§ 114. The history of naturalism shows that, as in the case of life, so also in the case of _mind_, its hypotheses were projected by the Greeks, but precisely formulated and verified only in the modern period of science. In the philosophy of Democritus the soul was itself an atom, finer, rounder, and smoother than the ordinary, but thoroughly a part of the mechanism of nature. The processes of the soul are construed as interactions between the soul and surrounding objects. In sensation, the thing perceived produces images by means of effluxes which impinge upon the soul-atom. These images are not true reports of the outer world, but must be revised by thought before its real atomic structure emerges. For this higher critical exercise of thought Democritus devised no special atomic genesis. The result may be expressed either as the invalidity of such operations of mind as he could provide for in his universe, or the irreducibility to his chosen first principles of the very thought which defined them. Later naturalism has generally sacrificed epistemology to cosmology, and reduced thought to sensation. Similarly, will has been regarded as a highly developed case of instinct. Knowledge and will, construed as sensation and instinct, may thus be interpreted in the naturalistic manner within the field of biology. [Sidenote: Automatism.] § 115. But the actual content of sensation, and the actual feelings which attend upon the promptings of instinct, still stubbornly testify to the presence in the universe of something belonging to a wholly different category from matter and motion. The attitude of naturalism in this crucial issue has never been fixed and unwavering, but there has gradually come to predominate a method of denying to the inner life all efficacy and real significance in the cosmos, while admitting its presence on the scene. It is a strange fact of history that Descartes, the French philosopher who prided himself on having rid the soul of all dependence on nature, should have greatly contributed to this method. But it is perhaps not so strange when we consider that every dualism is, after all, symmetrical, and that consequently whatever rids the soul of nature at the same time rids nature of the soul. It was Descartes who first conceived the body and soul to be utterly distinct substances. The corollary to this doctrine was his _automatism_, applied in his own system to animals other than man, but which those less concerned with religious tradition and less firmly convinced of the soul's originating activity were not slow to apply universally. This theory conceived the vital processes to take place quite regardless of any inner consciousness, or even without its attendance. To this radical theory the French materialists of the eighteenth century were especially attracted. With them the active soul of Descartes, the distinct spiritual entity, disappeared. This latter author had himself admitted a