Now it is evident that these two are only views from different points, psychical and structural. From the psychical point of view it is simply impossible to exaggerate the wideness of the gap that separates man from even the highest animals. From this point of view man must be set over as an equivalent, not only to the whole animal kingdom, but to the whole of Nature besides. From the structural point of view, on the contrary, it is impossible to exaggerate the closeness of the connection. Man’s body is identified with all Nature in its chemical constituents, with the body of all animals in its functions, with all vertebrates, especially mammals, in its structure. Bone for bone, muscle for muscle, ganglion for ganglion, almost nerve-fiber for nerve-fiber, his body corresponds with that of the higher animals. Whether he was derived from lower animals or not, certain it is that his structure even in the minutest details is precisely such as it would be if he were thus derived by successive slight modifications. Now, of these two views, the latter has been in recent times enormously productive in increasing our knowledge. Anatomy has become truly scientific only through comparative anatomy; physiology through comparative physiology; embryology through comparative embryology. Sociology is fast following in the same line, and becoming scientific through comparative sociology. Is not the same true also of psychology? Will not psychology become truly scientific only through comparative psychology, i. e., by the study of the spirit of man in relation to what corresponds to it in lower animals? But this view and this method, when pushed to what seems to many their logical conclusion, end in identification of man with mere animals, of spirit with mere physical and chemical forces, immortality with mere conservation of energy, and thus leads to blank and universal materialism. Thus, while it increases our knowledge, it destroys our hopes. Is there any escape? There is. The two extreme views given above are not irreconcilable. As already said, they are only views from different points, and therefore, although both true, are equally one-sided and partial, and a true and rational philosophy, in this as in all other cases of vexed questions, is found only in a higher view, which combines and reconciles these mutually excluding extremes. Can we find such a view? I think we can. Let us first, however, trace some of the stages of this scientific materialism. There are two main branches of the argument for materialism: one derived from _brain-physiology_, the other from _evolution_. As we wish to be perfectly fair, we will present and even press the argument in both these directions, although the latter alone bears directly on the subject in hand.