge. 

LXXVI. That we ought to prefer the Divine authority 
to our perception : ^ but that, apart from things revealed, 
we ought to assent to nothing that we do not clearly 

Above all, we must impress on our memory the infal- 
lible rule, that what God has revealed is incomparably 
more certain than anything else; and that we ought to 
submit our belief to the Divine authority rather than to 
our own judgment, even although perhaps the light of 
reason should, with the greatest clearness and evidence, 
appear to suggest to us something contrary to what is 
revealed. But in things regarding which there is no 
revelation, it is by no means consistent with the character 
of a philosopher to accept as true what he has not ascer- 
tained to be such, and to trust more to the senses, in other 
words, to the inconsiderate judgments of childhood than 
to the dictates of mature reason. 

^ ** reasonings." — French, 



I. The grounds on which the existence of material 
things may be known with certainty. 

Although we are all sufficiently persuaded of the exist- 
ence of material things, yet, since this was before called 
in question by us, and since we reckoned the persuasion of 
their existence as among the prejudices of our childhood, 
it is now necessary for us to investigate the grounds on 
which this truth may be known with certainty. In the 
first place, then, it cannot be doubted that every percep- 
tion we have comes to us from some object different from 
our mind; for it is not in our power to cause ourselves to 
experience one perception rather than another, the per- 
ception being entirely dependent on the object which 
affects our senses. It may, indeed, be matter of inquiry 
whether that object be God, or something different from 
God; but because we perceive, or rather, stimulated by 
sense, clearly and distinctly apprehend, certain matter 
extended in length, breadth, and thickness, the various 
parts of which have different figures and motions, and 
give rise to the sensations we have of colours, smells, 
pain, etc., God would, without question, deserve to be 
regarded as a deceiver, if he directly and of himself pre- 
sented to our mind the idea of this extended matter, or 
merely caused it to be presented to us by some object 
which possessed neither extension, figure, nor motion. 
For we clearly conceive this matter as entirely distinct 
from God, and from ourselves, or our mind; and appear 
even clearly to discern that the idea of it is formed in us 
on occasion of objects existing out of our minds, to which 
it is in every respect similar. But since God cannot 
deceive us, for this is repugnant to his nature, as has been 
already remarked, we must unhesitatingly conclude that 
there exists a certain object extended in length, breadth, 


200 The Principles of Philosophy 

and thickness, and possessing all those properties which 
we clearly apprehend to belong to what is extended. 
And this extended substance is what we call body or 

II. How we likewise know that the human body is closely 
connected with the mind. 

We ought also to conclude that a certain body is more 
closely united to our mind than any other, because we 
clearly observe that pain and other sensations affect us 
without our foreseeing them; and these, the mind is 
conscious, do not arise from itself alone, nor pertain to 
it, in so far as it is a thing which thinks, but only in 
so far as it is united to another thing extended and 
movable, which is called the human body. But this is 
not the place to treat in detail of this matter. 

III. That the perceptions of the senses do not teach us 
what is in reality in things, but what is beneficial or 
hurtful to the composite whole of mind and body. 

It will be sufficient to remark that the perceptions of 
the senses are merely to be referred to this intimate union 
of the human body and mind, and that they usually make 
us aware of what, in external objects, may be useful or 
adverse to this union, but do not present to us these 
objects as they are in themselves, unless occasionally and 
by accident. For, after this observation, we will without 
difficulty lay aside the prejudices of the senses, and will 
have recourse to our understanding alone on this question, 
by reflecting carefully on the ideas implanted in it by 

IV. That the nature of body consists not in weight, 
hardness, colour, and the like, but in extension alone. 

In this way we will discern that the nature of matter or 
body, considered in general, does not consist in its being 
hard, or ponderous, or coloured, or that which affects our 
senses in any other way, but simply in its being a sub- 
stance extended in length, breadth, and depth. For, with 
respect to hardness, we know nothing of it by sense farther 
than that the parts of hard bodies resist the motion of our 
hands on coming into contact with them; but if every 
time our hands moved towards any part, all the bodies 
in that place receded as quickly as our hands approached, 

Material Things 201 

we should never feel hardness; and yet we have no reason 
to believe that bodies which might thus recede would on 
this account lose that which makes them bodies. The 
nature of body does not, therefore, consist in hardness. 
In the same way, it may be shown that weight, colour, 
and all the other quaHties of this sort, which are perceived 
in corporeal matter, may be taken from it, itself mean- 
while remaining entire: it thus follows that the nature of 
body depends on none of these. 

V. That the truth regarding the nature of body is 
obscured by the opinions respecting rarefaction and a 
vacuum with which we are pre-occupied. 

There still remain two causes to prevent its being fully 
admitted that the true nature of body consists in exten- 
sion alone. The first is the prevalent opinion, that most 
bodies admit of being so rarefied and condensed that, 
when rarefied, they have greater extension than when 
condensed; and some even have subtilised to such a 
degree as to make a distinction between the substance of 
body and its quantity, and between quantity itself and 
extension. The second cause is this, that where we 
conceive only extension in length, breadth, and depth, 
we are not in the habit of saying that body is there, but 
only space and further void space, which the generality 
believe to be a mere negation. 

VI. In wkat way rarefaction takes place. 

But with regard to rarefaction and condensation, who- 
ever gives his attention to his own thoughts, and admits 
nothing of which he is not clearly conscious, will not 
suppose that there is anything in those processes further 
than a change of figure in the body rarefied or condensed: 
so that, in other words, rare bodies are those between the 
parts of which there are numerous distances filled with 
other bodies; and dense bodies, on the other hand, those 
whose parts approaching each other, either diminish these 
distances or take them wholly away, in the latter of which 
cases the body is rendered absolutely dense. The body, 
however, when condensed, has not, therefore, less exten- 
sion than when the parts embrace a greater space, owing 
to their removal from each other, and their dispersion mto 
branches. For we ought not to attribute to it the exten- 

202 The Principles of Philosophy 

sion of the pores or distances which its parts do not occupy 
when it is rarefied, but to the other bodies that fill these 
interstices; just as when we see a sponge full of water or 
any other liquid, we do not suppose that each part of the 
sponge has on this account greater extension than when 
compressed and dry, but only that its pores are wider, and 
therefore that the body is diffused over a larger space. 

VII. That rarefaction cannot be intelligibly explained 
unless in the way here proposed. 

And indeed I am unable to discover the force of the 
reasons which have induced some to say that rarefaction 
is the result of the augmentation of the quantity of body, 
rather than to explain it on the principle exemplified in 
the case of a sponge. For although when air or water are 
rarefied we do not see any of the pores that are rendered 
large, or the new body that is added to occupy them, it is 
yet less agreeable to reason to suppose something that is 
unintelligible for the purpose of giving a verbal and merely 
apparent explanation of the rarefaction of bodies, than 
to conclude, because of their rarefaction, that there are 
pores or distances between the parts which are increased 
in size, and filled with some new body. Nor ought we to 
refrain from assenting to this explanation, because we 
perceive this new body by none of our senses, for there is 
no reason which obliges us to believe that we should per- 
ceive by our senses all the bodies in existence. And we 
see that it is very easy to explain rarefaction in this manner^ 
but impossible in any other; for, in fine, there would be, 
as appears to me, a manifest contradiction in supposing 
that any body was increased by a quantity or extension 
which it had not before, without the addition to it of a 
new extended substance, in other words, of another body^ 
because it is impossible to conceive any addition of exten- 
sion or quantity to a thing without supposing the addition 
of a substance having quantity or extension, as will more 
clearly appear from what follows. 

VIII. That quantity and number differ only in thought 
(rattone) from that which has quantity and is numbered. 

For quantity differs from extended substance, and 
number from what is numbered, not in reality but merely 
in our thought; so that, for example, we may consider the 

Material Things 203 

whole nature of a corporeal substance which is comprised 
in a space of ten feet, although we do not attend to this 
measure of ten feet, for the obvious reason that the thing 
conceived is of the same nature in any part of that space 
as in the whole; and, on the other hand, we can conceive 
the number ten, as also a continuous quantity of ten feet 
without thinking of this determinate substance, because 
the concept of the number ten is manifestly the same 
whether we consider a number of ten feet or ten of any- 
thing else ; and we can conceive a continuous quantity of 
ten feet without thinking of this or that determinate 
substance, although we cannot conceive it without some 
extended substance of which it is the quantity. It is in 
reality, however, impossible that any, even the least part, 
of such quantity or extension, can be taken away, without 
the retrenchment at the same time of as much of the 
substance, nor, on the other hand, can we lessen the sub- 
stance, without at the same time taking as much from the 
quantity or extension. 

IX. That corporeal substance, when distinguished from 
its quantity, is confusedly conceived as something in- 

Although perhaps some express themselves otherwise 
on this matter, I am nevertheless convinced that they 
do not think differently from what I have now said: for 
when they distinguish (corporeal) substance from exten- 
sion or quantity, they either mean nothing by the word 
(corporeal) substance, or they form in their minds merely 
a confused idea of incorporeal substance, which they 
falsely attribute to corporeal, and leave to extension the 
true idea of this corporeal substance; which extension 
they call an accident, but with such impropriety as to 
make it easy to discover that their words are not in 
harmony with their thoughts. 

X. What space or internal place is. 

Space or internal place, and the corporeal substance 
which is comprised in it, are not different in reality, but 
merely in the mode in which they are wont to be conceived 
by us. For, in truth, the same extension in lengthy 
breadth, and depth, which constitutes space, constitutes 
body; and the difference between them lies only in this. 

204 The Principles of Philosophy 

that in body we consider extension as particular^ and con- 
ceive it to change with the body; whereas in space we 
attribute to extension a generic unity, so that after taking 
from a certain space the body which occupied it, we do 
not suppose that we have at the same time removed the 
extension of the space, because it appears to us that the 
same extension remains there so long as it is of the same 
magnitude and figure, and preserves the same situation 
in respect to certain bodies around it, by means of which 
we determine this space. 

XI. How space is not in reality different from corporeal 

And indeed it will be easy to discern that it is the same 
extension which constitutes the nature of body as of space, 
and that these two things are mutually diverse only as the 
nature of the genus and species differs from that of the 
individual, provided we reflect on the idea we have of any 
body, taking a stone for example, and reject all that is 
not essential to the nature of body. In the first place, 
then, hardness may be rejected, because if the stone were 
liquefied or reduced to powder, it would no longer possess 
hardness, and yet would not cease to be a body; colour 
also may be thrown cut of account, because we have fre- 
quently seen stones so transparent as to have no colour; 
again, we may reject weight, because we have the case of 
fire, which, though very light, is still a body; and, finally, 
we may reject cold, heat, and all the other qualities of 
this sort, either because they are not considered as in the 
stone, or because, with the change of these qualities, the 
stone is not supposed to have lost the nature of body. 
After this examination we will find that nothing remains 
in the idea of body, except that it is something extended in 
length, breadth, and depth; and this something is com- 
prised in our idea of space, not only of that which is full 
of body, but even of what is called void space. 

XII. How space differs from body in our mode of con- 
ceiving it. 

There is, however, some difference between them in 
the mode of conception; for if we remove a stone from 
the space or place in which it was, we conceive that its 
extension also is taken away, because we regard this as 

Material Things 205 

particular, and inseparable from the stone itself: but 
meanwhile we suppose that the same extension of place 
in which this stone was remains, although the place of the 
stone be occupied by wood, water, air, or by any other 
body, or be even supposed vacant, because we now con- 
sider extension in general, and think that the same is 
common to stones, wood, water, air, and other bodies, 
and even to a vacuum itself, if there is any such thing, 
provided it be of the same magnitude and figure as before, 
and preserve the same situation among the external bodies 
which determine this space. 
XIII. What external place is. 

The reason of which is, that the words place and space 
signify nothing really different from body which is said to 
be in place, but merely designate its magnitude, figure, 
and situation among other bodies. For it is necessary, in 
order to determine this situation, to regard certain other 
bodies which we consider as immovable; and, according 
as we look to different bodies, we may see that the same 
thing at the same time does and does not change place. 
For example, when a vessel is being carried out to sea, a 
person sitting at the stern may be said to remain always 
in one place, if we look to the parts of the vessel, since with 
respect to these he preserves the same situation; and on 
the other hand, if regard be had to the neighbouring 
shores, the same person will seem to be perpetually chang- 
ing place, seeing he is constantly receding from one shore 
and approaching another. And besides, if we suppose 
that the earth moves, and that it makes precisely as much 
way from west to east as the vessel from east to west, we 
will again say that the person at the stern does not change 
his place, because this place will be determined by certain 
immovable points which we imagine to be in the heavens. 
But if at length we are persuaded that there are no points 
really immovable in the universe, as will hereafter be 
shown to be probable, we will thence conclude that nothing 
has a permanent place unless in so far as it is fixed by our 

XIV. Wherein place and space differ. 
The terms place and space, however, differ in significa- 
tion, because place more expressly designates situation 

2o6 The Principles of Philosophy 

than magnitude or figure, while, on the other hand, we 
think of the latter when we speak of space. For we 
frequently say that a thing succeeds to the place of another 
although it be not exactly of the same magnitude or 
figure; but we do not therefore admit that it occupies 
the same space as the other; and when the situation is 
changed we say that the place also is changed, although 
there are the same magnitude and figure as before : so that 
when we say that a thing is in a particular place, we mean 
merely that it is situated in a determinate way in respect 
of certain other objects; and when we add that it occupies 
such a space or place we understand besides that it is of 
such determinate magnitude and figure as exactly to fill 
this space. 

XV. How external place is rightly taken for the super- 
ficies of the surrounding body. 

And thus we never indeed distinguish space from ex- 
tension in length, breadth, and depth; we sometimes, 
however, consider place as in the thing placed, and at 
other times as out of it. Internal place indeed differs 
in no way from space; but external place may be taken 
for the superficies that immediately surrounds the thing 
placed. It ought to be remarked that by superficies we 
do not here understand any part of the surrounding body, 
but only the boundary between the surrounding and sur- 
rounded bodies, which is nothing more than a mode; or 
at least that we speak of superficies in general which is no 
part of one body rather than another, but is always con- 
sidered the same, provided it retain the same magnitude 
and figure. For although the whole surrounding body 
with its superficies were changed, it would not be supposed 
that the body which was surrounded by it had therefore 
changed its place, if it meanwhile preserved the same 
situation with respect to the other bodies that are regarded 
as immovable. Thus, if we suppose that a boat is cairied 
in one direction by the current of a stream, and impelled 
by the wind in the opposite with an equal force, so that 
its situation with respect to the banks is not changed, we 
will readily admit that it remains in the same place, 
although the whole superficies which surrounds it is 
incessantly changing. 

