The third conception recommends itself to many on account of its greater simplicity. Formulated as the doctrine of monism, it states that the mind and its material basis are merely different aspects of one and the same thing, and that there is only one series of connected elements which are known to us directly as the current of our thoughts and indirectly as the physiological processes going on mainly in the cerebrum. Thus mind is purely subjective, the brain is only mediately objective. It is because the mental and the material are so intimately related that the monist believes them to be connected as are the lungs and respiration, the hand and grasping, or the eye and the reception of visual impressions from without.
But whichever one of these explanations we choose to adopt as our own, the basic fact of primary importance is that there is an invariable dependence of human thought upon a brain comprising a highly developed cerebrum, whatever may be the ultimate nature of the way mental processes are determined by physical processes, or vice versa. This fact stands unquestioned and unassailable; human faculty and the brain cannot be considered apart, even if they may not actually be different aspects of the same basic "mind-stuff," as Clifford calls the ultimate dual thing.
Like all of the other organs of lesser importance belonging to the nervous system, the brain is a complex of tissues which in the last analysis are groups of cell-bodies with their fibrous prolongations. When these cellular elements are in operation, mental processes go on; the unit of the mental process therefore is the functioning of a brain-cell. But we know that the substance of a brain-cell is the wonderful physical basis of life called protoplasm, that demanded our attention at the outset. The chemicals that go to make up protoplasm are everywhere carbon, hydrogen, oxygen, and other substances that are exactly the same outside the body as inside. It is the combination of these substances in a peculiar way which makes protoplasm, and it is the combination of their individual properties which in a real even though unknown manner gives the powers to protoplasm, even to that of a living brain-cell. Does science teach us, then, that the ultimate elements of human faculty are carbon-ness and hydrogen-ness, and oxygen-ness, which in themselves are not mind, but which when they are combined, and when such chemical atoms exist in protoplasm, constitute mental powers? Plain common-sense answers in the affirmative. We need not, indeed, we must not, attribute mind as such to rock salt or to the water of a stream, but we do know that salts and water and other dead substances may enter into the composition of the material brain which is the physical basis of mind.
In my opinion the individual argument renders the monistic conception of mind and matter unassailable. The food that we may eat and the water we may drink are dead, and as such they display absolutely no evidence of nervous or mental processes. When they enter our bodies, they with other foods replenish the various tissues, and among these the parts of the brain. In a material sense they become actual living protoplasm, replacing the worn-out substances destroyed during our previous thinking; and their properties are combined to make brain and thought, to play for a time their part in life, and to pass back into the world of dead, unthinking things. Every one of us knows that hunger reduces our ability to think clearly and fully, and every one knows also that mental vigor is renewed when fresh supplies of nourishment reach the brain. What can be the source of mentality, if it is not something brought in from the outer world along with the chemical substances which taken singly are devoid of mind? Scientific monism frankly replies that it is unable to find another origin.
We are thus brought to recognize, not only the continuity taught by organic evolution, but also the uniformity of the materials constituting the entire sensible world, inasmuch as the ultimate unit of all nervous phenomena is the reflex act of a protoplasmic mass, which itself is a synthesis of properties inhering in the chemical elements making up living matter. Among inorganic things the mind-stuff units are combined in relatively simple ways, and the "stuff" does not give any outward evidences of "mind" as such. Living things are almost infinitely complex as regards their chemical organization, and even in the very lowest of them we can discern a cell-reflex element which, combined with others like it, forms the unit of the compounds we call instinct, intelligence, and reason. Hence through an analysis of mental evolution we are enabled to form the larger conception of a continuous universe whose ultimate elements are the same everywhere.
VII
SOCIAL EVOLUTION AS A BIOLOGICAL PROCESS
We now reach a critical juncture in our study of the foundations of evolutionary doctrine, for we must pass at this point to an inquiry into the nature and origin of human social relations. In undertaking this task we may seem to leave the field which is properly that of organic evolution, and many perhaps will be unwilling to view such aspects of human life as materials for purely biological analysis, arrangement, and explanation. But even before the reasons for doing so may be made apparent, every one must admit that the subject of mental evolution, which comprises so large a bulk of details expressly social in their character and value, virtually compels us to scrutinize the history of the economic and other interrelationships maintained by the human constituents of civilized, barbarous, and savage communities. Language has been treated as an individual mental product, and so have the arts of life and of pleasure; but all of these things find their greatest utility in their social usage,—in their value as bonds which hold together the few or many human beings composing groups of lower or higher grade. Without discovering any other reasons we would be impelled to take up social evolution, for this process is inextricably bound up with the origin and development of all departments of human thought and action.
If now this new field is actually to be included within the scope of the laws controlling the rest of nature's evolution, two general conclusions must be established. Although no formal order need be followed, it must at some time be shown that human social relations are biological relations, to be best explained only through their comparison with the far simpler modes of association found by the biologist among lower orders of beings; and in the second place it must be demonstrated that identical biological laws, uniform in their operation everywhere in the organic world, have controlled the origin and establishment of even the most complex societies of men. So far no reason has been discovered by science for believing that evolution has been discontinuous, holding true only for the merely physical characteristics of humanity as a whole; and furthermore, the impersonal student of nature finds ample positive evidences showing that the basic laws of associations of whatever grade are exactly the same. For these laws we are to seek.
Heretofore the doctrine of organic evolution has been discussed with reference to the single individual organism viewed as a natural object whose history and vital relations require elucidation. Both in the general arguments of the first few chapters and in the fifth and sixth chapters dealing with the single case of the human species, the proof has been given that all of the structural and physiological characters of any and every organic type fall within the scope of the principles of evolution, by which alone they can be reasonably interpreted. It has been unjust in a sense to ignore completely the importance of the organic relations of a social nature to which we are now to turn, because no individual can exist without having its life directly influenced, not only by other kinds of organisms, but even more intimately by other members of its own species. In a single day's activity we who are citizens of a great metropolis are forced into contact with almost countless other lives, glancing off from one and another after influencing them to some degree, and gaining ourselves some impetus and stimulus from our longer or shorter intercourse with each of them. Our varied social relations are so many and obvious that it is quite superfluous to specify them as essential things in human life. For the very reason that they are so obvious and constitute so large a part of our daily life, we are in danger of conceiving them to be exclusively human; we unconsciously regard them as different from anything to be found elsewhere and quite independent of the biological laws controlling the human unit.