The Destiny of Man.

by John Fiske.

PREFACE.

Having been invited to give an address before the Concord School of Philosophy this summer, upon some subject relating to the question of immortality there under discussion, it seemed a proper occasion for putting together the following thoughts on the origin of Man and his place in the universe. In dealing with the unknown, it is well to take one"s start a long way within the limits of the known. The question of a future life is generally regarded as lying outside the range of legitimate scientific discussion. Yet while fully admitting this, one does not necessarily admit that the subject is one with regard to which we are forever debarred from entertaining an opinion. Now our opinions on such transcendental questions must necessarily be affected by the total ma.s.s of our opinions on the questions which lie within the scope of scientific inquiry; and from this point of view it becomes of surpa.s.sing interest to trace the career of Humanity within that segment of the universe which is accessible to us. The teachings of the doctrine of evolution as to the origin and destiny of Man have, moreover, a very great speculative and practical value of their own, quite apart from their bearings upon any ultimate questions. The body of this essay is accordingly devoted to setting forth these teachings in what I conceive to be their true light; while their transcendental implications are reserved for the sequel.

As the essay contains an epitome of my own original contributions to the doctrine of evolution, I have added at the end a short list of references to other works of mine, where the points here briefly mentioned are more fully argued and ill.u.s.trated. The views regarding the progress of human society, and the elimination of warfare, are set forth at greater length in a little book now in the press, and soon to appear, ent.i.tled "American Political Ideas."

PETERSHAM, September 6, 1884.

THE DESTINY OF MAN.

I.

Man"s Place in Nature, as affected by the Copernican Theory.

When we study the Divine Comedy of Dante--that wonderful book wherein all the knowledge and speculation, all the sorrows and yearnings, of the far-off Middle Ages are enshrined in the glory of imperishable verse--we are brought face to face with a theory of the world and with ways of reasoning about the facts of nature which seem strange to us to-day, but from the influence of which we are not yet, and doubtless never shall be, wholly freed. A cosmology grotesque enough in the light of later knowledge, yet wrought out no less carefully than the physical theories of Lucretius, is employed in the service of a theology c.u.mbrous in its obsolete details, but resting upon fundamental truths which mankind can never safely lose sight of. In the view of Dante and of that phase of human culture which found in him its clearest and sweetest voice, this earth, the fair home of man, was placed in the centre of a universe wherein all things were ordained for his sole behoof: the sun to give him light and warmth, the stars in their courses to preside over his strangely checkered destinies, the winds to blow, the floods to rise, or the fiend of pestilence to stalk abroad over the land,--all for the blessing, or the warning, or the chiding, of the chief among G.o.d"s creatures, Man. Upon some such conception as this, indeed, all theology would seem naturally to rest. Once dethrone Humanity, regard it as a mere local incident in an endless and aimless series of cosmical changes, and you arrive at a doctrine which, under whatever specious name it may be veiled, is at bottom neither more nor less than Atheism.

On its metaphysical side Atheism is the denial of anything psychical in the universe outside of human consciousness; and it is almost inseparably a.s.sociated with the materialistic interpretation of human consciousness as the ephemeral result of a fleeting collocation of particles of matter. Viewed upon this side, it is easy to show that Atheism is very bad metaphysics, while the materialism which goes with it is utterly condemned by modern science.[1] But our feeling toward Atheism goes much deeper than the mere recognition of it as philosophically untrue. The mood in which we condemn it is not at all like the mood in which we reject the corpuscular theory of light or Sir G.C. Lewis"s vagaries on the subject of Egyptian hieroglyphics. We are wont to look upon Atheism with unspeakable horror and loathing. Our moral sense revolts against it no less than our intelligence; and this is because, on its practical side, Atheism would remove Humanity from its peculiar position in the world, and make it cast in its lot with the gra.s.s that withers and the beasts that perish; and thus the rich and varied life of the universe, in all the ages of its wondrous duration, becomes deprived of any such element of purpose as can make it intelligible to us or appeal to our moral sympathies and religious aspirations.

