But, finally, some will object, “We can not live and work effectively under such a theory unless, indeed, we escape through pantheism.” It may, alas! be true that this view brings us too near Him in our sense of spiritual nakedness and shortcoming. It may, indeed, be that we can not live and work in the continual realized presence of the Infinite. It may, indeed, be that we must still wear the veil of a practical materialism on our hearts and minds. It may, indeed, be that in our practical life and scientific work we must still continue to think of natural forces as efficient agents. But, if so, let us at least remember that this attitude of mind must be regarded only as our ordinary work-clothes—necessary work-clothes it may be of our outer lower life—to be put aside when we return home to our inner higher life, religious and philosophical.
CHAPTER IV.
THE RELATION OF MAN TO NATURE.
There are two widely distinct views concerning the relation of man to Nature; the one as old as the history of human thought, the other only now urged upon us by modern science. According to the one, man is the counterpart and equivalent of Nature. He alone has—in fact is—an immortal spirit, and therefore he belongs to a world of his own. According to the other, man is but a part, a very insignificant part of Nature, and connected in the closest way with all other parts, especially with the animal kingdom. He has no world of his own, nor even kingdom of his own: he belongs to the animal kingdom. In that kingdom he has no department of his own: he is a vertebrate. In the department of vertebrates he has no privileged class of his own: he is a mammal. In the class of mammals he has no titled order of his own: he is a primate, and shares his primacy with apes. It is doubtful if he may enjoy the privacy of a family of his own—the Hominidæ—for the structural differences between man and the anthropoid apes are probably not so great as between the sheep family and the deer family.
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.
In recent times, physiology has made great and, to many, startling advances in the direction of connecting mental phenomena with brain-changes. Physiologists have established the correlation of vital with chemical and physical forces,[40] and probably in some sense, at least, of mental with vital forces. They have proved, in every act of perception, first a physical change in a nerve-terminal, then a propagated thrill along a nerve-fiber, and then a resulting change, physical or chemical, in the brain; and in every act of volition, a change first in a brain-cell, then, a return thrill along a nerve-fiber, and a resulting contraction of a muscle. Even the velocity of the transmission to and fro has been measured, and the time necessary to produce brain-changes estimated. They have also established the existence of physical and chemical changes in the brain corresponding to every change of mental state, and with great probability an exact quantitative relation between these changes of brain and the corresponding changes of mind. In the near future they may do more: they may localize all the different faculties and powers of the mind, each in its several place in the brain, and thus lay the foundations of a truly scientific phrenology. In the far-distant future we may possibly do much more. We may connect each kind of mental state with a different and distinctive kind of brain-change. We may find, for example, a right-handed rotation of atoms associated with love, and a left-handed rotation associated with hate, or a gentle sideways oscillation associated with consciousness, and a vertical pounding associated with will. Now, suppose all this, and even much more, be done in the way of associating, both in degree and in kind, mental changes with brain-changes. What then? “Why,” say the materialists, “we thereby identify mind with matter, mental forces with material forces. Thought, emotion, consciousness and will become products of the brain, in the same sense as bile is a product of the liver, or urea a product of the kidneys.”
Such is, in brief, the argument. Now, the answer: We may do all we have supposed and much more. We may push our knowledge in this direction as far as the boldest imagination can reach, and even then we are no nearer the solution of this mystery of the relation of brain-changes and mental changes than we are now. Even then it would be impossible for us to conceive how brain-changes produce mental changes or vice versa. Physical changes in sense-organs, transmitted along nerve-fibers, determine changes in brain-substance. So much is intelligible. But now there appear—how it is impossible to imagine—consciousness, thought, emotion, etc.—phenomena of an entirely different order, belonging to an entirely different world. So different, that it is impossible to imagine the nature of the nexus between, or to construe the one in terms of the other. Brain-cells are agitated and thought appears: Aladdin’s lamp is rubbed, and the genie appears. There is just as much intelligible causal relation between the two sets of phenomena in the one case as in the other.