METAPHYSICAL STATUS OF FACTORS 233

studying the material world as physicists or the world of
experience as psychologists, the only articulate or com-
municable knowledge that we can attain is a knowledge of
structure. Let me add that, if this position be accepted,
the relation of matter and mind would lose much of its
mystery, for we should no longer be concerned with the
interactions of disparate substances but with the corre-
spondence of abstract structures.1

At the same time, to save misunderstanding, let me add that I
do not regard physical phenomena and psychological phenomena as
entirely on the same footing. Physical processes must be described,
and can only be described, in terms of relations and systems of
relations. But this is " because " (to quote a phrase used by John-
son in a somewhat similar context) " the ultimate constituents of
matter—if there are ultimate constituents—have, so to speak, no
insides." 2 The ultimate constituents of consciousness, on the other
hand, are c insides 5 that we know at first hand, even if that
knowledge is not as such directly communicable. General psycho-
logy, therefore, which includes introspective psychology, has to
take this further feature into account. Factorial psychology, being
concerned with the psychology of others, whose c insides' are not
directly known to us, must adopt a more contracted standpoint.
But these reservations are scarcely relevant to my main argument,
and are inserted only to forestall a possible criticism that their
omission might have provoked.

(c) On the Level of Empirical Science.—As a philosopher,
therefore, I should have no desire to shirk the deeper
problems of causality or the conception of the mind as an
ultimate entity or substance. But as a mere scientist I
have no right to express an opinion on such issues, much

1 This would simplify the problem of perception : for, although nothing
can resemble an idea except another idea, a material environment can corre-
spond to a perceptual continuum; like a map and a landscape, both may have
the same relational structure, and that is the only kind of ' resemblance ' we
require. Again, it would partly, elucidate the relation of brain to con-
sciousness : for the changing field of consciousness may correspond with the
changing field of cerebral tensions. Indeed, many of the problems of
Gestalt itself and of unconscious cerebration as well as of cognitive activity
could be very simply interpreted if we regarded the brain as a kind of organic
machine for continually solving matrix equations.

2 Johnson, W. E., Logic, Pt. Ill, p. xxiv.