And yet the first result of some of the grandest and most irrefragable truths of modern science, when newly discovered and dimly comprehended, has been to make it appear that Humanity must be rudely unseated from its throne in the world and made to occupy an utterly subordinate and trivial position; and it is because of this mistaken view of their import that the Church has so often and so bitterly opposed the teaching of such truths. With the advent of the Copernican astronomy the funnel-shaped Inferno, the steep mountain of Purgatory crowned with its terrestrial paradise, and those concentric spheres of Heaven wherein beatified saints held weird and subtle converse, all went their way to the limbo prepared for the childlike fancies of untaught minds, whither Hades and Valhalla had gone before them. In our day it is hard to realize the startling effect of the discovery that Man does not dwell at the centre of things, but is the denizen of an obscure and tiny speck of cosmical matter quite invisible amid the innumerable throng of flaming suns that make up our galaxy. To the contemporaries of Copernicus the new theory seemed to strike at the very foundations of Christian theology. In a universe where so much had been made without discernible reference to Man, what became of that elaborate scheme of salvation which seemed to rest upon the a.s.sumption that the career of Humanity was the sole object of G.o.d"s creative forethought and fostering care? When we bear this in mind, we see how natural and inevitable it was that the Church should persecute such men as Galileo and Bruno. At the same time it is instructive to observe that, while the Copernican astronomy has become firmly established in spite of priestly opposition, the foundations of Christian theology have not been shaken thereby. It is not that the question which once so sorely puzzled men has ever been settled, but that it has been outgrown. The speculative necessity for man"s occupying the largest and most central spot in the universe is no longer felt. It is recognized as a primitive and childish notion. With our larger knowledge we see that these vast and fiery suns are after all but the t.i.tan like _servants_ of the little planets which they bear with them in their flight through the abysses of s.p.a.ce. Out from the awful gaseous turmoil of the central ma.s.s dart those ceaseless waves of gentle radiance that, when caught upon the surface of whirling worlds like ours, bring forth the endlessly varied forms and the endlessly complex movements that make up what we can see of life. And as when G.o.d revealed himself to his ancient prophet He came not in the earthquake or the tempest but in a voice that was still and small, so that divine spark the Soul, as it takes up its brief abode in this realm of fleeting phenomena, chooses not the central sun where elemental forces forever blaze and clash, but selects an outlying terrestrial nook where seeds may germinate in silence, and where through slow fruition the mysterious forms of organic life may come to take shape and thrive. He who thus looks a little deeper into the secrets of nature than his forefathers of the sixteenth century may well smile at the quaint conceit that man cannot be the object of G.o.d"s care unless he occupies an immovable position in the centre of the stellar universe.

II.

Man"s Place in Nature, as affected by Darwinism.

When the Copernican astronomy was finally established through the discoveries of Kepler and Newton, it might well have been p.r.o.nounced the greatest scientific achievement of the human mind; but it was still more than that. It was the greatest revolution that had ever been effected in Man"s views of his relations to the universe in which he lives, and of which he is--at least during the present life--a part. During the nineteenth century, however, a still greater revolution has been effected. Not only has Lyell enlarged our mental horizon in time as much as Newton enlarged it in s.p.a.ce, but it appears that throughout these vast stretches of time and s.p.a.ce with which we have been made acquainted there are sundry well-marked changes going on. Certain definite paths of development are being pursued; and around us on every side we behold worlds, organisms, and societies in divers stages of progress or decline. Still more, as we examine the records of past life upon our globe, and study the mutual relations of the living things that still remain, it appears that the higher forms of life--including Man himself--are the modified descendants of lower forms. Zoologically speaking, Man can no longer be regarded as a creature apart by himself.

We cannot erect an order on purpose to contain him, as Cuvier tried to do; we cannot even make a separate family for him. Man is not only a vertebrate, a mammal, and a primate, but he belongs, as a genus, to the catarrhine family of apes. And just as lions, leopards, and lynxes--different genera of the cat-family--are descended from a common stock of carnivora, back to which we may also trace the pedigrees of dogs, hyaenas, bears, and seals; so the various genera of platyrrhine and catarrhine apes, including Man, are doubtless descended from a common stock of primates, back to which we may also trace the converging pedigrees of monkeys and lemurs, until their ancestry becomes indistinguishable from that of rabbits and squirrels. Such is the conclusion to which the scientific world has come within a quarter of a century from the publication of Mr. Darwin"s "Origin of Species;" and there is no more reason for supposing that this conclusion will ever be gainsaid than for supposing that the Copernican astronomy will some time be overthrown and the concentric spheres of Dante"s heaven reinstated in the minds of men.