Material Things 207 

XVI. That a vacuum or space in which there is abso- 
lutely no body is repugnant to reason. 

With regard to a vacuum, in the philosophical sense of 
the term, that is, a space in which there is no substance 
it IS evident that such does not exist, seeing the extension 
of space or internal place is not different from that of body 
For since from this alone, that a body has extension in 
length, breadth, and depth, we have reason to conclude 
that it is a substance, it being absolutely contradictory 
that nothing should possess extension, we ought to form 
a similar inference regarding the space which is supposed 
void, viz., that since there is extension in it there is 
necessarily also substance. 

XVII. That a vacuum in the ordinary use of the term 
does not exclude all body. 

And, in truth, by the term vacuum in its common use, 
we do not mean a place or space in which there is abso- 
lutely nothing, but only a place in which there is none 
of those things we presume ought to be there. Thus, 
because a pitcher is made to hold water, it is said to be 
empty when it is merely filled with air; or if there are no 
fish in a fish-pond, we say there is nothing in it, although 
it be full of water; thus a vessel is said to be empty, when, 
in place of the merchandise which it was designed to 
carry, it is loaded with sand only, to enable it to resist 
the violence of the wind; and, finally, it is in the same 
sense that we say space is void when it contains nothing 
sensible, although it contain created and self-subsisting 
matter; for we are not in the habit of considering the 
bodies near us, unless in so far as they cause in our organs 
of sense impressions strong enough to enable us to perceive 
them. And if, in place of keeping in mind what ought 
to be understood by these terms a vacuum and nothing, 
we afterwards suppose that in the space we called a 
vacuum, there is not only no sensible object, but no 
object at all, we will fall into the same error as if, because 
a pitcher in which there is nothing but air, is, in common 
speech, said to be empty, we were therefore to judge that 
the air contained in it is not a substance (res subsistens), 

XVIII. How the prejudice of an absolute vacuum is to 
be corrected. 

2o8 The Principles of Philosophy 

We have almost all fallen into this error from the 
earliest age, for, observing that there is no necessary 
connection between a vessel and the body it contains, we 
thought that God at least could take from a vessel the 
body which occupied it, without it being necessary that 
any other should be put in the place of the one removed. 
But that we may be able now to correct this false opinion, 
it is necessary to remark that there is in truth no con- 
nection between the vessel and the particular body which 
it contains, but that there is an absolutely necessary 
connection between the concave figure of the vessel and 
the extension considered generally which must be com- 
prised in this cavity; so that it is not more contradictory 
to conceive a mountain without a valley than such a 
cavity without the extension it contains, or this extension 
apart from an extended substance, for, as we have often 
said, of nothing there can be no extension. And accord- 
ingly, if it be asked what would happen were God to 
remove from a vessel all the body contained in it, without 
permitting another body to occupy its place, the answer 
must be that the sides of the vessel would thus come into 
proximity with each other. For two bodies must touch 
each other when there is nothing between them, and it 
is manifestly contradictory for two bodies to be apart, 
in other words, that there should be a distance between 
them, and this distance yet be nothing; for all distance 
is a mode of extension, and cannot therefore exist without 
an extended substance. 

XIX. That this confirms what was said of rarefaction. 

After we have thus remarked that the nature of cor- 
poreal substance consists only in its being an extended 
thing, and that its extension is not different from that 
which we attribute to space, however empty, it is easy to 
discover the impossibility of any one of its parts in any 
way whatsoever occupying more space at one time than 
at another, and thus of being otherwise rarefied than in 
the way explained above; and it is easy to perceive also 
that there cannot be more matter or body in a vessel 
when it is filled with lead or gold, or any other body how- 
ever heavy and hard, than when it but contains air and 
is supposed to be empty: for the quantity of the parts 

Material Things 209 

of which a body is composed does not depend on their 
weight or hardness, but only on the extension, which is 
always equal in the same vase. 

XX. That from this the non-existence of atoms may 
likewise be demonstrated. 

We likewise discover that there cannot exist any atoms 
or parts of matter that are of their own nature indivisible. 
For however small we suppose these parts to be, yet 
because they are necessarily extended, we are always able 
in thought to divide any one of them into two or more 
smaller parts, and may accordingly admit their divisi- 
bility. For there is nothing we can divide in thought 
which we do not thereby recognise to be divisible; and, 
therefore, were we to judge it indivisible our judgment 
would not be in harmony with the knowledge we have of 
the thing; and although we should even suppose that 
God had reduced any particle of matter to a smallness so 
extreme that it did not admit of being further divided, 
it would nevertheless be improperly styled indivisible, 
for though God had rendered the particle so small that it 
was not in the power of any creature to divide it, he 
could not however deprive himself of the ability to do so, 
since it is absolutely impossible for him to lessen his own 
omnipotence, as was before observed. Wherefore, abso- 
lutely speaking, the smallest extended particle is always 
divisible, since it is such of its very nature. 

XXI. It is thus also demonstrated that the extension 
of the world is indefinite. 

We further discover that this world or the whole 
(universitas) of corporeal substance, is extended without 
limit, for wherever we fix a limit, we still not only imagine 
beyond it spaces indefinitely extended, but perceive these 
to be truly imaginable, in other words, to be in reality such 
as we imagine them; so that they contain in them cor- 
poreal substance indefinitely extended, for, as has been 
already shown at length, the idea of extension which we 
conceive in any space whatever is plainly identical with 
the idea of corporeal substance. 

XXII. It also follows that the matter of the heavens 
and earth is the same, and that there cannot be a plurality 

of worlds. 


2 1 o The Principles of Philosophy 

And it may also be easily inferred from all this that the 
earth and heavens are made of the same matter; and that 
even although there were an infinity of worlds, they would 
all be composed of this matter; from which it follows that 
a plurality of worlds is impossible, because we clearly 
conceive that the matter whose nature consists only in its 
being an extended substance, already wholly occupies all 
the imaginable spaces where these other worlds could alone 
be, and we cannot find in ourselves the idea of any other 

XXIII. That all the variety of matter, or the diversity 
of its forms, depends on motion. 

There is therefore but one kind of matter in the whole i 
universe, and this we know only by its being extended. 
All the properties we distinctly perceive to belong to it 
are reducible to its capacity of being divided and moved 
according to its parts; and accordingly it is capable of 
all those affections which we perceive can arise from 
the motion of its parts. For the partition of matter in 
thought makes no change in it; but all variation of it, 
or diversity of form, depends on motion. The philo- 
sophers even seem universally to have observed this, for 
they said that nature was the principle of motion and 
rest, and by nature they understood that by which all 
corporeal things become such as they are found in 

XXIV. What motion is, taking the term in its common 

But motion (viz., local, for I can conceive no other kind 
of motion, and therefore I do not think we ought to sup- 
pose there is any other in nature), in the ordinary sense 
of the term, is nothing more than the action by which a 
body passes from one place to another. And just as we 
have remarked above that the same thing may be said 
to change and not to change place at the same time, so 
also we may say that the same thing is at the same time 
moved and not moved. Thus, for example, a person 
seated in a vessel which is setting sail, thinks he is in 
motion if he look to the shore that he has left, and con- 
sider it as fixed; but not if he regard the ship itself, 
among the parts of which he preserves always the same 

Material Things 2 1 1 

situation. Moreover, because we are accustomed to 
suppose that there is no motion without action, and that 
in rest there is the cessation of action, the person thus 
seated is more properly said to be at rest than in motion, 
seeing he is not conscious of being in action. 

XXV. What motion is properly so called. 

But if, instead of occupying ourselves with that which 
has no foundation, unless in ordinary usage, we desire to 
' know what ought to be understood by motion according 
to the truth of the thing, we may say, in order to give it a 
determinate nature, that it is the transporting of one part 
of matter or of one body from the vicinity of those bodies that 
are in immediate contact with it, or which we regard as at 
restj^ to the vicinity of other bodies. By a body as a part of 
matter, I understand all that which is transferred together, 
although it be perhaps composed of several parts, which in 
themselves have other motions; and I say that it is the 
transporting and not the force or action which transports, 
with the view of showing that motion is always in the 
movable thing, not in that which moves ; for it seems to 
me that we are not accustomed to distinguish these two 
things with sufficient accuracy. Farther, I understand 
that it is a mode of the movable thing, and not a sub- 
stance, just as figure is a property of the thing figured, and 
repose of that which is at rest. 



I. That we cannot think too highly of the works of 

Having now ascertained certain principles of material 
things, which were sought, not by the prejudices of the 
senses, but by the light of reason, and which thus possess 
so great evidence that we cannot doubt of their truth, it 
remains for us to consider whether from these alone we 
can deduce the explication of all the phenomena of nature. 
We will commence with those phenomena that are of the 
greatest generality, and upon which the others depend, 
as, for example, with the general structure of this whole 
visible world. But in order to our philosophising aright 
regarding this, two things are first of all to be observed. 
The first is, that we should ever bear in mind the infinity 
of the power and goodness of God, that we may not fear 
falling into error by imagining his works to be too great, 
beautiful, and perfect, but that we may, on the contrary, 
take care lest, by supposing limits to them of which we 
have no certain knowledge, we appear to think less highly 
than we ought of the power of God. 

II. That we ought to beware lest, in our presumption, 
we imagine that the ends which God proposed to himself 
in the creation of the world are understood by us. 

The second is, that we should beware of presuming too 
highly of ourselves, as it seems we should do if we supposed 
certain limits to the world, without being assured of their 
existence either by natural reasons or by divine revelation, 
as if the power of our thought extended beyond what God 
has in reality made; but likewise still more if we per- 
suaded ourselves that all things were created by God for us 
only, or if we merely supposed that we could comprehend 
by the power of our intellect the ends which God proposed 
to himself in creating the universe. 


The Visible World 2 1 3 

III. In what sense it may be said that all things were 
created for the sake of man. 

For although, as far as regards morals, it may be a pious 
thought to believe that God made all things for us, seeing 
we may thus be incited to greater gratitude and love 
toward him; and although it is even in some sense true, 
because there is no created thing of which we cannot make 
some use, if it be only that of exercising our mind in con- 
sidering it, and honouring God on account of it, it is yet 
by no means probable that ail things were created for us 
in this way that God had no other end in their creation; 
and this supposition would be plainly ridiculous and inept 
in physical reasoning, for we do not doubt but that many 
things exist, or formerly existed and have now ceased to 
be, which were never seen or known by man^ and were 
never of use to him.. 



I. Of what is to be borrowed from disquisitions on 
animals and man to advance the knowledge of material 

I should add nothing farther to this the fourth part of 
the Principles of Philosophy, did I purpose carrying out 
my original design of writing a fifth and sixth part, the 
one treating of things possessed of life, that is, animals 
and plants, and the other of man. But because I have 
not yet acquired sufficient knowledge of all the matters 
of which I should desire to treat in these two last parts, 
and do not know whether I ever shall have sufficient 
leisure to finish them, I will here subjoin a few things 
regarding the objects of our senses, that I may not, for 
the sake of the latter, delay too long the publication of 
the former parts, or of what may be desiderated in them, 
which I might have reserved for explanation in those 
others: for I have hitherto described this earth, and 
generally the whole visible world, as if it were merely a 
machine in which there was nothing at all to consider 
except the figures and motions of its parts, whereas our 
senses present to us many other things, for example 
colours, smells, sounds, and the like, of which, if I did not 
speak at all, it would be thought I had omitted the explica- 
tion of the majority of the objects that are in nature. 

II. What perception (sensus) is, and how we perceive. 

We must know, therefore, that although the human 
soul is united to the whole body, it has, nevertheless, its 
principal seat in the brain, where alone it not only under- 
stands and imagines, but also perceives; and this by the 
medium of the nerves, which are extended like threads 
from the brain to all the other members, with which they 
are so connected that we can hardly touch any one of 


The Earth 2 1 5 

them without moving the extremities of some of the 
nerves spread over it; and this motion passes to the 
other extremities of those nerves which are collected in 
the brain round the seat of the soul/ as I have already 
explained with sufficient minuteness in the fourth chapter 
of the Dioptrics. But the movements which are thus 
excited in the brain by the nerves, variously affect the 
soul or mmd, which is intimately conjoined with the brain, 
according to the diversity of the motions themselves! 
And the diverse affections of the mind or thoughts that 
immediately arise from these motions, are called per- 
ceptions of the senses (sensuum perceptiones)^ or, as we 
commonly speak, sensations (sensus). 

III. Of the distinction of the senses; and, first, of the 
internal, that is, of the affections of the mind (passions), 
and the natural appetites. 

