14

mately inorganic. The assimilation of the field of biology and physiology to the mechanical cosmos had made little real progress prior to the nineteenth century. Mechanical theories had, indeed, been projected in the earliest age of philosophy, and proposed anew in the seventeenth century.' Nevertheless, the structural and functional teleology of the organism remained as apparently irrefutable testimony to the inworking of some principle other than that of mechanical necessity. Indeed, the only fruitful method applicable to organic phenomena was that which explained them in terms of purposive adaptation. And it was its provision for a mechanical interpretation of this very principle that gave to the Darwinian law of natural selection, promulgated in 1859 in the

Origin of Species," so profound a significance for naturalism. It threatened to reduce the last stronghold of teleology, and completely to dispense with the intelligent Author of nature.

Darwin's hypothesis sought to explain the origin of animal species by survival under competitive conditions of existence through the possession of a structure suited to the environment. Only the

14 Harvey's discovery of the circulation of the blood, published in 1628, was regarded as a step in this direction.

most elementary organism need be presuppose together with slight variations in the course subsequent generations, and both may be conceive to arise mechanically. There will then result i surviving organisms a gradual accumulation o such variations as promote survival under the spe cial conditions of the environment. Such a principle had been suggested as early as the time of Empedocles, but it remained for Darwin to estab lish it with an unanswerable array of observation and experimentation. If any organism whatsoever endowed with the power of generation be allowed to have somehow come to be, naturalism now promises to account for the whole subsequent history of organic phenomena and the origin of any known species.

Mechanical

§ 113. But what of life itself? The question of the derivation of organic from inorganic matter has proved insoluble by direct means, Physiology. and the case of naturalism must here rest upon such facts as the chemical homogeneity of these two kinds of matter, and the conformity of physiological processes to more general physical laws. Organic matter differs from inorganic only through the presence of proteid, a peculiar product of known elements, which cannot be artificially

produced, but which is by natural means perpetually dissolved into these elements without any discoverable residuum. Respiration may be studied as a case of aerodynamics, the circulation of the blood as a case of hydrodynamics, and the heat given off in the course of work done by the body as a case of thermodynamics. And although vitalistic theories still retain a place in physiology, as do teleological theories in biology, on the whole the naturalistic programme of a reduction of organic processes to the type of the inorganic tends to prevail.

Mind.

The Reduction

§ 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 to Sensation. 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 emerge For this higher critical exercise of thought D mocritus devised no special atomic genesis. T result may be expressed either as the invalidity such operations of mind as he could provide fo in his universe, or the irreducibility to his chose first principles of the very thought which define them. Later naturalism has generally sacrifice: epistemology to cosmology, and reduced thought to sensation. Similarly, will has been regarded as i 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.

§ 115. But the actual content of sensation, and the actual feelings which attend upon the promptAutomatism. ings 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 department of the self, which he called the "passions," in which the course and content of mind is determined by bodily conditions. Extending this conception to the whole province of mind, they employed it to demonstrate the thorough-going subordination of mind