It is not strange that this theory of man"s origin, which we a.s.sociate mainly with the name of Mr. Darwin, should be to many people very unwelcome. It is fast bringing about a still greater revolution in thought than that which was heralded by Copernicus; and it naturally takes some time for the various portions of one"s theory of things to become adjusted, one after another, to so vast and sweeping a change.

From many quarters the cry goes up,--If this be true, then Man is at length cast down from his high position in the world. "I will not be called a mammal, or the son of a mammal!" once exclaimed an acquaintance of mine who perhaps had been brought up by hand. Such expressions of feeling are crude, but the feeling is not unjustifiable. It is urged that if man is physically akin to a baboon, as pigs are akin to horses, and cows to deer, then Humanity can in nowise be regarded as occupying a peculiar place in the universe; it becomes a mere incident in an endless series of changes, and how can we say that the same process of evolution that has produced mankind may not by and by produce something far more perfect? There was a time when huge bird-like reptiles were the lords of creation, and after these had been "sealed within the iron hills" there came successive dynasties of mammals; and as the iguanodon gave place to the great Eocene marsupials, as the mastodon and the sabre-toothed lion have long since vanished from the scene, so may not Man by and by disappear to make way for some higher creature, and so on forever? In such case, why should we regard Man as in any higher sense the object of Divine care than a pig? Still stronger does the case appear when we remember that those countless adaptations of means to ends in nature, which since the time of Voltaire and Paley we have been accustomed to cite as evidences of creative design, have received at the hands of Mr.

Darwin a very different interpretation. The lobster"s powerful claw, the b.u.t.terfly"s gorgeous tints, the rose"s delicious fragrance, the architectural instinct of the bee, the astonishing structure of the orchid, are no longer explained as the results of contrivance. That simple but wasteful process of survival of the fittest, through which such marvellous things have come into being, has little about it that is a.n.a.logous to the ingenuity of human art. The infinite and eternal Power which is thus revealed in the physical life of the universe seems in nowise akin to the human soul. The idea of beneficent purpose seems for the moment to be excluded from nature, and a blind process, known as Natural Selection, is the deity that slumbers not nor sleeps. Reckless of good and evil, it brings forth at once the mother"s tender love for her infant and the horrible teeth of the ravening shark, and to its creative indifference the one is as good as the other.

In spite of these appalling arguments the man of science, urged by the single-hearted purpose to ascertain the truth, be the consequences what they may, goes quietly on and finds that the terrible theory must be adopted; the fact of man"s consanguinity with dumb beasts must be admitted. In reaching this conclusion, the man of science reasons upon the physical facts within his reach, applying to them the same principles of common-sense whereby our everyday lives are successfully guided; and he is very apt to smile at the methods of those people who, taking hold of the question at the wrong end, begin by arguing about all manner of fancied consequences. For his knowledge of the history of human thinking a.s.sures him that such methods have through all past time proved barren of aught save strife, while his own bold yet humble method is the only one through which truth has ever been elicited. To pursue unflinchingly the methods of science requires dauntless courage and a faith that nothing can shake. Such courage and such loyalty to nature brings its own reward. For when once the formidable theory is really understood, when once its implications are properly unfolded, it is seen to have no such logical consequences as were at first ascribed to it. As with the Copernican astronomy, so with the Darwinian biology, we rise to a higher view of the workings of G.o.d and of the nature of Man than was ever attainable before. So far from degrading Humanity, or putting it on a level with the animal world in general, the Darwinian theory shows us distinctly for the first time how the creation and the perfecting of Man is the goal toward which Nature"s work has all the while been tending.