The varieties of these sensations depend, firstly, on thfe 
diversity of the nerves themselves, and, secondly, of the 
movements that are made in each nerve. We have not, 
however, as many different senses as there are nerves^ 
We can distinguish but seven principal classes of nerves, 
of which two belong to the internal, and the other five to 
the external senses. The nerves which extend to the 
stomach, the oesophagus, the fauces, and the other 
internal parts that are subservient to our natural wants, 
constitute one of our internal senses. This is called the 
natural appetite (appetttiis naturalis). The other internal 
sense, which embraces all the emotions (commotiones) of 
the mind or passions, and affections, as joy, sadness, love, 
hate, and the like, depends upon the nerves which extend 
to the heart and the parts about the heart, and are ex- 
ceedingly small; for, by way of example, when the blood 
happens to be pure and well tempered, so that it dilates in 
the heart more readily and strongly than usual, this so 
enlarges and moves the small nerves scattered around the 
orifices, that there is thence a corresponding movement 
in the brain, which affects the mind with a certain natural 
feeling of joy; and as often as these same nerves are 
moved in the same way, although this is by other causes, 
they excite in our mind the same feeling {sensus, sentiment), 
1 " common sense." — French, 

2 1 6 The Principles of Philosophy 

Thus, the imagination of the enjoyment of a good does 
not contain in itself the feeling of joy, but it causes the 
animal spirits to pass from the brain to the muscles in which 
these nerves are inserted ; and thus dilating the orifices of 
the heart, it also causes these small nerves to move in the 
way appointed by nature to afford the sensation of joy. 
Thus, when we receive news, the mind first of all judges 
of it, and if the news be good, it rejoices with that intel- 
lectual joy (gaudtum intellectuale) which is independent 
of any emotion {commotio) of the body, and which the 
Stoics did not deny to their wise man [although they 
supposed him exempt from all passion]. But as soon as 
this joy passes from the understanding to the imagination, 
the spirits flow from the brain to the muscles that are 
about the heart, and there excite the motion of the small 
nerves, by means of which another motion is caused in the 
brain, which affects the mind with the sensation of animal 
joy {laetitia animalis). On the same principle, when the 
blood is so thick that it flows but sparingly into the 
ventricles of the heart, and is not there sufficiently dilated, 
it excites in the same nerves a motion quite different from 
the preceding, which, communicated to the brain, gives 
to the mind the sensation of sadness, although the mind 
itself is perhaps ignorant of the cause of its sadness. And 
all the other causes which move these nerves in the same 
way may also give to the mind the same sensation. But 
the other movements of the same nerves produce other 
effects, as the feelings of love, hate, fear, anger, etc., as far 
as they are merely affections or passions of the mind; in 
other words, as far as they are confused thoughts which 
the mind has not from itself alone, but from its being 
closely joined to the body, from which it receives impres- 
sions; for there is the widest difference between these 
passions and the distinct thoughts which we have of what 
ought to be loved, or chosen, or shunned, etc. [although 
these are often enough found together]. The natural 
appetites, as hunger, thirst, and the others, are likewise 
sensations excited in the mind by means of the nerves of 
the stomach, fauces, and other parts, and are entirely 
different from the will which we have to eat, drink [and 
to do all that which we think proper for the conservation 

The Earth 2 1 7 

of our body]; but, because this will or appetition almost 
always accompanies them, they are therefore named 

IV. Of the external senses; and first of touch. 

We commonly reckon the external senses five in number, 
because there are as many different kinds of objects which 
move the nerves and their organs, and an equal number of 
kinds of confused thoughts excited in the soul by these 
motions. In the first place, the nerves terminating in 
the skin of the whole body can be touched through this 
medium by any terrene objects whatever, and moved by 
these wholes, in one way by their hardness, in another by 
their gravity, in a third by their heat, in a fourth by their 
humidity, etc. — and in as many diverse modes as they 
are either moved or hindered from their ordinary motion, 
to that extent are diverse sensations excited in the mind, 
from which a corresponding number of tactile qualities 
derive their appellations. Besides this, when these nerves 
are moved a little more powerfully than usual, but not 
nevertheless to the degree by which our body is in any 
way hurt, there thus arises a sensation of titillation, which 
is naturally agreeable to the mind, because it testifies to 
it of the powers of the body with which it is joined [in 
that the latter can suffer the action causing this titillation, 
without being hurt]. But if this action be strong enough 
to hurt our body in any w^ay, this gives to our mind 
the sensation of pain. And we thus see why corporeal 
pleasure and paiw, although sensations of quite an opposite 
character, arise nevertheless from causes nearly alike. 

V. Of taste. 

In the second place, the other nerves scattered over the 
tongue and the parts in its vicinity are diversely moved by 
the particles of the same bodies, separated from each other 
and floating in the saliva in the mouth, and thus cause 
sensations of diverse tastes according to the diversity of 
figure in these particles.^ 

VI. Of smell. 

Thirdly, two nerves also or appendages of the bram, 
for they do not go beyond the limits of the skull, are 

Un the French this section begins, "Taste, after touch the 
grossest of the senses,** etc. 

2 1 8 The Principles of Philosophy 

moved by the particles of terrestrial bodies, separated and 
flying in the air, not indeed by all particles indifferently, 
but by those only that are sufficiently subtle and pene- 
trating to enter the pores of the bone we call the spongy, 
when drawn into the nostrils, and thus to reach the nerves. 
From the different motions of these particles arise the 
sensations of the different smells. 

VII. Of hearing. 

Fourthly, there are two nerves within the ears, so 
attached to three small bones that are mutually sustaining, 
and the first of which rests on the small membrane that 
covers the cavity we call the tympanum of the ear, that 
all the diverse vibrations which the surrounding air com- 
municates to this membrane, are transmitted to the mind 
by these nerves, and these vibrations give rise, according 
to their diversitv, to the sensations of the different sounds. 

VIII. Of sight. 

Finally, the extremities of the optic ner\^es, composing 
the coat in the eyes called the retina, are not moved by 
the air nor by any terrestrial object, but only by the 
globules of the second element,^* whence we have the sense 
of light and colours : as I have already at sufficient length 
explained in the Dioptrics and treatise of Meteors.^ 

IX. That the soul perceives only in so far as it is in 
the brain. 

It is clearly established, however, that the soul does not 
perceive in so far as it is in each member of the body, but 
only in so far as it is in the brain, where the nerves by 
their movements convey to it the diverse actions of the 
external objects that touch the parts of the body in which 
they are inserted. For, in the first place, there are various 
maladies, which, though they affect the brain alone, yet 
bring disorder upon, or deprive us altogether of the use 
of, our senses, just as sleep, which affects the brain only, 
and yet takes from us daily during a great part of our time 
the faculty of perception, which aftei*wards in our waking 
state is restored to us. The second proof is, that though 
there be no disease in the brain [or in the members in 
which the organs of the external senses are], it is never- 

1 In the French this section begins, ** Finally, sight is the most 
subtle of all the senses," etc. 

The Earth 219 

theless sufficient to take away sensation from the part of 
the body where the nerves terminate, if only the movement 
of one of the nerves that extend from the brain to these 
members be obstructed in any part of the distance that is 
between the two. And the last proof is, that we some- 
times feel pain as if in certain of our members, the cause 
of which, however, is not in these members where it is felt, 
but somewhere nearer the brain, through which the nerves 
pass that give to the mind the sensation of it. I could 
establish this fact by innumerable experiments; I will 
here, however, merely refer to one of them. A girl suffer- 
ing from a bad ulcer in the hand, had her eyes bandaged 
whenever the surgeon came to visit her, not being able 
to bear the sight of the dressing of the sore; and, the 
gangrene having spread, after the expiry of a few days the 
arm was amputated from the elbow [without the girl's 
knowledge]; linen cloths tied one above the other were 
substituted in place of the part amputated, so that she 
remained for some time without knowing that the opera- 
tion had been performed, and meanwhile she complained 
of feeling various pains, sometimes in one finger of the 
hand that was cut off, and sometimes in another. The 
only explanation of this is, that the nerves which before 
stretched downwards from the brain to the hand, and 
then terminated in the arm close to the elbow, were there 
moved in the same way as they required to be moved 
before in the hand for the purpose of impressing on the 
mind residing in the brain the sensation of pain in this or 
that finger. [And this clearly shows that the pain of the 
hand is not felt by the mind in so far as it is in the hand, 
but in so far as it is in the brain.] 

X. That the nature of the mind is such that from the 
motion alone of body the various sensations can be 
excited in it. 

In the next place, it can be proved that our mind is of 
such a nature that the motions of the body alone are suffi- 
cient to excite in it all sorts of thoughts, without it bemg 
necessary that these should in any way resemble the 
motions which give rise to them, and especially that these 
motions can excite in it those confused thoughts called 
sensations (sensus, sensationes). For we see that words, 

2 20 The Principles of Philosophy 

whether uttered by the voice or merely written, excite in 
our minds all kinds of thoughts and emotions. On the 
same paper, with the same pen and ink, by merely moving 
the point of the pen over the paper in a particular way, 
we can trace letters that will raise in the minds of our 
readers the thoughts of combats, tempests, or the furies, 
and the passions of indignation and sorrow; in place of 
which, if the pen be moved in another way hardly different 
from the former, this slight change will cause thoughts 
widely different from the above, such as those of repose, 
peace, pleasantness, and the quite opposite passions of 
love and joy. Some one will perhaps object that writing 
and speech do not immediately excite in the mind any 
passions, or imaginations of things different from the 
letters and sounds, but afford simply the knowledge of 
these, on occasion of which the mind, understanding the 
signification of the words, afterwards excites in itself the 
imaginations and passions that correspond to the words. 
But what will be said of the sensations of pain and titilla- 
tion? The motion merely of a sword cutting a part of 
our skin causes pain [but does not on that account make 
us aware of the motion or figure of the sword]. And it is 
certain that this sensation of pain is not less different from 
the motion that causes it, or from that of the part of our 
body which the sword cuts, than are the sensations we 
have of colour, sound, odour, or taste. On this ground 
we may conclude that our mind is of such a nature that 
the motions alone of certain bodies can also easily excite 
in it all the other sensations, as the motion of a sword 
excites in it the sensation of pain. 

XI. That by our senses we know nothing of external 
objects beyond their figure [or situation], magnitude, and 

Besides, we observe no such difference between the 
nerves as to lead us to judge that one set of them convey 
to the brain from the organs of the external senses any- 
thing different from another, or that anything at all 
reaches the brain besides the local motion of the nerves 
themselves. And we see that local motion alone causes 
in us not only the sensation of titillation and of pain, but 
also of light and sounds. For if we receive a blow on 


The Earth 221 

the eye of sufficient force to cause the vibration of the 
stroke to reach the retina, we see numerous sparks of fire, 
which, nevertheless, are not out of our eye; and when 
we stop our ear with our finger, we hear a humming sound, 
the cause of which can only proceed from the agitation of 
the air that is shut up within it. Finally, we frequently 
observe that heat [hardness, weight], and the other sen- 
sible qualities, as far as they are in objects, and also the 
forms of those bodies that are purely material, as, for 
example, the forms of fire, are produced in them by the 
motion of certain other bodies, and that these in their 
turn likewise produce other motions in other bodies. 
And we can easily conceive how the motion of one body 
may be caused by that of another, and diversified by the 
size, figure, and situation of its parts, but we are wholly 
unable to conceive how these same things (viz., size, 
figure, and motion) can produce something else of a 
nature entirely different from themselves, as, for example, 
those substantial forms and real qualities which many 
philosophers suppose to be in bodies; nor likewise can 
we conceive how these qualities or forms possess force to 
cause motions in other bodies. But since we know, from 
the nature of our soul, that the diverse motions of body 
are sufficient to produce in it all the sensations which it 
has, and since we learn from experience that several of 
its sensations are in reality caused by such motions, while 
we do not discover that anything besides these motions 
ever passes from the organs of the external senses to the 
brain, we have reason to conclude that we in no way 
likewise apprehend that in external objects, which we 
call light, colour, smell, taste, sound, heat or cold, and the 
other tactile qualities, or that which we call their sub- 
stantial forms, unless as the various dispositions of these 
objects which have the power of moving our nerves in 
various ways.^ 

XII. That there is no phenomenon of nature whose 
explanation has been omitted in this treatise. 

And thus it may be gathered, from an enumeration that 
is easily made, that there is no phenomenon of nature 

1 •' the diverse figures, situations, magnitudes, and motions oi 
their parts." — French. 

222 The Principles of Philosophy 

whose explanation has been omitted in this treatise; for 
beyond what is perceived by the senses, there is nothing 
that can be considered a phenomenon of nature. But 
leaving out of account motion, magnitude, figure [and the 
situation of the parts of each body], which I have ex- 
plained as they exist in body, we perceive nothing out 
of us by our senses except light, colours, smells, tastes, 
sounds, and the tactile qualities ; and these I have recently 
shown to be nothing more, at least so far as they are 
known to us, than certain dispositions of the objects, 
consisting in magnitude, figure, and motion. 

XIII. That this treatise contains no principles which 
are not universally received ; and that this philosophy is 
not new, but of all others the most ancient and common. 

But I am desirous also that it should be observed that, 
though I have here endeavoured to give an explanation of 
the whole nature of material things, I have nevertheless 
made use of no principle which was not received and 
approved by Aristotle, and by the other philosophers of 
all ages; so that this philosophy, so far from being new, 
is of all others the most ancient and common : for I have 
in truth merely considered the figure, motion, and magni- 
tude of bodies, and examined what must follow from their 
mutual concourse on the principles of mechanics, which 
are confirmed by certain and daily experience. But no 
one ever doubted that bodies are moved, and that they 
are of various sizes and figures, according to the diversity 
of which their motions also vary, and that from mutual 
collision those somewhat greater than others are divided 
into many smaller, and thus change figure. We have 
experience of the truth of this, not merely by a single 
sense, but by several, as touch, sight, and hearing: we 
also distinctly imagine and understand it. This cannot 
be said of any of the other things that fall under our 
senses, as colours, sounds, and the like; for each of these 
affects but one of our senses, and merely impresses upon 
our imagination a confused image of itself, affording our 
understanding no distinct knowledge of what it is. 

XIV. That sensible bodies are composed of insensible 

But I allow many particles in each body that are per- 

The Earth 223 

ceived by none of our senses, and this will not perhaps be 
approved of by those who take the senses for the measure 
of the knowable. [We greatly wrong human reason, 
however, as appears to me, if we suppose that it does 
not go beyond the eye-sight]; for no one can doubt that 
there are bodies so small as not to be perceptible by any 
of our senses, provided he only consider what is each 
moment added to those bodies that are being increased 
little by little, and what is taken from those that are 
diminished in the same way. A tree increases daily, and 
it is impossible to conceive how it becomes greater than 
it was before, unless we at the same time conceive that 
some body is added to it. But who ever observed by 
the senses those small bodies that are in one day added 
to a tree while growing? Among the philosophers at 
least, those who hold that quantity is indefinitely divisible, 
ought to admit that in the division the parts may become 
so small as to be wholly imperceptible. And indeed it 
ought not to be a matter of surprise that we are unable 
to perceive very minute bodies; for the nerves that must 
be moved by objects to cause perception are not them- 
selves very minute, but are like small cords, being com- 
posed of a quantity of smaller fibres, and thus the most 
minute bodies are not capable of moving them. Nor do 
I thihk that any one who makes use of his reason will 
deny that we philosophise with much greater truth when 
we judge of what takes place in those small bodies which 
are imperceptible from their minuteness only, after the 
analogy of what we see occurring in those we do perceive 
[and in this way explain all that is in nature, as I have 
essayed to do in this treatise], than when we give an 
explanation of the same things by inventing I know not 
what novelties, that have no relation to the things we 
actually perceive [as first matter, substantial forms, and 
all that grand array of qualities which many are in the 
habit of supposing, each of which it is more difllicult to 
comprehend than all that is professed to be explained by 
means of them]. 

