Popular Science Monthly/Volume 39/September 1891/The Doctrine of Evolution: Its Scope and Influence
|THE DOCTRINE OF EVOLUTION: ITS SCOPE AND INFLUENCE.|
IF you take up almost any manual or compendium of history written before the middle of the present century, you will generally find it to be a lifeless catalogue of events, and more likely than not an undiscriminating catalogue in which important and trivial events are jumbled together in utter obliviousness of any such thing as historical perspective. Of great and admirable books of history there were indeed many by illustrious writers of ancient and modern times, in which the men, the measures, and the social features of particular epochs were portrayed with life-like reality and often illustrated and criticised with a wealth of practical wisdom. But the insight into the underlying causes and the general drift of the endlessly complicated mass of human affairs was dim and uncertain, and of the essential unity of history, the solidarity in the multifarious career of mankind, there was hardly a suspicion. Three great books in narrative form, which reached out toward a presentation of the unity of history, may be cited in illustration of the difficulty under which all such attempts necessarily labored in the absence of such broad scientific conceptions as have been gained only within recent times. Bossuet's Discourse on Universal History was a work of noble design; but, being necessarily limited by the narrow theology of the time, it could only see the vast importance of the work of the Hebrew race, and, seeing no further, could not properly estimate even this; while as for any appreciation of natural causes, its perpetual appeal to the miraculous made anything of the sort quite impossible. In Voltaire's Essay on the Manners and Morals of Nations there is a strong foreshadowing of the unity of history, but very slight practical recognition of the differences between one stage of civilization and another, and the philosophy of the book is quite too much that of a sermon on the evils of priestcraft. In the colossal work of Gibbon there is a dramatic unity of design and a sense of historical perspective that from an artistic point of view can not be praised too highly. It is, no doubt, an immortal book, one of the classics for all ages; but as an interpretation of events it goes but little way. The period of twelve hundred years which it covers was crowded with facts of decisive import for all future time which failed to arrest the author's attention. There is no consciousness that this period, which witnessed the decline and overthrow of a certain phase of political organization, was in the main a period of lusty growth and wholesome progress rather than a period of stagnation or decline. Nor, indeed, is there any explanation of the great conspicuous fact of the decline and fall of the Roman imperial organization; we are told what events happened, and often how they happened, but we are seldom made to understand why they happened. The grasp upon the underlying causes is extremely feeble, as one can not but feel in a moment if, after laying down Gibbon, one picks up a volume of Mommsen, or Freeman, or Sir Henry Maine.
Most of the shortcomings of the old method of historical writing resulted from the fact that the world was looked at from a statical point of view, or as if a picture of the world were a series of detached pictures of things at rest. The human race and its terrestrial habitat were tacitly assumed to have been always very much the same as at present. One age was treated much like another, and when comparisons were made it was after a manner as different from the modern comparative method as alchemy was different from chemistry. As men's studies had not yet been turned in such a direction as to enable them to appreciate the immensity of the results that are wrought by the cumulative action of minute causes, they were disposed to attach too much importance to the catastrophic and marvelous; and the agency of powerful individuals—which upon any sound theory must be' regarded as of great importance—they not only magnified unduly but rendered it unintelligible when they sought to transform human heroes into demi-gods.
It thus appears that the way in which our forefathers treated history was part and parcel of the way in which they regarded the world. Whether in history or in the physical sciences, they found themselves confronted by a seemingly chaotic mass of facts with which they could deal only in a vague and groping manner and in small detached groups. Until geology had made some headway, men had no means of knowing that the state of things upon the earth's surface,was once utterly different from anything that human tradition can remember, and it was accordingly quite natural that they should suppose that things have always been about as they are. The human mind can not transcend experience. The man who has always lived in a comparatively unchanged environment will, of course, never believe in a different state of things until taught by some fresh experience. How long it was before it was brought home to men that the testimony of the unaided senses needs to be corrected by systematic observation and reasoning! From this point of view, as indeed from some others also, the revolution in astronomical theory effected by Copernicus was one of the greatest events in human history. Its philosophic consequences were profound. In teaching men the necessity of going back of superficial appearances, and subjecting their crude opinions to some kind of critical test, it was an object lesson of unsurpassed value. Along with this abrupt shifting of man's apparent position in the universe, came the astonishing results of oceanic discovery, enlarging fourfold the dimensions of the known world and bringing the mind into contact with organic and inorganic nature in various new and unsuspected forms. Then came the Newtonian astronomy, in which a generalization from terrestrial physics was extended into the celestial spaces and quantitatively verified. There was an immense enlargement of the mental horizon, and the problems immediately connected with it were enough to occupy the attention of all the foremost mathematical minds for more than a century. It made man a denizen of the solar system as well as of his own particular planet; and in these latter days, since the law of gravitation has been extended to the sidereal heavens and spectrum analysis has begun to deal with nebula?, there is abundant proof that properties of matter and processes with which we are familiar on this earth are to be found in some of the remotest bodies which the telescope can reach, and it is thus forcibly impressed upon us that all are parts of one stupendous whole.