It enlarges tenfold the significance of human life, places it upon even a loftier eminence than poets or prophets have imagined, and makes it seem more than ever the chief object of that creative activity which is manifested in the physical universe.

III.

On the Earth there will never be a Higher Creature than Man.

In elucidating these points, we may fitly begin by considering the question as to the possibility of the evolution of any higher creature than Man, to whom the dominion over this earth shall pa.s.s. The question will best be answered by turning back and observing one of the most remarkable features connected with the origin of Man and with his superiority over other animals. And let it be borne in mind that we are not now about to wander through the regions of unconditional possibility. We are not dealing with vague general notions of development, but with the scientific Darwinian theory, which alleges development only as the result of certain rigorously defined agencies.

The chief among these agencies is Natural Selection. It has again and again been ill.u.s.trated how by the c.u.mulative selection and inheritance of slight physical variations generic differences, like those between the tiger and the leopard, or the cow and the antelope, at length arise; and the guiding principle in the acc.u.mulation of slight physical differences has been the welfare of the species. The variant forms on either side have survived while the constant forms have perished, so that the lines of demarcation between allied species have grown more and more distinct, and it is usually only by going back to fossil ages that we can supply the missing links of continuity. In the desperate struggle for existence no peculiarity, physical or psychical, however slight, has been too insignificant for natural selection to seize and enhance; and the myriad fantastic forms and hues of animal and vegetal life ill.u.s.trate the seeming capriciousness of its workings. Psychical variations have never been unimportant since the appearance of the first faint pigment-spot which by and by was to translate touch into vision, as it developed into the lenses and humours of the eye.[2] Special organs of sense and the lower grades of perception and judgment were slowly developed through countless ages, in company with purely physical variations of shape of foot, or length of neck, or complexity of stomach, or thickness of hide. At length there came a wonderful moment--silent and unnoticed, as are the beginnings of all great revolutions. Silent and unnoticed, even as the day of the Lord which cometh like a thief in the night, there arrived that wonderful moment at which psychical changes began to be of more use than physical changes to the brute ancestor of Man. Through further ages of ceaseless struggle the profitable variations in this creature occurred oftener and oftener in the brain, and less often in other parts of the organism, until by and by the size of his brain had been doubled and its complexity of structure increased a thousand-fold, while in other respects his appearance was not so very different from that of his brother apes.[3]

Along with this growth of the brain, the complete a.s.sumption of the upright posture, enabling the hands to be devoted entirely to prehension and thus relieving the jaws of that part of their work, has cooperated in producing that peculiar contour of head and face which is the chief distinguishing mark of physical Man. These slight anatomical changes derive their importance entirely from the prodigious intellectual changes in connection with which they have been produced; and these intellectual changes have been acc.u.mulated until the distance, psychically speaking, between civilized man and the ape is so great as to dwarf in comparison all that had been achieved in the process of evolution down to the time of our half-human ancestor"s first appearance. No fact in nature is fraught with deeper meaning than this two-sided fact of the extreme physical similarity and enormous psychical divergence between Man and the group of animals to which he traces his pedigree. It shows that when Humanity began to be evolved an entirely new chapter in the history of the universe was opened. Henceforth the life of the nascent soul came to be first in importance, and the bodily life became subordinated to it. Henceforth it appeared that, in this direction at least, the process of zoological change had come to an end, and a process of psychological change was to take its place. Henceforth along this supreme line of generation there was to be no further evolution of new species through physical variation, but through the acc.u.mulation of psychical variations one particular species was to be indefinitely perfected and raised to a totally different plane from that on which all life had hitherto existed. Henceforth, in short, the dominant aspect of evolution was to be not the genesis of species, but the progress of Civilization.