XV. That the philosophy of Democritus is not less 
different from ours than from the common.^ 

1 *' that of Aristotle or the others."— Fmtf&. 

224 The Principles of Philosophy 

But it may be said that Democritus also supposed 
certain corpuscles that were of various figures, sizes, and 
motions, from the heaping together and mutual concourse 
of which all sensible bodies arose; and, nevertheless, his 
mode of philosophising is commonly rejected by all. To 
this I reply that the philosophy of Democritus was never 
rejected by any one, because he allowed the existence of 
bodies smaller than those we perceive, and attributed to 
them diverse sizes, figures, and motions, for no one can 
doubt that there are in reality such, as we have already 
shown; but it was rejected, in the first place, because he 
supposed that these corpuscles were indivisible, on which 
ground I also reject it; in the second place, because he 
imagined there was a vacuum about them, which I show 
to be impossible; thirdly, because he attributed gravity 
to these bodies, of which I deny the existence in any 
body, in so far as a body is considered by itself, because 
it is a quality that depends on the relations of situation 
and motion which several bodies bear to each other; and, 
finally, because he has not explained in particular how 
all things arose from the concourse of corpuscles alone, 
or, if he gave this explanation with regard to a few of 
them, his whole reasoning was far from being coherent 
[or such as would warrant us in extending the same 
explanation to the whole of nature]. This, at least, is 
the verdict we must give regarding his philosophy, if we 
may judge of his opinions from what has been handed 
down to us in writing. I leave it to others to determine 
whether the philosophy I profess possesses a valid coher- 
ency [and whether on its principles we can make the 
requisite number of deductions; and, inasmuch as the 
consideration of figure, magnitude, and motion has been 
admitted by Aristotle and by all the others, as well as by 
Democritus, and since I reject all that the latter has 
supposed, with this single exception, while I reject 
generally all that has been supposed by the others, it is 
plain that this mode of philosophising has no more affinity 
with that of Democritus than of any other particular sect]. 

XVI. How we may arrive at the knowledge of the 
figures [magnitudes], and motions of the insensible 
particles of bodies. 

The Earth 22c 

But, since I assign determinate figures, magnitudes, and 
motions to the msensible particles of bodies, as if I had 
seen them, whereas I admit that they do not fall under 
the senses, some one will perhaps demand how I have come 
by my knowledge of them. [To this I reply, that I first 
considered m general all the clear and distinct notions of 
material things that are to be found in our understanding, 
and that, finding no others except those of figures, magni- 
tudes, and motions, and of the rules according to which 
these three things can be diversified by each other, which 
rules are the principles of geometry and mechanics, I 
judged that all the knowledge man can have of nature 
must of necessity be drawn from this source; because all 
the other notions we have of sensible things, as confused 
and obscure, can be of no avail in affording us the know- 
ledge of anything out of ourselves, but must serve rather 
to impede it.] Thereupon, taking as my ground of 
inference the simplest and best known of the principles 
that have been implanted in our minds by nature, I con- 
sidered the chief differences that could possibly subsist 
between the magnitudes, and figures, and situations of 
bodies insensible on account of their smallness alone, and 
what sensible effects could be produced by their various 
modes of coming into contact; and afterwards, when I 
found like effects in the bodies that we perceive by our 
senses, I judged that they could have been thus produced, 
especially since no other mode of explaining them could 
be devised. And in this matter the example of several 
bodies made by art was of great service to me: for I recog- 
nise no difference between these and natural bodies beyond 
this, that the effects of machines depend for the most 
part on the agency of certain instruments, which, as they 
must bear some proportion to the hands of those who 
make them, are always so large that their figures and 
motions can be seen; in place of which, the effects of 
natural bodies almost always depend upon certain organs 
so minute as to escape our senses. And it is certain that 
all the rules of mechanics belong also to physics, of which 
it is a part or species [so that all that is artificial is withal 
natural] : for it is not less natural for a clock, made of the 
requisite number of wheels, to mark the hours, than for a 


226 The Principles of Philosophy 

tree, which has sprung from this or that seed, to produce 
the fruit pecuHar to it. Accordingly, just as those who 
are famihar with automata, when they are informed of 
the use of a machine, and see some of its parts, easily infer 
from these the way in which the others, that are not seen 
by them, arc made; so from considering the sensible 
effects and parts of natural bodies, I have essayed to 
determine the character of their causes and insensible 

XVII. That, touching the things which our senses do 
not perceive, it is sufficient to explain how they can be 
[and that this is all that Aristotle has essayed]. 

But here some one will perhaps reply, that although I 
have supposed causes which could produce all natural 
objects, we ought not on this account to conclude that they 
were produced by these causes; for^ just as the same 
artisan can make two clocks, which, though they both 
equally well indicate the time, and are not different in 
outward appearance, have nevertheless nothing resem- 
bling in the composition of their wheels ; so doubtless the 
Supreme Maker of things has an infinity of diverse means 
at his disposal, by each of which he could have made all 
the things of this world to appear as we see them, without 
it being possible for the human mind to know which of 
all these means he chose to employ. I most freely concede 
this ; and I believe that I have done all that was required 
if the causes I have assigned are such that their effects 
accurately correspond to all the phenomena of nature, 
without determining whether it is by these or by others 
that they are actually produced. And it will be sufficient 
for the use of life to know the causes thus imagined, for 
medicine, mechanics, and in general all the arts to which 
the knowledge of physics is of service, have for their end 
only those effects that are sensible, and that are accord- 
ingly to be reckoned among the phenomena of nature.^ 

^ " have for their end only to apply certain sensible bodies to 
each other in such a way that, in the course of natural causes, 
certain sensible effects may be produced; and we will be able to 
accomplish this quite as well by considering the series of certain 
causes thus imagined, although false, as if they were the true, 
since this scries is supposed similar as far as regards sensible 
effects." — French, 

The Earth 227 

And lest it should be supposed that Aristotle did or pro- 
fessed to do, anything more than this, it ought to be 
remembered that he himself expressly savs, at the com- 
mencement of the seventh chapter of the first book of the 
Meteorologies, that, with regard to things which are not 
manifest to the senses, he thinks to adduce sufficient 
reasons and demonstrations of them, if he only shows 
that they may be such as he explains them.^ 

XVIII. That nevertheless there is a moral certainty 
that all the things of this world are such as has been 
here shown they may be. 

But nevertheless, that I may not wrong the truth by 
supposing it less certain than it is, I will here distinguish 
two kinds of certitude. The first is called moral, that is, 
a certainty sufficient for the conduct of life, though, if we 
look to the absolute power of God, what is morally certain 
may be false. [Thus, those who never visited Rome do 
not doubt that it is a city of Italy, though it might be that 
all from whom they got their information were deceived.] 
Again, if any one, wishing to decipher a letter written in 
Latin characters that are not placed in regular order, 
bethinks himself of reading a B wherever an A is found, 
and a C wherever there is a B, and thus of substituting 
in place of each letter the one which follows it in the order 
of the alphabet, and if by this means he finds that there 
are certain Latin words composed of these, he will not 
doubt that the true meaning of the writing is contained 
in these words, although he may discover this only by 
conjecture, and although it is possible that the writer of 
it did not arrange the letters on this principle of alpha- 
betical order, but on som.e other, and thus concealed 
another meaning in it: for this is so improbable [especially 
when the cipher contains a number of words] as to seem 
incredible. But they who observe how many things 
regarding the magnet, fire, and the fabric of the whole 
world, are here deduced from a very small number of 
principles, though they deemed that I had taken them 

^ 'ETret 5^ irepi tQjv dcpavZv ry alcrdrjaei POfxl^OjULCv 'iKavws ciTrodeSerx^^' 
Kara rbv \6yov, iav els rb dvvarov dvaydyoJiJiev, tK rerCjv vvv (fyaivofi^- 
V03V VTToXd^OL TLS B.V (bde irepi tovtojv ^dXtara cvix^alveiv. ^lereuip. 
a. T. — Tr. 

22 8 The Principles of Philosophy 

oip at random and without grounds, will yet perhaps 
acknowledge that it could hardly happen that so many 
things should cohere if these principles were false. 

XIX. That we possess even more than a moral certainty 
of it. 

Besides, there are some, even among natural, things 
which we judge to be absolutely certain. [Absolute 
certainty arises when we judge that it is impossible a 
thing can be otherwise than as we think it.] This cer- 
tainty is founded on the metaphysical ground, that, as 
God is supremely good and the source of all truth, the 
faculty of distinguishing truth from error which he gave 
lis, cannot be fallacious so long as we use it aright, and 
distinctly perceive anything by it. Of this character are 
the demonstrations of mathematics, the knowledge that 
material things exist, and the clear reasonings that are 
formed regarding them. The results I have given in this 
treatise will perhaps be admitted to a place in the class of 
truths that are absolutely certain, if it be considered that 
they are deduced in a continuous series from the first and 
most elementary principles of human knowledge; espe- 
cially if it be sufficiently understood that we can perceive 
no external objects unless some local motion be caused by 
them in our nerves, and that such motion cannot be 
-caused by the fixed stars, owing to their great distance 
from us, unless a motion be also produced in them and in 
the whole heavens lying between them and us: for these 
points being admitted, all the others, at least the more 
general doctrines which I have advanced regarding the 
world or earth [e.g., the fluidity of the heavens], will 
appear to be almost the only possible explanations of the 
phenomena they present. 

XX. That, however, I submit all my opinions to the 
authority of the church. 

Nevertheless, lest I should presume too far, I affirm 
nothing, but submit all these my opinions to the authority 
of the church and the judgment of the more sage; and I 
desire no one to believe anything I may have said, unless 
he is constrained to admit it by the force and evidence of 


{From the Reply to the Second Objections — Latin, 1670, 
pp. 85-91. French, Gamier, Tom. 11. , pp. 74-84) 

Reasons which establish the Existence of God, 
AND THE Distinction between the Mind ani> 
Body of Man, disposed in Geometrical Order 


I. By the term thought {cogitatio, pensee), I comprehend 
all that is in us, so that we are immediately conscious of it. 
Thus, all the operations of the will, intellect, imagination^ 
and senses, are thoughts. But I have used the word 
immediately expressly to exclude whatever follows or 
depends upon our thoughts: for example, voluntary 
motion has, in truth, thought for its source (principle)^ 
but yet it is not itself thought. [Thus walking is not 
a thought, but the perception or knowledge we have of 
our walking is.] 

II. By the word idea I understand that form of any 
thought, by the immediate perception of which I am 
conscious of that same thought; so that I can express 
nothing in words, when I understand what I say, without 
making it certain, by this alone, that I possess the idea 
of the thing that is signified by these words. And thus 
I give the appellation idea not to the images alone that 
are depicted in the phantasy; on the contrary, I do not 
here apply this name to them, in so far as they are in the 
corporeal phantasy, that is to say, in so far as they are 
depicted in certain parts of the brain, but only in so far 
as they inform the mind itself, when turned towards that 
part of the brain. 

III. By the objective reality of an idea I understand the 
entity or being of the thing represented by the idea, in so 
far as this entity is in the idea; and, in the same manner, 


230 Appendix 

it may be called either an objective perfection or objective 
artifice, etc. {artijictujn ohjectivum). For all that we 
conceive to be in the objects of the ideas is objectively 
[or by representation] in the ideas themselves. 

IV. The same things are said to be formally in the 
objects of the ideas when they are in them such as we 
conceive them; and they are said to be in the objects 
eminently when they are not indeed such as we conceive 
them, but are so great that they can supply this defect by 
their excellence. 

V. Everything in which there immediately resides, as 
in a subject, or by which there exists any object we per- 
ceive, that is, any property, or quality, or attribute of 
which we have in us a real idea, is called substance. For 
we have no other idea of substance, accurately taken, 
except that it is a thing in which exists formally or emi- 
nently this property or quality which we perceive, or 
which is objectively in some one of our ideas, since we 
are taught by the natural light that nothing can have no 
real attribute. 

VI. The substance in which thought immediately 
resides is here called mind {mens, esprit). I here speak, 
however, of meiis rather than of anima, for the latter is 
equivocal, being frequently applied to denote a corporeal 

VII. The substance which is the immediate subject of 
local extension, and of the accidents that presuppose this 
extension, as figure, situation, local motion, etc., is called 
body. But whether the substance which is called mind 
be the same with that which is called body, or whether 
they are two diverse substances, is a question to be here- 
after considered. 

VIII. The substance which we understand to be 
supremely perfect, and in which we conceive nothing that 
involves any defect, or limitation of perfection, is calledG^?^. 

IX. When we say that some attribute is contained in 
the nature or concept of a thing, this is the same as if we 
said that the attribute is true of the thing, or that it may 
be affirmed of the thing itself. 

X. Two substances are said to be really distinct, when 
each of them may exist without the other. 


Appendix 231 


ist. I request that my readers consider how feeble are 
the reasons that have hitherto led them to repose faith 
in their senses, and how uncertain are all the judgments 
which they afterwards founded on them; and that they 
will revolve this consideration in their mind so long and 
so frequently, that, in fine, they may acquire the Tiabit 
of no longer trusting so confidently in their senses; for I 
hold that this is necessary to render one capable of appre- 
hending metaphysical truths. 

2nd. That they consider their own mind, and all those 
of its attributes of which they shall find they cannot 
doubt, though they may have supposed that all they ever 
received by the senses was entirely false, and that they 
do not leave off considering it until they have acquired 
the habit of conceiving it distinctly, and of believing that 
it is more easy to know than any corporeal object. 

3rd. That they diligently examine suc^h propositions 
as are self-evident, which they will find within themselves, 
as the following: — That the same thing cannot at once 
be and not be ; that nothing cannot be the efficient cause 
of anything, and the like; — and thus exercise that clear- 
ness of understanding that has been given them by nature, 
but which the perceptions of the senses are wont greatly 
to disturb and obscure — exercise it, I say, pure and 
delivered from the objects of sense; for in this way the 
truth of the following axioms will appear very evident to 

4th. That they examine the ideas of those natures 
which contain in them an assemblage of several attributes, 
such as the nature of the triangle, that of the square, or 
of some other figure; as also the nature of mind, the 
nature of body, and above all that of God, or of a being 
supremely perfect. And I request them to observe that 
it may with truth be affirmed that all these things are in 
objects, which we clearly conceive to be contained in them: 
for example, because that, in the nature of the rectilmeal 
triangle, this property is found contained— viz., that its 
three angles are equal to two right angles, and that in the 
nature of body or of an extended thing, divisibihty is 

232 Appendix 

comprised (for we do not conceive any extended thing so 
small that we cannot divide it, at least in thought) — it is 
true that the three angles of a rectilineal triangle are equal 
to two right angles, and that all body is divisible. 