This enlargement of the mental horizon, from Newton to Kirchhoff, had reference to space. A similar enlargement with reference to time was an indispensable preliminary to any correct understanding of how the world is made and what is going on in it. But, before much headway could be made in geology, it was necessary that physics and chemistry, the sciences which generalize the properties of matter, in the mass and in the molecule, should be to some extent apprehended; and it is almost startling to think how modern all this is—scarcely more than a hundred years since Priestley discovered oxygen, since it became possible to tell what goes on when you burn a log of wood on the hearth! and not so very much longer since Black discovered latent heat and gave us a clew to what happens when water freezes and.melts or when it is turned into steam! It is only within fifty years that physics and chemistry have begun to assume the form of coherent bodies of scientific truth. Evidently geology could not be expected to take scientific shape until late in the eighteenth century, or to make any notable conquests before the nineteenth. But when geology did win its first great triumph, about sixty years ago, it was in some ways the most remarkable moment in the history of thought since the promulgation of the Newtonian astronomy. Newton proved that the forces which keep the planets in their orbits are not strange or supernatural forces, but just such forces as we are familiar with on this earth every moment of our lives. Geologists before Lyell had been led to the conclusion that the general aspect of the earth's surface with which we are familiar is by no means its primitive or its permanent aspect, but that there has been a succession of ages in which the relations of land and water, of mountain and plain have varied to a very considerable extent, in which soils and climates have undergone most complicated vicissitudes, and in which the earth's vegetable products and its animal populations have again and again assumed new forms while the old forms have passed away. In order to account for such wholesale changes, geologists were at first disposed to imagine violent catastrophes brought about by strange agencies—agencies which were perhaps not exactly supernatural, but in some unspecified way different from the agencies that are now at work in the visible and familiar order of Nature. But Lyell proved that the very same kind of physical processes which are now going on about us would suffice during a long period of time to produce the changes in the inorganic world which distinguish one geological period from another. Here, in Lyell's geological investigations, there was for the first time due attention paid to the immense importance of the prolonged and cumulative action of slight and unobtrusive causes. The continual dropping that wears away stones might have served as a text for the whole series of beautiful researches of which he first summed up the results in 1830. As astronomy was steadily advancing toward the proof that in the remotest abysses of space the physical forces at work are the same as terrestrial forces; so now geology, in carrying us back to enormously remote periods of time, began to teach that the forces at work have all along been the same forces that are at work now. In that early stage when the earth's crust was in process of formation, when the temperature was excessively high, there were, of course, phenomena such as can not now be witnessed here, but to find a parallel to which we must look to certain other planets—such as violent atmospheric disturbances, and such as the dissociation of chemical elements which we are accustomed to find in close combination. But since the cooling of the earth to a point at which its solid crust acquired stability, since the ancestors of the amphioxus began to swim in the seas and worms to crawl in the ground, if you could at almost any time have visited the earth, you would doubtless have found things going on at measured pace very much as at present—here and there earthquake and avalanche, fire and flood, but generally rain falling, sunshine quickening, herbage sprouting, creatures browsing, all as quiet and peaceful as a daisied field in June, without the slightest presage of the continuous series of secular changes that were gradually to transform the Carboniferous world into what was by and by to be a Jurassic world, and that again into what was after a while to be an Eocene world, and so on until the aspect of the world which we know should quietly emerge.
The influence of the new geology upon men's habits of thought and upon the drift of philosophic speculation was profound. It was proved beyond question that the world was not created in the form in which we find it to-day, but has gone through many phases of which the later are very different in aspect from the earlier; and it was shown that, at any rate so far as the inorganic world is concerned, its changes can be much more satisfactorily explained by a reference to the ceaseless, all-pervading activity of gentle, unobtrusive causes such as we know, than by an appeal to imaginary catastrophes such as we have no means of verifying. It began to appear, also, that the facts which form the subject matter of different departments of science are not detached and independent groups of facts, but that all are intimately related one with another, and that all may be brought under contribution in illustrating the history of cosmical events. Thus, in one way and another, about the time when Mr. Darwin set out on his memorable voyage around the world, men were beginning to arrive at a vague general conception of evolution as an orderly succession of phases of nature, in which any given phase is produced from an antecedent phase through the agency of causes which are like those now in operation, and which must therefore admit of definite scientific study and explanation.