As we thoroughly grasp the meaning of all this, we see that upon the Darwinian theory it is impossible that any creature zoologically distinct from Man and superior to him should ever at any future time exist upon the earth. In the regions of unconditional possibility it is open to any one to argue, if he chooses, that such a creature may come to exist; but the Darwinian theory is utterly opposed to any such conclusion. According to Darwinism, the creation of Man is still the goal toward which Nature tended from the beginning. Not the production of any higher creature, but the perfecting of Humanity, is to be the glorious consummation of Nature"s long and tedious work. Thus we suddenly arrive at the conclusion that Man seems now, much more clearly than ever, the chief among G.o.d"s creatures. On the primitive barbaric theory, which Mr. Darwin has swept away, Man was suddenly flung into the world by the miraculous act of some unseen and incalculable Power acting from without; and whatever theology might suppose, no scientific reason could be alleged why the same incalculable Power might not at some future moment, by a similar miracle, thrust upon the scene some mightier creature in whose presence Man would become like a sorry beast of burden. But he who has mastered the Darwinian theory, he who recognizes the slow and subtle process of evolution as the way in which G.o.d makes things come to pa.s.s, must take afar higher view. He sees that in the deadly struggle for existence which has raged throughout countless aeons of time, the whole creation has been groaning and travailing together in order to bring forth that last consummate specimen of G.o.d"s handiwork, the Human Soul.

To the creature thus produced through a change in the direction in which natural selection has worked, the earth and most of its living things have become gradually subordinated. In all the cla.s.ses of the animal and vegetal worlds many ancient species have become extinct, and many modern species have come into being, through the unchecked working of natural selection, since Man became distinctively human. But in this respect a change has long been coming over the face of nature. The destinies of all other living things are more and more dependent upon the will of Man. It rests with him to determine, to a great degree, what plants and animals shall remain upon the earth and what shall be swept from its surface. By unconsciously imitating the selective processes of Nature, he long ago wrought many wild species into forms subservient to his needs. He has created new varieties of fruit and flower and cereal gra.s.s, and has reared new breeds of animals to aid him in the work of civilization; until at length he is beginning to acquire a mastery over mechanical and molecular and chemical forces which is doubtless destined in the future to achieve marvellous results whereof today we little dream. Natural selection itself will by and by occupy a subordinate place in comparison with selection by Man, whose appearance on the earth is thus seen more clearly than ever to have opened an entirely new chapter in the mysterious history of creation.

IV.

The Origin of Infancy.

But before we can fully understand the exalted position which the Darwinian theory a.s.signs to man, another point demands consideration.

The natural selection of psychical peculiarities does not alone account for the origin of Man, or explain his most signal difference from all other animals. That difference is unquestionably a difference in kind, but in saying this one must guard against misunderstanding. Not only in the world of organic life, but throughout the known universe, the doctrine of evolution regards differences in kind as due to the gradual acc.u.mulation of differences in degree. To cite a very simple case, what differences of kind can be more striking than the differences between a nebula, a sun, a planet like the earth, and a planet like our moon? Yet these things are simply examples of cosmical matter at four different stages of cooling. The physical differences between steam, water, and ice afford a more familiar example. In the organic world the perpetual modification of structures that has been effected through natural selection exhibits countless instances of differences in kind which have risen from the acc.u.mulation of differences in degree. No one would hesitate to call a horse"s hoof different in kind from a cat"s paw; and yet the horse"s lower leg and hoof are undoubtedly developed from a five-toed paw. The most signal differences in kind are wont to arise when organs originally developed for a certain purpose come to be applied to a very different purpose, as that change of the fish"s air-bladder into a lung which accompanied the first development of land vertebrates. But still greater becomes the revolution when a certain process goes on Until it sets going a number of other processes, unlocking series after series of causal agencies until a vast and complicated result is reached, such as could by no possibility have been foreseen. The creation of Man was one of these vast and complicated results due to the unlocking of various series of causal agencies; and it was the beginning of a deeper and mightier difference in kind than any that slowly evolving Nature had yet witnessed.

I have indicated, as the moment at which the creation of mankind began, the moment when psychical variations became of so much more use to our ancestors than physical variations that they were seized and enhanced by natural selection, to the comparative neglect of the latter. Increase of intellectual capacity, in connection with the developing brain of a single race of creatures, now became the chief work of natural selection in originating Man; and this, I say, was the opening of a new chapter, the last and most wonderful chapter, in the history of creation. But the increasing intelligence and enlarged experience of half-human man now set in motion a new series of changes which greatly complicated the matter. In order to understand these changes, we must consider for a moment one very important characteristic of developing intelligence.