5th. That they dwell much and long on the contempla- 
tion of the supremely perfect Being, and, among other 
things, consider that in the ideas of all other natures, 
possible existence is indeed contained, but that in the 
idea of God is contained not only possible but absolutely 
necessary existence. For, from this alone, and without 
any reasoning, they will discover that God exists: and 
it will be no less evident in itself than that two is an equal 
and three an unequal number, with other truths of this 
sort. For there are certain truths that are thus manifest 
to some without proof, which are not comprehended by 
others without a process of reasoning. 

6th. That carefully considering all the examples of 
clear and distinct perception, and all of obscure and con- 
fused, of which I spoke in my Meditations, they accustom 
themselves to distinguish things that are clearly known 
from those that are obscure, for this is better learnt by 
example than by rules; and I think that I have there 
opened up, or at least in some degree touched upon, all 
examples of this kind. 

7th. That readers adverting to the circumstance that 
they never discovered any falsity in things which they 
clearly conceived, and that, on the contrary, they never 
found, unless by chance, any truth in things which they 
conceived but obscurely, consider it to be wholly irrational, 
if, on account only of certain prejudices of the senses, or 
hypotheses which contain what is unknown, they call in 
doubt what is clearly and distinctly conceived by the 
pure understanding; for they will thus readily admit the 
following axioms to be true and indubitable, though I 
confess that several of them might have been much better 
unfolded, and ought rather to have been proposed as 
theorems than as axioms, if I had desired to be more exact. 


I. Nothing exists of which it cannot be inquired what 
is the cause of its existing; for this can even be asked 


Appendix 233 

respecting God; not that there is need of any cause in 
order to his existence, but because the very immensity 
of his nature is the cause or reason why there is no need 
of any cause of his existence. 

II. The present time is not dependent on that which 
immediately preceded it; tor this reason, there is not 
need of a less cause for conserving a thing than for at 
first producing it. 

III. Any thing or any perfection of a thing actually 
existent cannot have nothing, or a thing non-existent, 
for the cause of its existence. 

IV. All the reaUty of perfection which is in a thing is 
found formally or eminently in its first and total cause. 

V. Whence it follows likewise, that the objective reality 
of our ideas requires a cause in which this same reality 
is contained, not simply objectively, but formally or 
eminently. And it is to be observed that this axiom 
must of necessity be admitted, as upon it alone depends 
the knowledge of all things, whether sensible or insensible. 
For whence do we know, for example, that the sky exists ? 
Is it because we see it? But this vision does not affect 
the mind unless in so far as it is an idea, and an idea 
inhering in the mind itself, and not an image depicted on 
the phantasy; and, by reason of this idea, we cannot 
judge that the sky exists unless we suppose that every 
idea must have a cause of its objective reality which is 
really existent; and this cause we judge to be the sky 
itself, and so in the other instances. 

VI. There are diverse degrees of reality, that is, of 
entity [or perfection]: for substance has more reality 
than accident or mode, and infinite substance than finite; 
it is for this reason also that there is more objective reality 
in the idea of substance than in that of accident, and in 
the idea of infinite than in the idea of finite substance. 

VII. The will of a thinking being is carried voluntarily 
and freely, for that is of the essence of will, but never- 
theless infallibly, to the good that is clearly known to it; 
and, therefore, if it discover any perfections which it does 
not possess, it will instantly confer them on itself if they 
are in its power [for it will perceive that to possess them 
is a greater good than to want them.] 

2 34 Appendix 

VIII. That which can accomplish the greater or more 
difficult, can also accomplish the less or the more easy. 

IX. It is a greater and more difficult thing to create or 
conserve a substance than to create or conserve its attri- 
butes or properties; but this creation of a thing is not 
greater or more difficult than its conservation, as has 
been already said. 

X. In the idea or concept of a thing existence is con- 
tained, because we are unable to conceive anything unless 
under the form of a thing which exists; but with this 
difference that, in the concept of a limited thing, possible 
or contingent existence is alone contained, and in the 
concept of a being sovereignly perfect, perfect and 
necessary existence is comprised. 


The existence of God is known from the consideration 
of his nature alone. 


To say that an attribute is contained in the nature or 
in the concept of a thing is the same as to say that this 
attribute is true of this thing, and that it may be affirmed 
to be in it. (Definition IX.) 

But necessary existence is contained in the nature or 
in the concept of God (by Axiom X.). 

Hence it may with truth be said that necessary existence 
is in God, or that God exists. 

And this syllogism is the same as that of which I made 
use in my reply to the sixth article of these objections; 
and its conclusion may be known without proof by those 
who are free from all prejudice, as has been said in Postu- 
late V. But because it is not so easy to reach so great 
perspicacity of mind, we shall essay to establish the same 
thing by other modes. 


The existence of God is demonstrated, a posteriori^ from 
this alone, that his idea is in us. 


Appendix 2?c 


The objective reality of each of our ideas requires a 
cause in which this same reahty is contained, not simply 
objectively, but formally or eminently (by Axiom V.) 

But we have in us the idea of God (by Definitions II. 
and VIII.), and of this idea the objective reality is not 
contained in us, either formally or eminently (by Axiom 
VI.), nor can it be contained in any other except in God 
himself (by Definition VIII.). 

Therefore this idea of God which is in us demands God 
for its cause, and consequently God exists (by Axiom III.). 


The existence of God is also demonstrated from this, 
that we ourselves, who possess the idea of him, exist. 


If I possessed the power of conserving myself, I should 
likewise have the power of conferring, ajortiori, on myself, 
all the perfections that are awanting to me (by Axioms 
VIII. and IX.), for these perfections are only attributes 
of substance, whereas I myself am a substance. 

But I have not the power of conferring on myself these 
perfections, for otherwise I should already possess them 
(by Axiom VIL). 

Hence, I have not the power of self-conservation. 

Further, I cannot exist without being conserved, so long 
as I exist, either by myself, supposing I possess the power, 
or by another who has this power (by Axioms I. and II.). 

But I exist, and yet I have not the power of self- 
conservation, as I have recently proved. Hence I am 
conserved by another. 

Further, that by which I am conserved has in itself 
formally or eminently all that is in me (by Axiom IV.). 

But I have in me the perception of many perfections 
that are awanting to me, and that also of the idea of God 
(by Definitions II. and VIII.). Hence the perception of 
these same perfections is in him by whom I am conserved. 

Finally, that same being by whom I am conserved 

236 Appendix 

cannot have the perception of any perfections that are 
awanting to him, that is to say, which he has not in him- 
self formally or eminently (by Axiom VII.); for having 
the power of conserving me, as has been recently said, 
he should have, ajorttori, the power of conferring these 
perfections on himself, if they were awanting to him (by 
Axioms VIII. and IX.). 

But he has the perception of all the perfections which 
I discover to be wanting to me, and which I conceive can 
be in God alone, as I recently proved: 

Hence he has all these in himself, formally or eminently, 
and thus he is God. 


God has created the sky and the earth and all that is 
therein contained; and besides this he can make all the 
things which we clearly conceive in the manner in which 
we conceive them. 


All these things clearly follow from the preceding 
proposition. For in it we have proved the existence of 
God, from its being necessary that some one should exist 
in whom are contained formally or eminently all the per- 
fections of which there is in us any idea. 

But we have in us the idea of a power so great, that by 
the being alone in whom it resides, the sky and the earth, 
etc., must have been created, and also that by the same 
being all the other things which we conceive as possible 
can be produced. 

Hence, in proving the existence of God, we have also 
proved with it all these things. 


The mind and body are really distinct. 


All that we clearly conceive can be made by God in the 
manner in which we conceive it (by foregoing Corollary). 

Appendix 237 

But we clearly conceive mind, that is, a substance 
which thinks, without body, that is to say, without an 
extended substance (by Postulate II.); and, on the other 
hand, we as clearly conceive body without mind (as every 
one admits): 

Hence, at least, by the omnipotence of God, the mind 
can exist without the body, and the body without the 

Now, substances which can exist independently of each 
other, are really distinct (by Definition X.). 

But the mind and the body are substances (by Defi- 
nitions v., VI., and VII.), which can exist independently 
of each other, as I have recently proved: 

Hence the mind and the body are really distinct. 

And it must be observed that I have here made use of 
the omnipotence of God in order to found my proof on it, 
not that there is need of any extraordinary power in order 
to separate the mind from the body but for this reason, 
that, as I have treated of God only in the foregoing 
propositions, I could not draw my proof from any other 
source than from him: and it matters very little by what 
power two things are separated in order to discover that 
they are really distinct. 




The term perception [perceptio] has a much wider signification in 
the writings of Descartes and the Cartesians than in the hterature 
of the schools of philosophy in our times. Perception is, at present, 
used to denote the immediate knowledge we obtain through sense' 
or even still further restricted to the apprehension of what have 
been called the primary qualities of matter; with the Cartesians, 
and the older philosophers generally, the word is employed in the 
same sense in which we use conscioxisness , to denote an act of mind 
by which we merely apprehend or take note of the object of thought 
or consciousness, considered as distinguished from any affirmation 
or negation (judgment) regarding it. Accordingly, in Cartesian 
literature perception is synonymous with cognition, when, in the 
narrower sense of the term, it is said to consist in the apprehension 
ef a thing, or in the immediate consciousness of that which is known, 
as opposed to judgment and reasoning. It thus includes both 
the representative knowledge of imagination (and with the Car- 
tesians, of sense), and the mediate or representative knowledge 
given in a notion or concept ; for we cannot, either in imagination 
or conception, represent without being conscious of the representa- 
tion, i.e., without perceiving or immediately apprehending it. 
Percipere in Cartesian literature is thus, with greater or less pro- 
priety, considered as equivalent to cognoscere, intelligere (in the 
narrower sense of these terms), rem menti propositam concipere, 
intueri ; cogitatione sibi representare ; rerum ideas intueri ; res per 
ideas videre ; rem per intellectus ideam intueri, cernere ; rei ideam 
in intellectu habere. Perceptio is properly synonymous with per- 
ceptio simplex, apprehensio seu apprehensio simplex [q. prehensio 
objecti ab intellectu) intellectio simplex, visio simplex, cognitio, and 
less properly with conceptus, notio, idea rei. In logical language, 
the character of perception is expressed by saying that the act has 
for its object a thema simplex, i.e., in the language of Descartes, 
either substance or attribute, as opposed to the thema conjunctum 
seu compositum, or notionum complexio per affirmationem et nega- 
iionem. i.e., enunciatio, or, in the language of Descartes, a truth. — 
Prin. of Phil., P. I., §48. Claubergius, Op. P. I., pp. 334, 503. 
(Ed. 1691.) Flenderus, Log. Cont. Claub. lU. §§ i, 5. (4th Ed.) 

To illustrate more particularly the nature and sphere of percep- 
tion, as the term is used in the Cartesian school, it is necessary to 
attend to the division of the phaenomena of consciousness, adopted 
by Descartes, and current among his followers. Descartes divides 
all our thoughts {cogitationes) — and with him thought is the general 
name for each mode or phasnomenon of consciousness — into two 
grand classes, viz., the Activities and Passivities of mind {acttones 
et passiones sive affectus animce), the distinguishing element of these 
two classes being, that in the former case the mind of itself deter- 


240 Notes 

mines its own modification; in the latter it is determined to it, 
by some action, to wit, foreign from the will. The first class 
■embraces all the acts of the will, or the volitions {volitiones sivc 
operationes voluntatis) y inasmuch as all such modifications of mind 
are considered by him as determinable, and actually determined,, 
by the power of free choice or will, i.e.^ by the mind itself; and 
under volition {i.e., to use the language of his followers, latio 
quaedam animi tendens ad objectum in idea propositum) he compre- 
hends judgment and will proper [velle et nolle), according as the 
object is regarded under the notions of the true and the false, or 
of the good and the had. To the second class he refers all the 
cognitive acts of the mind, considered merely as apprehensive of 
their objects [perceptiones sive operationes intellectus) , inasmuch 
as our apprehensions are not made arbitrarily, or at the pleasure 
of our will, but determined by their objects, and are thus, in a sense, 
passions or passivities. In this way all the acts, whether of sense, 
memory, imagination, or the pure intellect, are but different modes 
of perceiving; for in each we only know as we are conscious of, 
or apprehend, the object of the act. Further, as each mental 
modification has a reality for us only in so far as we actually appre- 
hend or are conscious of it, it is plain that, in every actual mode 
of mind, there is involved a consciousness, or, in the Cartesian 
language, a perception ; and thus we are said to perceive not only 
when in sense we apprehend by idea or representation extension 
or figure — the qualities of somewhat lying beyond ourselves, or the 
representative object in imagination, but likewise when we are 
conscious of the forth-putting of an act of will or of being affected 
by joy or hope. More particularly as, according to the Cartesian 
doctrine, the consciousness of a modification of mind, a volition, 
for example, is, though in thought [ratione) separable, not really 
distinct from this modification itself, all modes of mind whatsoever, 
as participating of consciousness, are, in a sense, perceptions ; for 
this implies nothing more than that they exist in consciousness. 
In this sense perception is not contrasted with, but comprehends 
volition, though extending further. As some modifications of 
mind, however, though only manifesting themselves through 
knowledge, are yet not apprehension simply or even knowledge, 
but to use his own phrase, have other forms, as volition, we may 
consider them in reference to these other characters; and as, on 
the Cartesian doctrine, these characters are negative of each other, 
we thus obtain classes not only in opposition, but in fundamental 
contrast. These distinguishing characteristics are, as we have 
seen, the qualities of activity and of passivity, which thus afford 
two grand divisions of the mental modifications, called respectively 
volitions and perceptions. 

That perception was only logically discrimnated fromi its object 
on the doctrine of Descartes, will be manifest from what follows: — 

** I observe (he says) that whatever is done, or recently happens, 
is generally called by the philosophers passion, in respect of the 
subject to which it happens, and action in respect of that which 
causes it to take place, so that, although agent and patient are 
often very diverse, action and passion nevertheless remain one and 
the same thing, having these two names by reason of the two different 
subjects to which it can be referred'' — De Pass., P. i., art. i. 

