Primitive thinking about man is thus quite in line with primitive thinking about other things. In a way man's earliest philosophy of things is more coherent and more rigorously logical than that of modern times. The same principle is applied all round. All force is conceived as vital force; "souls" or "wills" govern all. The division between animate and inanimate things is of the vaguest possible character; that between man and animals can hardly be said to exist. Only very gradually do the distinctions between animate and inanimate, voluntary and involuntary actions, which are taken for granted by the modern mind, arise. And it is easy to conceive that in the growth of these distinctions, modes of thinking characteristic of primitive man, would linger longest in the always obscure field of psychology. Broadly, however, the growth of knowledge has consisted, as Huxley pointed out, in the substitution of a mechanical for a volitional interpretation of things. In one department after another purposeful action yields to inevitable causation. In physics, chemistry, geology, astronomy, and kindred sciences this process is now complete. The volitional interpretation still betrays a feeble vitality in biology; but even here the signs of an early demise are unmistakable. Its last stronghold is in psychology, and this because it is at once the newest of the sciences to be placed upon a positive basis, and also the most obscure in its ramifications. Yet there can be no reasonable doubt that the same principle which has been found to hold good in other directions will sooner or later be shown to obtain here also. Science is by its very nature progressive; and its progress is manifested by the degree to which phenomena hitherto unrelated are brought under constantly enlarging and more comprehensive generalisations. Men were once satisfied to explain the "wetness" of water as due to a spirit of "aquosity," the movement of the blood as due to a "certain spirit" dwelling in the veins and arteries. These were not statements of knowledge, but verbose confessions of ignorance. To this same class of belief belongs the "Free-Will" of the anti-determinist. It is the living representative of that immense family of souls and spirits with which early animistic thought peopled the universe. The surviving member of a once numerous family, it carries with it the promise of the same fate that has already overtaken its predecessors.