The simplest actions in which the nervous system is concerned are what we call reflex actions. All the visceral actions which keep us alive from moment to moment, the movements of the heart and lungs, the contractions of arteries, the secretions of glands, the digestive operations of the stomach and liver, belong to the cla.s.s of reflex actions. Throughout the animal world these acts are repeated, with little or no variation, from birth until death, and the tendency to perform them is completely organized in the nervous system before birth.

Every animal breathes and digests as well at the beginning of his life as he ever does. Contact with air and food is all that is needed, and there is nothing to be learned. These actions, though they are performed by the nervous system, we do not cla.s.s as psychical, because they are nearly or quite unattended by consciousness. The psychical life of the lowest animals consists of a few simple acts directed toward the securing of food and the avoidance of danger, and these acts we are in the habit of cla.s.sing as instinctive. They are so simple, so few, and so often repeated, that the tendency to perform them is completely organized in the nervous system before birth. The animal takes care of himself as soon as he begins to live. He has nothing to learn, and his career is a simple repet.i.tion of the careers of countless ancestors.

With him heredity is everything, and his individual experience is next to nothing.

As we ascend the animal scale till we come to the higher birds and mammals, we find a very interesting and remarkable change beginning. The general increase of intelligence involves an increasing variety and complication of experiences. The acts which the animal performs in the course of its life become far more numerous, far more various, and far more complex. They are therefore severally repeated with less frequency in the lifetime of each individual. Consequently the tendency to perform them is not completely organized in the nervous system of the offspring before birth. The short period of ante-natal existence does not afford time enough for the organization of so many and such complex habitudes and capacities. The process which in the lower animals is completed before birth is in the higher animals left to be completed after birth.

When the creature begins its life it is not completely organized.

Instead of the power of doing all the things which its parents did, it starts with the power of doing only some few of them; for the rest it has only latent capacities which need to be brought out by its individual experience after birth. In other words, it begins its separate life not as a matured creature, but as an infant which needs for a time to be watched and helped.

V.

The Dawning of Consciousness.

Here we arrive at one of the most wonderful moments in the history of creation,--the moment of the first faint dawning of consciousness, the foreshadowing of the true life of the soul. Whence came the soul we no more know than we know whence came the universe. The primal origin of consciousness is hidden in the depths of the bygone eternity. That it cannot possibly be the product of any cunning arrangement of material particles is demonstrated beyond peradventure by what we now know of the correlation of physical forces.[4] The Platonic view of the soul, as a spiritual substance, an effluence from G.o.dhood, which under certain conditions becomes incarnated in perishable forms of matter, is doubtless the view most consonant with the present state of our knowledge. Yet while we know not the primal origin of the soul, we have learned something with regard to the conditions under which it has become incarnated in material forms. Modern psychology has something to say about the dawning of conscious life in the animal world. Reflex action is unaccompanied by consciousness. The nervous actions which regulate the movements of the viscera go on without our knowledge; we learn of their existence only by study, as we learn of facts in outward nature. If you tickle the foot of a person asleep, and the foot is withdrawn by simple reflex action, the sleeper is unconscious alike of the irritation and of the movement, even as the decapitated frog is unconscious when a drop of nitric acid falls on his back and he lifts up a leg and rubs the place. In like manner the reflex movements which make up the life of the lowest animals are doubtless quite unconscious, even when in their general character they simulate conscious actions, as they often do. In the case of such creatures, the famous hypothesis of Descartes, that animals are automata, is doubtless mainly correct. In the case of instincts also, where the instinctive actions are completely organized before birth, and are repeated without variation during the whole lifetime of the individual, there is probably little if any consciousness. It is an essential prerequisite of consciousness that there should be a period of delay or tension between the receipt of an impression and the determination of the consequent movement. Diminish this period of delay and you diminish the vividness of consciousness. A familiar example will make this clear. When you are learning to play a new piece of music on the piano, especially if you do not read music rapidly, you are intensely conscious of each group of notes on the page, and of each group of keys that you strike, and of the relations of the one to the other. But when you have learned the piece by heart, you think nothing of either notes or keys, but play automatically while your attention is concentrated upon the artistic character of the music. If somebody thoughtlessly interrupts you with a question about Egyptian politics, you go on playing while you answer him politely. That is, where you had at first to make a conscious act of volition for each movement, the whole group of movements has now become automatic, and volition is only concerned in setting the process going. As the delay involved in the perception and the movement disappears, so does the consciousness of the perception and the movement tend to disappear.