'* Our perceptions are of two species: some have the mind for 
their cause, and others the body. Those that have the mind for 
their cause are the perceptions of our volitions, and of all our 

Notes 241 

imaginations that depend on it; for it is certain that we camwt will 
anythtng without perceiving by the same means that we will it a^d 
although in respect of our mind it may be an action to will a thing 
we may say that it is also m it a passion to perceive that it w Hs- 
nevertheless, because this perception and volition are only in reality 
the same thing, the denomination is always made from the more 
noble, and thus we are not accustomed to caU it a passion but 
simply an action. '--Ibid Art 19. Con. on the note in general. 
Art. 17. Prm. of Phil., P. I., §32. Med. Ill pp 07 qS Ed 
P. II., CXV., quoted below. Hamilton's Reid.' Note D d*d 8^6' 
^yy. Compare note ii. Idea. ' ' 

Under the head of perception it may be necessary to remark 
farther that the term perception [perceptio) is not used in reference 
to sense without the adjunct sensus or sensuum~ihe terms in this 
relation being sensus, sensatio, idea, and the verb sentire not 

II. IDEA — p. 72 

The meaning attached to the term idea in the writings of 
Descartes is by no means uniform or constant. The first grand 
distinction in the signification of the word arises from its applica- 
tion by Descartes to denote indifferently a material or a mental 
modification; and this in relation to sense and imagination. Con- 
sidered with respect to these faculties, idea is sometimes applied 
to designate the impression on the brain or material organism 
generally, to which the idea proper or mental modification is 
attached, and at other times to mark the mental modification 
itself, regarded as the object of the faculty. As instances of the 
former application of the word, we may adduce the following 
passages: — *' Ideam quam formant hi spiritus." — Tract, de Homine, 
§ 84. ** Glandula ideas objectorum, quae in aliorum sensuum 
organa agunt, aeque facile recipere possit." — Ibid. § 85. " Ideas 
quas sensus externi in phantasiam mittunt." — Diopt. cap. iv. § 6. 
To obviate the ambiguity incidental to this twofold and quite 
opposite use of the term, De la Forge, an eminent Cartesian, 
denominated the movement in the organism species, or corporeal 
species, reserving idea for the modification of the mind alone. — 
Traite de I'Esprit de I'Homme, chap. x. p. 99. Hamilton's Reid, 
p. 834. 

Descartes himself, indeed, in the course of the controversies to 
which his speculations gave rise, became aware of the necessity of 
distinguishing in expression the material from the mental idea; 
and in order to this he seems occasionally disposed to refuse the 
appellation idea to the material modification, while he more fre- 
quently uses the term image [imago], than idea in this relation. 
One of these passages I shall quote, not only in proof of this, but 
also as establishing the fact of the reality and distinctness of the 
material and mental modifications. '* I do not simply (he says) 
call by the name idea the images that are depicted in the phantasy; 
on the contrary, I do not call them by this name in so far as they 
are in the corporeal phantasy; but I designate generally by the 
term idea all that is in our mind when we conceive a thing in whatever 
manner we may conceive it." — Lett. Ixxv., Gamier, tom. iv. p. 319. 

It should be observed, however, that by idea in the sense of cor- 
poreal species, Descartes did not mean a picture, likeness, or image 
of the object existing in the brain, but simply a certain organic 


242 Notes 

movement, or agitation of the nerves, determined by the object 
and communicated to the brain, the seat of the sensus communis. 
This purely material modification had, on the one hand, not neces- 
saurily any resemblance to the object which was the cause of it, and 
therefore was not representative of it ; nor, on the other, should it 
be supposed that it in any way resembled, far less was identical 
with, the (mental) idea connected with it, since notwithstanding 
certain loose statements, there is sufficient ground to hold that, 
on the doctrine of Descartes, the corporeal impression was no 
object of perception or consciousness at all. As these are points 
of essential importance towards a right comprehension of the 
philosophy of Descartes, I may be allowed to enter somewhat into 
detail ; and first of all, I shall refer to the passages in which he has 
distinctly laid down the doctrines here attributed to him. 

** That the ideas which the external senses send into the phantasy 
are not images of the objects; or at least that there is no need of 
their being like them. 

" It must be observed, besides, that the mind does not stand 
in need of images sent from objects to the brain in order to perceive 
(as is the generally received opinion of the philosophers); or at 
least that the nature of these images is to be conceived far other- 
wise than is commonly done. For, as philosophers consider in 
them nothing beyond their resemblance to the objects they repre- 
sent, they are unable to show how these images can be formed by 
the objects, and received into the organs of the external senses, 
and finally transmitted by the nerves to the brain. And they had 
no ground to suppose there were such images, beyond observing 
that our thought can be efficaciously excited by a picture to con- 
ceive the object pictured; from which it appeared to them that the 
mind must be, in the same way, excited to apprehend the objects 
which affect the senses, by means of certain small images delineated 
in our head. Whereas we ought to consider that there are many 
things besides images that can excite our thougkts; as, for example, 
words and signs which in no way resemble the things they signify. 
And if, that we may depart as little as possible from the commonly 
received opinions, we may be allowed to concede that the objects 
we perceive are really depicted in the brain, we must at least remark 
that no image is ever absolutely hke to the object it represents; 
for in that case there would be no distinction between the object 
and its image; but that a partial likeness {rudem similitudinem) 
is sufficient, and that frequently even the perfection of images 
consists in their not resembling the objects as far as they might. 
Thus, we see that engravings formed merely by the placing of ink 
here and there on paper, represent to us forests, cities, men, and 
even battles and tempests; and yet of the innumerable qualities 
of these objects which they exhibit to our thought, there is none 
except the figure of which they really bear the likeness. And it is 
to be remarked that even this likeness is very imperfect, since on 
a plane surface they represent to us bodies variously rising and 
sinking; and even that according to the rules of perspective, they 
frequently represent circles better by ovals than by other circles, 
and squares by rhombi than by other squares, and so on in other 
instances; so that in order to the absolute perfection of the image, 
and the accurate delineation of the object, the former more fre- 
quently requires to be unlike the latter." — Diopt. cap. iv. § 6, C. § 7. 
Prin. of Phil., P. iv. §§ 197, 198. 

" Whoever has well comprised (says Descartes in contravention 

Notes 247 

of the doctrine of Regius, that all our common notions owe their 
origin to observation and tradition), the extent and Hmits of our 
senses and what precisely by their means can reach our faculty 
of thinking, must admit that no idea or objects are represented to 
us by them such as we form them by thought ; so that there is nothing 
in our ideas that is not natural to the mind or to the faculty of 
thinking which it possesses, if we but except certain circumstances 
that pertain only to experience; for example, it is experience alone 
that leads us to judge that such and such ideas, which are now 
present to the mind, are related to certain objects that are out of 
us; not in truth that those things transmitted them into our mind by 
the organs of the senses such as we perceive them ; but because they 
transmitted something which gave occasion to our mind, by the natural 
faculty it possesses, to form them at that time rather than at another. 
For, as our author himself avers in article 19, in accordance with 
the doctrine of my Principles, nothing can come from extenial 
objects to our mind by the medium of the senses, except certain 
corporeal movements ; but neither these movements themselves nor 
the figures arising from them, are conceived by us such as they are in 
the organs of sense, as I have amply explained in the Dioptrics: 
whence it follows that even the ideas of motion and figures are 
naturally in us. And much more the ideas of pain, colours, sounds, 
and of other similar things, must be natural to us, to the end thai 
our mind, on occasion of certain corporeal movements, with which 
they have no resemblance, may be able to represent them to itself'' — 
Remcirks on the Programme of Regius, Ep. P. i. xcix. (Ed. 1668), 
or torn. iv. Lett, xxxviii. of Garnier's Ed. 

" Finally, I hold that all those (ideas) which involve no negation 
or affirmation, are innate in us, for tlie organs of the senses convey 
nothing to us of the same character as the idea which is formed on 
occasion of them, and thus the idea must have been previously 
in us," — Ep. P. ii. Iv., or Gamier's Ed. tom. iv. Lett. Ixix. 

" Whence do we know that the sky exists? Is it because we 
see it? But this vision does not affect the mind unless in so far 
as it is an idea, and an idea inhering in the mind itself, and not an 
image depicted on the phantasy.'' — App. Ax. 5, p. 233. 

** / hold that there is no other difference between the mind and its 
ideas than between a piece of wax and the diverse figures of which it 
is capable. And since the receiving diverse figures is not properly 
an action in the wax, but a passion; so it seems to me to be also 
a passion in the mind that it receives this or that idea; and I 
consider that except its volitions it has no actions, but that its 
ideas are induced upon it, partly by objects affecting the senses, 
partly by the impressions that are in the brain, and partly also by 
the dispositions which have gone before in the mind itself, and by 
the movements of its will." — Ep. P. i. cxv. 

** The mind always receives these (its perceptions) from the thmgs 
represented by them." — De Pass., part i., art. 17. 

Among Cartesians, compare De la Forge, De 1' Esprit de T Homme, 
cap. x. Geulinx, Dictata in Prin. Phil. P. iv. § 189. Malebranche, 
Recherche de la Verite, Liv. ii. ; De 1' Imagination, chap. v. § i ; also 
Liv. i. Des Sens, chap. x. § 5. 

I am aware that some maintain that Descartts held the material 
impression to be an object of consciousness, an opinion to which 
both Reid and Stewart incline (see Reid's Essays on the Intellectual 
Powers; essay ii., chap, viii.; Stewart's Dissertation, Note N. 
p. 245; Elements, part i., chap, i., note, p. 45, ed. 1850). That 

244 Notes 

such is not the doctrine of Descartes, is manifest from the passages 
ahready cited. It may be necessary, however, in order to a fuller 
•consideration of the question, to refer to those doubtful statements 
which at first sight appear to give some countenance to the sup- 

I shall, first of all, quote and give references to what seem the i 
strongest of the ambiguous passages. '* I easily understand," he 
says, " that if some body exists with which my mind is so united 
as to be able, as it were, to consider it when it chooses, it may thus 
imagine corporeal objects, so that this mode of thinking differs 
from pure intellection only in this respect, that the mind in con- 
ceiving, turns in some way upon itself, and considers some one of 
the ideas it possesses within itself; but, in imagining, it turns 
toward the body, and contemplates in it some object conformed 
to the idea which it either conceived of itself or apprehended by 
■sense." — Med. vi., p. 128. 

" The former, or corporeal species which must be in the brain in 
order to imagination, are not thoughts; but the operation of the 
mind imagining or turning towards these species, is a thought." — 
Ep. p. ii. liv. (De Pass. p. i., art. 35. Appendix, Dcf. ii., p. 229). 

These and similar passages might seem, at first sight, to counte- 
nance the supposition that Descartes admitted a knowledge of the 
corporeal species or organic impression. Such an interpretation 
is, however, rash and untenable, were there no other ground for 
rejecting it, save the various contradictions of the principles of the 
philosophy of which it is supposed to form a part, for these are so 
many and so manifest, that we could hardly suppose such a thinker 
as Descartes to have allowed them to escape his notice. Before 
showing that the passages in themselves do not really warrant 
the interpretation here referred to, I shall point out its general 
inconsistency, not only with the main principle, but with certain 
particular doctrines of Cartesianism, and these the most important 
and distinctive. 

In the first place, then, had Descartes admitted a knowledge of 
the material impression, either in sense or imagination, and, be it 
observed, an immediate knowledge is the only supposable, he must 
have allowed an immediate consciousness of matter, for the cor- 
poreal species is a material object. But this would have been to 
contradict the fundamental principle of his philosophy, according 
to which, mind, on account of its absolute diversity from body, is 
supposed to be able to hold no immediate converse with matter, 
but only to be cognisant of it by means of its own modifications, 
determined hyperphysically on occasion of certain affections of the 
body with which it is conjoined. And thus, if the mind be immedi- 
ately cognisant of the corporeal species, what occupies the prominent 
and distinctive place in Cartesianism, — viz., the host of mental 
ideas representative of the outward object, becomes forthwith the 
superfluity and excrescence of the system ; for if the mind can take 
immediate cognisance of the corporeal species, i.e. of matter, why 
postulate a mental representation in order to the perception of the 
outward object ? 

But, in the second place, whether the material impression be an 
object of consciousness or not, Descartes must still be held to allow 
the existence of a mental modification or idea. The species, there- 
fore, on the hypothesis that it is an object of consciousness is either 
really identical with the mental idea, or it is different from it. To 
take the former supposition, or that of the identity of the material 

Notes 245 

and mental modifications, it will follow that mind and matter are 
no longer distinguishable, are no longer diverse substances seeing 
their modifications coincide— a tenet no less at variance with the 
entire course of the speculations of Descartes, than is the doctrine 
from which it flows with the numerous explicit statements in 
which he decides the total diversity of the material and mental 
ideas, as modifications of substances in themselves distinct But 
the organic impression, if not identical with, must be diverse from 
the mental idea. Now as, on the hypothesis in question the 
material idea is perceived, and as the mental is likewise an object 
of perception, there must be in each of the faculties of sense and 
imagination a two-fold object. For such a doctrine, there is not 
the shadow of a ground in all the writings of Descartes. 

But, in the third place, let it be supposed that Descartes did not 
allow the existence of mental ideas at all, and therefore only a 
single object in perception, and that the organic impression, even 
with this gratuitous allowance a palpable contradiction in the 
doctrine of the philosopher would arise. The organic impression, 
in order to constitute the representative idea of the object, must 
represent the object, not suggest it or represent it maierially 
{materialiter) , as a natural sign, for the object could not be simply 
suggested to the mind or thus represented, without appearing in 
a mental modification or idea, which is contrary to the hypothesis. 
But an object that is material, and at the same time representative, 
must, if it represent by itself, represent intentionally [intcntionaliter) ; 
in other w^ords, it must resemble the object it represents, or be the 
image or likeness of it. It is the property of mind alone to be 
capable of representing something different from itself, or even 
quite opposed, in a modification not at all resembling the thing 
represented; as, for example, an extended object in an unextended 
modification. But the resemblance of the material idea to the 
outward object, is a doctrine explicitly denied by Descartes. — 
{Vide Remarks on Programme of Regius, quoted above, Prin. of 
Phil.. P. iv., §§ 197, 198.) 

But, finally, the whole hypothesis makes Descartes contradict not 
only his own doctrine of representation, but destroy the general 
conditions of any representative doctrine whatever: for, as the 
only ground on which a doctrine of representation can be supposed 
necessary, is that the mind is not immediately percipient of the 
outward object, if Descartes at the same time holds that the repre- 
sentation, itself material and an object external to the mind, be- 
cause existing in the brain, is perceived, he must allow to the mind, 
at first hand, that power on the denial of the existence of which the 
assertion of the need of a representative object is founded. 

