216 THE FACTORS OF THE MIND

measurements, and to construct rigorous deductive argu-
ments in quantitative terms; all that interests him is to
know that the conclusions of those arguments can be verified:
never exactly—that he does not expect—but to a reasonably
close approximation.

Similarly, in psychology, if the question of existence is
to be pressed, I do not see why our factors should not be
entitled to the same kind of existence—or, if you will, the
same kind of non-existence—that is allowed to physical
forms of energy. Thomson would deny that general intel-
ligence exists as a real entity or as a genuine cause, but would
accept it as a symbolic way of describing the relations between
the ultimate neuronic elements; these alone he regards as
the real entities and the true causes. But his arguments,
so far as I can see, no more invalidate Spearman's main
position than the kinetic theory of heat precludes us from
talking of temperature as for all practical purposes * real,'
and treating it as a concrete existent whose amount (which
is also a sample or average) can be conveniently measured.

Intelligence I regard, not indeed as designating a special
form of energy, but rather as specifying certain individual
differences in the structure of the central nervous system—
differences whose concrete nature could be described in
histological terms.1 But in any case, whether it is a * real'

1 Spearman states that I identify g, not with intelligence, but with £ power
of attention * ([56], p. 88), and " ascribe individual differences of ability to
inequalities in ' power of attention ' " (p. 341). He supports his statement
by a paragraph taken from my first article ; but this paragraph was meant to
be interpreted in the light of the physiological hypothesis put forward in the
succeeding pages. In a suggestive book just published. Maxwell Garnett also
quotes the same passage, and seems at first sight to draw the same conclusion
(Knowledge and Character, 1940, pp. 144-5). And from time to time the
inference that " what we call intelligence is merely an effect of attention "
has been cited by teachers and by educational journals with approval.
Accordingly, since this notion has been so often attributed to me, I ought
perhaps to explain a little more fully my view of the relation between the
two.

Having shown (i) that a general factor enters into all cognitive processes
and (ii) that this general factor appears to be largely, if not wholly, inherited
or innate ([16], cf. [22]), I proposed to define intelligence as innate, general
cognitive efficiency ([20], p. 95) ; and then endeavoured to suggest an innate
and inheritable basis for this factor in the structure of the nervous system.