II. WHEN Auguste Comte proclaimed the, passing of metaphysics and the coming of positive science, the positivity which he claimed for science depended on two presuppositions-first, that the independent existence of the physical universe is unquestionable, and second, that the authority of reason is unchallengeable. The principle of relativity has questioned the first, the theory of creative evolution has challenged the second. The two theories may seem to be quite disconnected, but when we consider the complete revolution which the fundamental concepts of science have undergone since they were formulated, they are seen to be very closely related. The first concerns the relation of philosophy to physics; the second, with which this article deals, concerns the relation of philosophy to biology and psychology.