These considerations are, I think, sufficient to show, that it is at 
least highly improbable, that Descartes meant in the passages 
quoted to allow to the mind a consciousness of the organic impres- 
sion in sense and imagination. To have done so, would have been 
to fill his philosophy with anomalies and contradictions of the 
most palpable kind. 

But let us attend shortly to the passages themselves, to discover 
whether they render such an interpretation of them imperative. 
In the passages quoted, the mind is said to turn itself towards the 
species, and these again are said to inform [informare) the mind. 

With regard to the first phrase, conversion towards the species, it 
will be found, by a reference to the passages in which it occurs, that 
it is always used as descriptive of the acts of sense and imagination^ 



when these are spoken of in contrast to the act of the pure intellect, 
or that faculty whose exercise is independent of all organic impres- 
sion; and then the contrast indicated is in the origin or source of 
the ideas, or objects of these faculties, those of sense and imagination 
having their (remote) source in body, — those of intellect, their 
(immediate) origin in the mind itself. In this way, all that con- 
version towards the species indicates, is merely that the mind 
does not receive certain ideas directly from itself, but is in some 
way dependent for at least their actual presence on certain con- 
ditions of the bodily organism. And this, it is manifest, does not 
necessarily imply the consciousness by the mind of the organic 

Again, the corporeal species may in its turn be said to inform the 
mind [informare rnentem), inasmuch as it is to it the mental modifi- 
cation or idea, viewed apart from its hyperphysical origin, is 
immediately attached, and on occasion of which it is revealed to 
consciousness ; and this on the law of the union of mind and body, 
as parts of the same whole. In the same sense, Deity is said to 
inform the mind, in so constituting it as that in the course of the 
development of its powers, the knowledge of himself should naturally 

But, in the second place, the species may, in a literal sense, be 
said to inform the mind, for the word, in iis strict acceptation, 
merely denotes the giving a particular form or shape to a thing; 
and in the Cartesian phraseology, the spiritual notions or mental 
ideas were but the different forms of the mind in which its acts were 
clothed, limited, and determined. — Vide Appendix, Def. ii., p. 229. 
De la Forge, De I'Esprit, chap, x., p. 131 and passim. Claub. 
Op. p. ii., p. 606. 

The doctrine of Descartes on this point seems to be well put by 
Chauvin, when, after noticing the doctrines of certain of the Peripa- 
tetics regarding species, he says: — "There are, however, among 
more recent philosophers, not a few who retain the nomenclature 
of species impressa and expressa. But with them the species 
impressa is nothing more than a certain motion impressed either 
mediately or immediately, by external objects, on the parts of the 
body, and thence by the nerves transmitted to the brain, or a certain 
commotion of the fibres of the brain, proceeding from the agitation 
of the animal spirits flowing in the brain; which, as they have no 
resemblance to the objects of nature, are esteemed representamens 
of these things, on no other account than because the mind on occasion 
of them [i.e., the motions], makes the things present to itself, and 
contem.plates the same in its own ideas therefrom arising. . . . 

But the species expressa is nothing more than that notion of the 
mind which is expressed on the presence of the species impressa, 
and by attention to and inspection (intuitione) of which the thing 
itself is known." — Lexicon Rationale, Species (1692). Con. Prin. 
of Phil., part iv. §§ 189, 197, 198. 

But, lastly, the whole ambiguity is probably due to the extreme 
timidity of the philosopher, and his anxious solicitude to bring the 
results of his own independent reflection into an apparent harmony 
with the opinions generally received in his time; which led him 
frequently to clothe his really new doctrines in the current forms 
of expression. 

There is thus not even on the special ground of the ambiguous 
passages themselves, any reason to suppose that Descartes ever 
departed from a doctrine essential to the consistency of his philo- 



sophy, viz., the non- consciousness of the organic impression. So 
much for idea as a material or organic modification. 

We must now, however, consider idea in reference to mind, i.e. as 
an object of consciousness. In this relation the fundamental not'ion 
to be attached to the term, as used by Descartes and the Cartesians, 
is that of a representative thought, or an object of consciousness) 
in and by the knowledge of which we become aware of something 
distinct from this object itself. Idea, Descartes says, is to be taken 
** pro omni re cogitata quatenus habet tantum esse objectivum in 
intellectu." — Diss, de Meth. P. iv. note. ** Idea est ipsa res cogitata 
quatenus est objective in intellectu." Again, idea is " cogitatio 
tanquam rei imago." — Cen. Med. iii. 97, and Works passim. De 
La Forge, De I'Esprit, chap. x. pp. 128, 131. 

It is necessary, however, with a view to an adequate under- 
standing of the Cartesian philosophy, to distinguish the two aspects 
under which the same idea was viewed by Descartes and his fol- 
lowers. The mental idea, while really one and indivisible, was 
considered in two logically distinct relations, viz., both as an object 
and as a medium of knowledge, that is, in reference to the mind 
knowing and the object known. This distinction is made by 
Descartes in several passages of the Meditations. Thus, " If ideas 
are taken in so far only as they are certain modes of consciousness, 
I do not remark any difference or inequality among them, and all 
seem in the same manner to proceed from myself; but considering 
them as images, of which one represents one thing and another a 
different, it is evident that a great diversity obtains among them." 
— Med. iii. p. 100. Preface of Med. p. 72. 

This distinction of idea as act and as representative object, 
pervades the whole body of Cartesian literature. Thus, to take 
an example, *' Every concept or idea," says Clauberg, " has a two- 
fold dependence : the one from the conceiving and thinking intellect, 
in as far as it is an act ; the other from the thing conceived or like, 
of which, to wit, it is the representation or image, or whence it is 
struck out by imitation. "—-Op. P. ii. p. 607 (Ed. 1691). Con. De 
la Forge, De I'Esprit, chap. x. pp. 128, 131. Flenderus, Logica 
Contracta Claubergiana (4th ed.) § 5, P- 12. 

Idea has thus with the Cartesians a twofold relation or dependence 
[realitas, perfectio, esse, dependentia). In so far as it is an act or 
mode of the mind {operatio mentis, intellectus), idea possesses a 
formal and proper being {esse formate seu proprium) ; in so far as 
it is the representation of the object thought {imago rei cogmtaice), 
or in the place of that object {in vice illus), it has an objective or 
vicarious being {esse objectivum sive vicarium). Agam, idea, as 
standing in this double relation or dependence, is said to have 
a twofold cause, viz., an efficient and an exemplary. In so far as 
a mode of consciousness, the idea has its efficient cause m intellect 
or in the mind itself {uti operans suae operattoms causa) ; m so far 
as representative, the object is the exemplary cause, standing m 
relation to the idea as the archetype to the ectype, the principal 
to the vicarious. ^ , ^. ^ 

It is the discrimination of idea as a mental operation or repre- 
sentative object, which affords the logical distinction of perception 
and idea, to be met with on all hands in Cartesian literature. By 
the term idea,'' says Descartes himself /' I .^^^erstand that form 
of any thought by the immediate perception of which I am conscious 
of that same thought."— Appendix, Def. 11. p. 229. 

*' I have said," says Amauld, " that I take perception and idea 



for the same thing. It should be observed, however, that this 
thing, although one, has two relations: the one to the mind which 
it modifies, the other to the thing perceived, in so far as it is objec- 
tively in the mind, and that the word perception more distinctly 
marks the former relation, and idea the latter. Thus, the perception 
of a square marks more directly my mind as perceiving a square; 
and the idea of a square marks more directly the square in so far 
as it is objectively in my mind." — Des Vraies et des Fausses Idees, 
chap. V. Def. 6. Con. De la Forge, De I'Esprit, chap. x. pp. 128, 

It should be observed, however, with regard to this distinction 
of idea and perception, that with Descartes perception is sometimes 
used where, in accordance with the propriety of language, we should 
have expected idea. Thus he says, " The mind always receives 
these (its perceptions) from the things represented by them.'* 
(De Pass., P. i. art. 17.) On the other hand, we find idea 
where, in accordance with his general nomenclature, we should 
have looked for perception. ** When I will and fear, because at 
the same time I perceive that I will and fear, the volition itself and 
fear are reckoned by me among ideas.'' — Ob. et Resp. Tertiae, Ob. v. 
p. 98 (Ed. 1670). 

Looking to ideas as the immediate objects of knowledge or per- 
ception, and considering them in relation to the faculties of which 
they are the objects, they may be classed as ideas of sense, of 
imagination, and of the pure intellect, in the exercise of each of 
which powers we are said to be apprehensive or percipient of ideas. 
But, as the objects of these powers, ideas differ both in their origin, 
and according to the character of the objects they represent. In 
the first relation, ideas arise either simply from the mind, as those 
of the pure intellect, or from the mind on occasion of body, modified 
by the corporeal species, as those of sense and imagination. Con- 
sidered as to their origin, the ideas of sense and imagination thus 
stand in contrast to those of the pure intellect, for in sense and 
imagination there is always a physical impression or corporeal 
species as the cause or occasion of the mental idea; whereas the 
intellect, as deriving its ideas from the mind itself, has no need of 
a material organ or of corporeal species. The ideas of sense and 
imagination, while they agree in being the result, though hyper- 
physically determined, of a physical antecedent in the form of the 
corporeal species, and thus in both depending on the bodily organ- 
ism, nevertheless differ in this, that the species to which the idea 
is attached is in the case of sense immediately dependent on the 
presence and action of external objects; while in imagination it 
depends only remotely on external objects, and proximately on the 
will, the memory, and the action of the animal spirits. 

But the chief contrast of ideas arises from the character of the 
objects they represent. In this relation, on the Cartesian doctrine, 
ideas fall into two great classes. The first comprehends all ideas 
of the individual and picturable, in other words, all the objects of 
sense and imagination; the second contains all our notions of the 
general, relative, or unpicturable — in other words, the ideas of the 
pure intellect. [Con. Med. vi. pp. 127-129; Prin. of Phil. P. i. 
§ 73. Lett. Ixxv., vol. iv. p. 318 of Garnier's ed., or vol. vi., L. Ixii. 
duod. ed. De la Forge, De I'Esprit, chap, xviii. pp. 298-302.) — 
Under sense it should be observed that idea, in the writings of 
Descartes as well as of others in the Cartesian school, denotes 
indifferently the apprehension of the primary and the sensations 

Notes 249 

of^the sec9ndary qualities of matter. Thus, Descartes speaks of 
the sensation or idea {sensus vel idea) of colour and heat Male- 
branche limited idea [tdee) to the apprehension of the primary 
reserving senhment to designate the sensations of the secondary 
qu^ities.— As the secondary qualities on their subjective side were 
held by the Cartesians t® be merely modifications of the percipient 
subject, and not to exist in nature as in consciousness, idea as 
applied to them (which was not generally the case out of the 
writings of Descartes), was not representative. Vide Prin. of Phil. 
P. i. §§ 69, 70, 71. 

III. OBJECTIVE REALITY — [realitos objecHva)—^. yy 

After what has been already said of the twofold relation of idea 
in the philosophy of Descartes, it is unnecessary to add much bv 
way of explanation of the term objective reality. This, as we have 
said, denotes that aspect of a representative thought in which it is 
considered in relation to the object represented; hence the object 
is said to possess objective reality in so far as it exists by represen- 
tation in thought [quatenus objicitur intellectui) . This use of the 
term objective, it will be remarked, is precisely opposed to the more 
modern (Kantian) acceptation of the same word, and corresponds, 
to a certain extent, with the counter-term subjective ; for objective 
reality [i.e.y the reality of representation) is in truth a subjective 

It may be of importance to note the two relations from which the 
representative reality of an idea is distinguished in Cartesian 
literature, with their appropriate designations. In the first place, 
the representative perfection (being) of an idea, was distinguished 
from the object of the idea in so far as it possessed an absolute 
existence, or existence independent of thought. In this relation 
the object was said to possess realitos actualis, formalis, as opposed 
to realitos objectiva. [Con. Med. iii. pp. 100, loi; Med. vi. p. 133.) 
The object as it exists in nature was by other philosophers, and 
among these by some of the Cartesians, called ens principale, reale, 
fundamentole {quasi fundomentum idece). 

In the second place, the representative being of an idea was 
distinguished from its relation to the mind of which it is the act, 
and in this aspect idea, so far as act, was said to possess esse reale, 
materiale, formate (q. forma qucedam- mentis, and this in contrast with 
objectivum), proprium ; in relation to the object represented, it 
was said to possess esse intentionale, formate (and this in contrast 
with materiale), objectivum, vicarium; these are the strictly con- 
trasted appellations. The esse objectivum was also called f^/)r^s^n- 
tativum, cognitum, in mente, tanquam in imagine, per tmttationem. 
Con, Claub. Op. P. ii. pp. 607-617. Hamilton's Reid, pp. 806, 807. 

IV. FROM OR THROUGH THE SENSES — {vel d scnsibus vcl per 
sensus) — ^p. 80 

*' From the senses, that is, from sight, by which I first perceived 
light, and then by its aid colours, figures, magnitudes, and an 
similar things; through the senses, that is, through hearing, in 
apprehending the words of men."— Claubergius, m h. loc. Op. 
P. ii. p. 1182. 

250 Notes 

V. THOUGHT — {cogitiUio, petisec ; cogitate, penser) — p. 82 

Thought {cogitatiOy pensee), is, in the Cartesian phraseology, 
applied to designate all that takes place within us, of which we are 
immediately conscious, i.e., all the modifications of the mind or 
thinking principle. Thought is thus but another term for conscious- 
ness, and embraces all the acts of the will, the intellect, the imagina- 
tion, and senses. — Med. iii. p. 97; Prin. of Phil. P. i. § 9; Resp. 
ad. Sec. Object. Def. i. (Appendix, p. 229). 

** Thought," says De la Forge, " I take for that perception, con- 
sciousness, or internal knowledge which each of us feels inmiediately 
by himself when he perceives what he does or what passes in him.** 
— De TEsprit, chap. iii. p. 14, chap. vi. p. 54. Amauld, Des Vraies 
et des Fausses Idees, chap, v., Def. i. 

