We might just as well recognise facts first as last, for they will have to be recognised some time. Truths are not put down by inhospitality—they are simply put off. The universe has a policy, a program. We may close our eyes to the facts around us, hoping in this way to compel them to pass away or be forgotten. But they do not pass away, nor will they be forgotten. They simply become invisible. They will live on and present themselves to other minds or ages or climes more hospitable or honest than our own. The only proper attitude of mind to assume toward the various doctrines existing among men is the attitude of perfect willingness to believe anything—anything that appeals to us as being reasonable and right. The great majority of men, however, are intellectual solids—unable to move and unwilling to think. They have certain beliefs to which they are determined to hold on, and everything that does not fit in with these beliefs is rejected as a matter of course.
II. Evidences of Psychical Evolution.
That mind has evolved, and that there is a psychical kinship, an actual consanguinity of feelings and ideas, among all the forms of animal life is proved incontestably by the following facts:
1. The evolution of mind is implied by the fact of the evolution of structures. ‘I hold,’ says Romanes, in the introduction to his great work on ‘Mental Evolution,’ ‘that, if the doctrine of organic evolution is accepted, it carries with it, as a necessary corollary, the doctrine of mental evolution.’ It makes no difference what theory we adopt regarding the essential natures of the physical and the psychical—whether we agree with the materialist that mind is an attribute of matter, with the idealist that matter is a creation of mind, with the monist that mind and body are only different aspects of the same central entity, or with the dualist that body and soul are two distinct but temporarily dependent existences—we must in any case recognise the fact, which is perceived by all, that there is an ever-faithful parallel between the neural and psychical phenomena of every organism. And if the elements which enter into and make up the physical structure of man have been derived from, and determined by, preceding forms of life, the elements which enter into and make up the psychical counterpart of the physical have also, without any doubt, been inherited from, and determined by, ancestral life forms.
2. Closely allied to the foregoing reason for a belief in the evolution of mind is that derived from a comparative survey of the nervous system in man and other animals. In man, mind is closely associated with a certain tissue or system of tissues—nerve tissue or the nervous system. That mind is correlated with nerve structure, and that mental anatomy may be learned from a study of the anatomy of the nervous system, especially of the brain, is the basic postulate of the science of physiological psychology. Now, nerve cells exist in all animals above the sponge, and a comparatively well-developed nervous system is found even among many of the invertebrates, as the higher worms, crustaceans, insects, and mollusks. The nervous system of invertebrates, though composed of the same kind of tissue, is constructed according to a somewhat different plan of architecture from that of the vertebrates. But in all of the great family of backboned animals the nervous system is built on the same general plan as in man, with a cerebro-spinal trunk extending from the head along the back and motory and sensory nerves ramifying to all parts of the body. There is also a sympathetic nervous system in all animals down as far as the insects. The brain, which is the most important part of the nervous system, and which has been called the ‘organ of consciousness,’ presents throughout the animal kingdom, from its beginning in the worms to man, a graduated series of increasing complication proceeding out of the same fundamental type. This is especially true of the vertebrates. Fishes, amphibians, reptiles, birds, and mammals, all have in their brains the same primary parts, the same five fundamental divisions, as are found in the brain of man. Hence, whatever may be thought about the mental states of invertebrates, we have the right, in the case of the vertebrate orders of life, to infer, from the general similarity of their nervous system to our own, that they have a corresponding similarity to ourselves in mental constitution and experience.
3. The evolution of mind is suggested by the existence in the animal world of all grades of intelligence, from almost mindless forms to forms even exceeding in some respects the mental attainments of men. The jelly-fish and the philosopher are not mental aliens. They are linked to each other by a continuous gradation of intermediate intelligences. The existence of these grades of mental development suggest psychical evolution and kinship, just as the existence of like grades of structural development suggest physical evolution.
4. In the mental life of animals the same factors of evolution exist as those by means of which organic structures have been brought into existence, and it is reasonable to suppose that the operation of these factors have produced in the mental world results analogous to those produced by the operation of the same factors among organic structures.
Men and other animals vary in their natures and mental faculties quite as much as they do in colour, size, and shape. It is commonly supposed that the mental and temperamental variety existing among individual men does not exist among individual birds, quadrupeds, insects, etc. But a little observation or reflection ought to be enough to convince anyone that such a supposition belongs to that batch of pre-Darwinian mistakes presented to us by an over-generous past. We are not acquainted with the inhabitants of our fields and barn-yards. We are almost as ignorant of the mental life and personality of these door-yard neighbours and friends of ours as we would be if they were the inhabitants of another continent. That is why our obtuse minds lump them together so indiscriminately—we do not know anything about them. We never take the trouble, or think it worth while, to get acquainted with them, much less to study and know them. We have grown up in the falsehood that they are altogether different from what we are, and that it is really not worth while to bother our gigantic heads about them, except to use them when it comes handy, or kick them to one side, or execute them, when they get in the way. Everybody else looks at the matter in about the same way, so we just let it go at that.
There is a sameness about foreigners and other classes of human beings with whom we are but slightly, or not at all, acquainted, until we come to know them and can discriminate one from another. I remember once asking my sister, if her baby, which looked to me like all other babies I had ever seen, were mixed up with a lot of other babies of about the same age, whether she could pick hers out from all the rest, and she gave me an unmistakable affirmative by answering, ‘What a foolish question!’
There is less variety among the individuals of non-human races than among individual men, just as there is less variety among individual savages than among the members of a civilised community. But there is mental diversity among all beings, and we only need to whittle our observation a little to recognise the fact. You never hear the keeper of a menagerie or any intelligent associate of dogs, horses, birds, or insects say there is no individuality among these animals. Brehm, the great German naturalist, assures us that each individual monkey of all those he kept tame in Africa had its own peculiar temper and disposition. And this is no more than what everyone who knows anything about it knows to be true of dogs, horses, cats, cattle, birds, and even fishes and insects. Any intelligent dog-fancier or pigeon-fancier can tell you the personal peculiarities of every one of the fifty or a hundred dogs or pigeons in his charge. He has watched and studied them since they came into existence, and through this continuous association he has come to know them. He simply makes discriminations that are not made by the casual or superficial observer. The Laplander knows and names each reindeer in his herd, though to a stranger they are all as much alike as the multitudes on an ant-hill. The Peckhams of Milwaukee, those indefatigable investigators of spiders and insects, are constantly telling us of the wonderful individuality possessed by these lowly lessees of our fields and gardens. In their work on ‘The Habits and Instincts of the Solitary Wasps,’ speaking of the ammophiles, these authors say: ‘In this species, as in every one that we have studied, we have found a most interesting variation among the different individuals, not only in methods, but in character and intellect. While one was beguiled from her hunting by every sorrel blossom she passed, another stuck to her work with indefatigable perseverance. While one stung her caterpillars so carelessly and made her nest in so shiftless a way that her young could survive only through some lucky chance, another devoted herself to these duties not only with conscientious earnestness, but with an apparent craving after artistic perfection that was touching to see.’ The variation in the mental phenomena of animals, including man, is partly innate, and partly the result of environment or education.