hypothesis of an equivalence between the psychical state and the
cerebral state imply a downright absurdity, as we have tried to prove in
a former essay,[110] but the facts, examined without prejudice,
certainly seem to indicate that the relation of the psychical to the
physical is just that of the machine to the screw. To speak of an
equivalence between the two is simply to curtail, and make almost
unintelligible, the Spinozistic or Leibnizian metaphysic. It is to
accept this philosophy, such as it is, on the side of Extension, but to
mutilate it on the side of Thought. With Spinoza, with Leibniz, we
suppose the unifying synthesis of the phenomena of matter achieved, and
everything in matter explained mechanically. But, for the conscious
facts, we no longer push the synthesis to the end. We stop half-way. We
suppose consciousness to be coextensive with a certain part of nature
and not with all of it. We are thus led, sometimes to an
"epiphenomenalism" that associates consciousness with certain particular
vibrations and puts it here and there in the world in a sporadic state,
and sometimes to a "monism" that scatters consciousness into as many
tiny grains as there are atoms; but, in either case, it is to an
incomplete Spinozism or to an incomplete Leibnizianism that we come
back. Between this conception of nature and Cartesianism we find,
moreover, intermediate historical stages. The medical philosophers of
the eighteenth century, with their cramped Cartesianism, have had a
great part in the genesis of the "epiphenomenalism" and "monism" of the
present day.

* * * * *

These doctrines are thus found to fall short of the Kantian criticism.
Certainly, the philosophy of Kant is also imbued with the belief in a
science single and complete, embracing the whole of the real. Indeed,
looked at from one aspect, it is only a continuation of the metaphysics
of the moderns and a transposition of the ancient metaphysics. Spinoza
and Leibniz had, following Aristotle, hypostatized in God the unity of
knowledge. The Kantian criticism, on one side at least, consists in
asking whether the whole of this hypothesis is necessary to modern
science as it was to ancient science, or if part of the hypothesis is
not sufficient. For the ancients, science applied to _concepts_, that is
to say, to kinds of _things_. In compressing all concepts into one, they
therefore necessarily arrived at a _being_, which we may c