Consciousness implies perpetual discrimination, or the recognition of likenesses and differences, and this is impossible unless impressions persist long enough to be compared with one another. The physical organs in connection with whose activity consciousness is manifested are the upper and outer parts of the brain,--the cerebrum and cerebellum. These organs never receive impressions directly from the outside world, but only from lower nerve-centres, such as the spinal cord, the medulla, the optic lobes, and other special centres of sensation. The impressions received by the cerebrum and cerebellum are waves of molecular disturbance sent up along centripetal nerves from the lower centres, and presently drafted off along centrifugal nerves back to the lower centres, thus causing the myriad movements which make up our active life. Now there is no consciousness except when molecular disturbance is generated in the cerebrum and cerebellum faster than it can be drafted off to the lower centres.[5] It is the surplus of molecular disturbance remaining in the cerebrum and cerebellum, and reflected back and forth among the cells and fibres of which these highest centres are composed, that affords the physical condition for the manifestation of consciousness. Memory, emotion, reason, and volition begin with this retention of a surplus of molecular motion in the highest centres. As we survey the vertebrate sub-kingdom of animals, we find that as this surplus increases, the surface of the highest centres increases in area.

In the lowest vertebrate animal, the amphioxus, the cerebrum and cerebellum do not exist at all. In fishes we begin to find them, but they are much smaller than the optic lobes. In such a highly organized fish as the halibut, which weighs about as much as an average-sized man, the cerebrum is smaller than a melon-seed. Continuing to grow by adding concentric layers at the surface, the cerebrum and cerebellum become much larger in birds and lower mammals, gradually covering up the optic lobes. As we pa.s.s to higher mammalian forms, the growth of the cerebrum becomes most conspicuous, until it extends backwards so far as to cover up the cerebellum, whose functions are limited to the conscious adjustment of muscular movements. In the higher apes the cerebrum begins to extend itself forwards, and this goes on in the human race. The cranial capacity of the European exceeds that of the Australian by forty cubic inches, or nearly four times as much as that by which the Australian exceeds the gorilla; and the expansion is almost entirely in the upper and anterior portions. But the increase of the cerebral surface is shown not only in the general size of the organ, but to a still greater extent in the irregular creasing and furrowing of the surface. This creasing and furrowing begins to occur in the higher mammals, and in civilized man it is carried to an astonishing extent.

The amount of intelligence is correlated with the number, the depth, and the irregularity of the furrows. A cat"s brain has a few symmetrical creases. In an ape the creases are deepened into slight furrows, and they run irregularly, somewhat like the lines in the palm of your hand.

With age and experience the furrows grow deeper and more sinuous, and new ones appear; and in man these phenomena come to have great significance. The cerebral surface of a human infant is like that of an ape. In an adult savage, or in a European peasant, the furrowing is somewhat marked and complicated. In the brain of a great scholar, the furrows are very deep and crooked, and hundreds of creases appear which are not found at all in the brains of ordinary men. In other words, the cerebral surface of such a man, the seat of conscious mental life, has become enormously enlarged in area; and we must further observe that it goes on enlarging in some cases into extreme old age.[6]

Putting all these facts together, it becomes plain that in the lowest animals, whose lives consist of sundry reflex actions monotonously repeated from generation to generation, there can be nothing, or next to nothing, of what we know as consciousness. It is only when the life becomes more complicated and various, so that reflex action can no longer determine all its movements and the higher nerve-centres begin to be evolved, that the dawning of consciousness is reached. But with the growth of the higher centres the capacities of action become so various and indeterminate that definite direction is not given to them until after birth. The creature begins life as an infant, with its partially developed cerebrum representing capabilities which it is left for its individual experience to bring forth and modify.