" Mens," says Claubergius, " si vult cogitat, si non vult cogitat, 
si amat cogitat, si odit cogitat, si affirmat cogitat, si negat cogitat, 
si dubitat cogitat, si demonstrat cogitat, somniando cogitat, vigi- 
lando cogitat, sentiendo cogitat, imaginando cogitat, etc., atque 
ita in qualibet ejus functione cogitatio involvitur." — Op. P. ii. 
p. 600; P. i. p. 188; Log. P. i. § 102. 

Consciousness is thus, in the doctrine of the Cartesians, the general 
condition of our mental modifications, and in no way really distinct 
from the activities and passivities of which it is the condition. 
Though, in a sense already explained (as opposed to volition), 
perception is said to be contained under consciousness as its genus, 
they are yet nearly convertible terms. The difference between 
the two forms of expression seems to be, that thought, while 
embracing all the modifications of mind, whether volitions or per- 
ceptions, is not distinguished from the former as a passivity, while 
perception is. Thought, as thus denoting a mental modification 
both in its active and passive relation, marks the opposition and 
contrast of the modification to its negative, the extended, i.e., 
matter, while viewed as a perception the phaenomenon is regarded 
mainly in reference to its simple existence in consciousness, or as 
an apprehended property of mind. It seems to be in accordance 
with this view that the mind is uniformly spoken of as res cogitans 
(not percipiens) when opposed to its negative, the imthinking and 

VI. INNATE IDEAS — {idecB intuUa) — p. 98 

By innate idea, Descartes meant merely a mental modification 
which, existing in the mind antecedently to all experience, possesses, 
however, only a potential existence, until, on occasion of experience, 
it is called forth into actual consciousness. 

It is worthy of remark, in connection with the question of innate 
ideas, that the chief ground on which Descartes holds that certain 
of our judgments are prior to experience and native to the mind, 
is the impossibility of deriving them as universal from individual 
corporeal movements, which, if efi&cient, could give rise to modifi- 
cations merely individual. 

It will be seen, however, from the passages quoted below, and 
from a comparison of them with the passage quoted at pp. 198, 199, 
of these notes, that Descartes held a much wider doctrine of innate 
ideas than the modem, and one the principle of which could not 
iail sooner or later to result in the doctrine of Occasional Causes, 
to explain the connection between the corporeal antecedent, which 

Notes 251 

had no causal power, and the rise of the mental modification into 
actual consciousness. 

The following is the article (xii.) in the Programme of Regius 
which gave occasion to Descartes to make an explicit statement of 
his doctrine of innate ideas. 

\' Mens/* says Regius, " non indiget ideis, vel notionibus, vel 
axiomatibus innatis: sed sola ejus facultas cogitandi, ipsi, ad 
actiones suas peragendas, sufhcit." On this Descartes remarks: 
** In this article he (Regius) appears to differ from me merely in 
words; for when he says that the mind has no need of ideas, or 
notions, or axioms that are innate [or naturally impressed upon it], 
and meanwhile concedes to it a faculty of thinking (that is, a faculty 
natural to it or innate), he affirms my doctrine in effect, though 
denying it in word. For I have never either said or thought that 
the mind has need of innate (natural) ideas, which are anything 
different from its faculty of thinking; but when I remarked that 
there were in me certain thoughts which did not proceed from 
external objects, nor from the determination of my will, but from 
the faculty of thinking alone which is in me, that I might distinguish 
the notions or ideas, which are the forms of these thoughts, from 
others adventitious or factitious, I called them innate in the same 
sense in which we say that generosity is innate in certain families, 
in others certain diseases, as gout or gravel, not that, therefore, the 
infants ot those families labour under those diseases in the womb 
of the mother, but because they are born with a certain disposition 
or faculty of contracting them.'* 

Again, on art. xiii., he says — " What supposition is more absurd 
than that all the common notions which are in the mind arise from 
these corporeal motions, and cannot exist without them ? I should 
wish our author to show me what that co/poreal movement is which 
can form any common notion in our mind; for example, — that 
the things which are the same mith a third are the same with each 
other, or the like. For all those motions are particular ; but these 
notions are universal, and possess no affinity with motions, nor any 
relation to them.** 

'* He (Regius) proceeds, in article xiv., to affirm that the very 
idea of God which is in us arises not from our faculty of thinking, 
in which it is innate, but from divine revelation, or tradition, or the 
observation of things. We shall easily discover the error of this 
assertion, if we consider that a thing can be said to be from another, 
either because that other is its proximate and primary cause, or 
because it is simply the remote and accidental, which, in truth, 
gives occasion to the primary to produce its own effect at one time 
rather than at another. Thus, all workmen are the primary and 
proximate causes of their own works; but they who commission 
them, or offer payment for the execution of the works, are the 
accidental and remote causes, because the works would not perhaps 
have been done without the order. It cannot be doubted but that 
tradition or the observation of things is the remote cause, myiting 
us to attend to the idea of God which we possess, and to exhibit it 
in presence to our thought. But that it is the proximate cause 
(effectrix) of that idea can be alleged only by one who holds that 
we can know nothing of God beyond the word God, or the corporeal 
figure exhibited to us by painters in their representations ot God. 
Inasmuch as observation, if it be of sight, presents nothing of its 
own proper power to the mind except pictures, and Pictures whose 
whole v£u:iety is determined solely by that of certain corporea 

252 Notes 

movements, as our author himself teaches; if it be of hearing, 
observation presents nothing but words and sounds; if of the other 
senses, it presents nothing that can be related to God. And, indeed, 
it is manifest to every one that sight properly and by itself presents 
nothing except pictures, and hearing nothing but words or sounds; 
so that all which we think beyond these words or pictures, as the 
significates of them, are repressnted to us by ideas coming from 
no other source than our faculty of thinking, and therefore natural 
to it; that is, always existing in us in power. For to be in any 
faculty is not to be in act but in power only, because the very word 
faculty designates nothing but power.** — Lett, xxxviii., G£uniier's 
ed. tom. iv. Not. in Prog. Latin (1670), p. 175. 

** On the celebrated question (says De la Forge) as to whether the 
ideas of the mind are born with it, or acquired, I reply that they are 
both one and other. They are born with it, not only because it has 
never received them from the senses, but also because it is created 
with the faculty of thinking and forming them, which is the proxi- 
mate and principal cause of them; in the same way that we say 
gout or gravel is natural to certain families, when the members of 
them bring with them proximate dispositions to those maladies. 
But those ideas are acquired, and not natural, if by natural we 
understand that they are in the substance of the soul as in a con- 
servatory, in the manner in which pictures are disposed in a gallery, 
that we may consider them as we please ; for there is none of them 
in particular that needs to be actually present to our mind, which, 
being a thinking substance, can have nothing actually present to it 
of which it has no knowledge. It is for this reason they are con- 
tained in the mind only in power, and not in act'* — De I'Esprit, 
chap, x., pp. 143, 144. Con. Clauberg. on Med. iii., Op., P. i., 391. 

VII. FORMALLY AND EMINENTLY [formalUer, emtnenter) — p. 100 

Besides the application of the word formal already noticed, viz. 
(i), in opposition to objective, to denote the object as it exists in 
nature; and (2) as a synonym for objective in contrast to material. 
to denote the idea so far as it is a representation, there is still 
another use of the term in the writings of Descartes and in the 
Cartesian literature. In this third application, fermal is opposed 
to eminent, and refers to the relation of cause and effect. The 
contrast indicated by these terms in this relation is in regard to the 
manner in which a cause is said to contain its effect. A cause, as 
the sum of the perfection or reality of its effect, may contain this 
reality in either of two ways, and must in one of them. On the 
one hand, if the perfection of the effect be contained in the cause 
in the same mode in which it exists in the effect, or, if the cause be 
only possessed, in this respect, of equal perfection with the effect, 
the reality of the effect is said to be in the cause formally [formaliter, 
q. d. secundum eandem formam et rationem). Thus, the print of 
the foot has formally the quantity and figure of the foot, and is thus 
formally in its cause. In the same way, any absolute perfection is 
formally in God. On the other hand, if the effect be contained 
in the cause, not as it is in itself, or according to its intrinsic form, 
essence, or proper definition, but in a higher grade or mode of per- 
fection [gradu, modo eminentiori) , it is said to be in its cause emi- 
nently. In this sense the Divine intellect contains the human, 
since God knows, but without the imperfections incident to the 
exercise of our faculties of cognition. A cause containing eminently 

Notes 253 

thus contains all the reality of the effect more perfectly than the 
eflect itselt. This distinction, borrowed from the schoolmen has 
an important application, in the philosophy of Descartes to the 
question of the proof of the existence of God througli his' idea — 
Con. Med. 111., p. 41, etc. Appendix, Def. iv., p. 230; Ax. iv. p 2^^ 
Spinoza, Prin. Phil. Cart., P. i., vol. i., p. 16 (Paulus.). Cl'auberg. 
Exercit. vi., p. 613, §§ 5, 6 (Ed. 1691). Flender. Log., §50. 
Chauvm, Lex. Rat., voc. Continere. De Vries (Anti-Cart ) 
Exercit. vi., § 4, pp. 55, 56 (Ed. 1695). 

VIII. PURE INTELLECTION {intelUctio pura) — p. 178 
Intelligence, understanding [intellectus) , is the general name in 
Cartesian literature of the powers of cognition in contrast to those 
of will; and in this sense the term comprehends all the acts, 
whether of sense, memory, imagination, or of intellect proper! 
But intelligence has, besides its general, a special and restricted 
signification; and this especially when the qualifying epithet pure 
is joined with it. Pure intellection [intellectio pura) denotes not 
knowledge in general, but the knowledge, whether individual or 
general, of the mental phaenomena, and generally of all those objects 
we are capable of thinking in the narrower sense of the word, but 
cannot imagine, or hold up to our mind in an image or picture. In 
a word, with the Cartesians the pure imderstanding is the faculty 
of the unpicturable, imagination of the picturable. Whatever 
knowledge, therefore, we may be able to reach of mind or of God, 
— of body in its general relations, or in such of its properties as 
are either too great or too minute for apprehension by sense, — of 
those judgments which are native to the mind — falls within the 
province of the pure intellect. 

It should be observed that in this faculty, according to its appli 
cation, there is knowledge either without or with ideas — in other 
words, either an immediate or a mediate knowledge. It is by the 
pure intellect alone that we take cognisance of our own mind in 
its phaenomena, and these we can immediately, or without idea, 
apprehend. But of everything distinct from ourselves which we 
know by the intellect, we can have but a mediate knowledge, or a 
knowledge by idea. The distinction of the ideas of the imagination 
and the intellect is nearly similar to the distinction of thoughts 
into those of the individual and general, or of intuitions (in the 
older sense of the term), and notions or concepts. — Con. Note ii., 
Idea. Med. iv., p. 112. Med. vi., pp. 127-129. Prin. of Phil., 
§ 73. Lett. Ixxv., Gamier, tom. iv., p. 318 (or Ixii. of vol. vi. Ed. 
i2mo.). Ep. P. i., xxx. Reg. ad Direct. Ing., R. xii. De la Forge, 
De I'Esprit, chap, xviii., pp. 298-302. Hamilton's Reid, p. 291, 

IX. MOTION — p. 211 

The following section of the Principles is added to those given 
in the text, from its bearing logically and historically on the doctrine 
of Occasional Causes as arising out of Cartesianism : — 

'* That God is the primary cause of motion: and that he always 
preserves the same quantity of motion in the universe. 

'' After having thus adverted to the nature of motion, it is neces- 
sary to consider its cause, and that the twofold: firstly, the universal 
and primary, which is the general cause of all the motions in the 
world; and secondly, the particular, by which it happens that each 
of the parts of matter acquires the motion which it had not before. 

2 54 Notes 

And with respect to the general cause, it seems manifest to me that 
it is none other than God himself, who, in the beginning, created 
matter along with motion and rest, and now by his ordinary con- 
course alone preserves in the whole the same amount of motion and 
rest that he then placed in it. For although motion is nothing in 
the matter moved but its mode, it has yet a certain and determinate 
quantity, which we easily understand may remain always the same 
in the whole universe, although it changes in each of the parts of it. 
So that, in truth, we may hold, when a part of matter is moved with 
double the quickness of another, and that other is twice the size 
of the former, that there is just precisely as much motion, but no 
more, in the less body as in the greater; and that in proportion 
as the motion of any one part is reduced, so is that of some other 
and equal portion accelerated. We also know that there is per- 
fection in God, not only because he is in himself immutable, but 
because he operates in the most constant and immutable manner 
possible: so that with the exception of those mutations which 
manifest experience, or divine revelation renders certain, and which 
we perceive or believe are brought about without any change in 
the Creator, we ought to suppose no other in his works, lest there 
should thence arise ground for concluding inconstancy in God him- 
self. Whence it follows as most consonant to reason, that merely 
because God diversely moved the parts of matter when he first 
created them, and now preserves all that matter, manifestly in the 
same mode and on the same principle on which he first created it, 
he also always preserves the same quantity of motion in the matter 
itself."— Part ii. § 36. 


" Thus we may reckon upon having already discovered two 
diverse forms in matter, which may be taken for the forms of the 
first two elements of the visible world. The first is that of the 
scraping (raclure) which must have been separated from the other 
parts of matter, when they were rounded, and is moved with so 
much velocity that the force alone of its agitation is sufficient to 
cause it, in its contact with other bodies, to be broken and divided 
by them into an infinity of small particles that are of such a figure 
as always exactly to fill all the holes and small interstices which 
they find around these bodies. The other is, that of all the rest 
of the matter whose particles are spherical and very small in com- 
parison of the bodies we see on the earth, but nevertheless possess 
some determinate quantity, so that they can be divided into others 
much smaller: and we will still find in addition a third form in some 
parts of matter, to wit, in those which, on account of their size 
and figure, can not be so easily moved as the preceding; and I will 
endeavour to show that all the bodies of the visible world are 
composed of these three forms, which are found in matter, as of 
three diverse elements, to wit, that the sun and the fixed stars 
have the form of the first of these elements, the heavens that of the 
second, and the earth with the planets and comets that of the 
third. For since the sun and the fixed stars emit light, since the 
heavens transmit it, and since the earth, the planets, and comets 
reflect it, it appears to me I have ground for these three differences 
[luminousness, transparency, and opacity or obscurity, which are 
the chief we can relate to the sense of sight], in order to distinguish 
the three elements of the visible world." — Prin. of Phil, part iii., 
§ 52. Con. Chauvin, Lex. Rat., Art. Elementum. 



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