The time had at length arrived when the facts of organic life could be brought under this general conception. As long as it was supposed that each geologic period was separated from the periods immediately before and after it by Titanic convulsions which revolutionized the face of the globe, it was possible for men to acquiesce in the supposition that these convulsions wrought an abrupt and wholesale destruction of organic life, and that the lost forms were replaced by an equally abrupt and wholesale supernatural creation of new forms at the beginning of each new period. But as people ceased to believe in the convulsions, such an explanation began to seem very improbable, and it was completely discredited by the fact that many kinds of plants and animals have persisted with little or no change during several successive periods, side by side with other kinds in which there has been extensive variation and extinction. It was further observed that between the forms of successive periods in the same geographical regions there was a manifest family likeness, indicating that the later were connected with the earlier through the ordinary bonds of physical descent. A host of facts from comparative morphology and embryology went to confirm this inference; and so, when after nearly twenty years of incubation Mr. Darwin was ready to plant the seeds of his remarkable theory, he found the soil very thoroughly prepared and fertilized in which to plant them. All that men were waiting for was the discovery of a vera causa, All that was wanted was to be able to point to some one agency, similar to agencies now in operation and therefore intelligible, which could be proved to be capable of making specific changes in plants and animals. Mr. Darwin's solution of the problem was so beautiful, it has become so generally accepted and so deeply interfused into all the thinking of our time, it seems now so natural and so inevitable, that we may be in danger of forgetting that the problem was really one of the most complicated and abstruse that the scientific mind has ever grappled with. Starting from the known experiences of breeders of domestic animals and cultivated plants, and duly considering the remarkable and sometimes wonderful changes that are wrought by the simple process of selection, the problem before Mr. Darwin was to detect among the multifarious phenomena of organic nature any agency capable of accomplishing what man thus accomplishes by selection. In detecting the agency of natural selection, working perpetually through the preservation of favored individuals and races in the struggle for existence, Mr. Darwin found the vera causa for which men were waiting. With infinite patience and caution he applied his method of explanation to one group of organic phenomena after another, meeting in every quarter with fresh and often unexpected verification. He had the satisfaction of living to see pretty much the whole contemporary world of zoölogists, botanists, and palæontologists pursuing the lines of investigation which he had laid down and in general agreement as to the fundamental principle. There was a general acquiescence in natural selection as an agency capable of working specific changes, while further speculation and investigation in all directions were employed in ascertaining the precise character of its work and determining the limits of its efficacy. That all the phenomena of the organic world can be accounted for by natural selection, Mr. Darwin never at any time supposed; nor was he ever so silly as to suppose that all difficulties had been removed by himself or were likely to be removed within a single generation by the collective work of the whole scientific world. The present generation has witnessed a tendency toward restricting the probable limits of the efficacy of natural selection, followed by an equally marked tendency toward enlarging them—a tendency likely to be furthered by Mr. Wallace's recent book, pointing out the great extent of variation that normally goes on within the limits of one and the same species. Such minor fluctuations in scientific theory occur in all departments of inquiry, but no one doubts the essential soundness of the Darwinian theory, and as for the doctrine of special creations which it superseded, we shall probably go back to it when we go back to stone arrow-heads and the primitive Aryan ox-cart, and not before.
It has more than once been observed that, when a new discovery in science is announced to the world, people at first scout it as ridiculous or frown upon it as impious, but afterward, when it is no longer possible to gainsay it, they suddenly find that everybody knew all about it long ago. This habit is probably due to an exaggerated regard for consistency and a failure to realize that the thoughts of men are, and ought to be, widened with the progress of the suns. About the origin and history of the doctrine of evolution there is in the popular mind a great confusion of ideas; and this, as we now begin to see, is because the conception of evolution is itself something which has grown up gradually. It is an end toward which the whole momentum of scientific thought since Newton's day has been tending, yet which has been clearly and fully recognized only of late years. As regards Mr. Darwin's contribution to the general result, it admits of precise definition. The doctrine of natural selection, which Mr. Spencer afterward called " the survival of the fittest," belongs to Mr. Darwin and to Mr. Wallace as much as the differential calculus belongs to Newton and Leibnitz. The same problem was solved in the same way, first by Mr. Darwin, and then a dozen years later by Mr. Wallace in complete ignorance of what Mr. Darwin had done. " Darwinism" is the doctrine which maintains that many different forms of animal and vegetable life have a common ancestry, and which defines and describes natural selection as the chief agent in bringing about divergencies. Its distinctive feature—that which constitutes its value and its grandeur as a scientific doctrine—is the discovery and demonstration of the agency of natural selection. No one anticipated Mr. Darwin in that.
But the doctrine of natural selection is one thing, and the doctrine of evolution is quite another thing. It covers much more ground, and a good deal of it is ground with which Mr. Darwin had little or nothing to do. Vague notions of evolution were in the air long before Darwin. When Emerson speaks of the worm mounting through the various spheres of form, we are sometimes told that in this and other similar remarks he anticipated Darwin. But such language is misleading. Great writers might have gone on until the present moment expressing a conviction that higher forms of life have been evolved from lower forms, but all that would have been of small avail as scientific doctrine until somebody could show how it has been done. The belief in an evolution of higher from lower organisms was held by a few eminent men of science for a great part of the century preceding Mr. Darwin's discovery. It is a belief that could not fail to be strongly suggested to minds of a certain philosophic cast as soon as the classification of plants and animals had begun to be conducted upon scientific principles. It is not for nothing that a table of classes, orders, families, genera, and species, when graphically laid out, resembles a family tree. It was not long after Linnaeus that believers in some sort of a development theory, often fantastic enough, began to appear. Palæontology gave further suggestions in the same direction. When Cuvier brought palæontology into alliance with systematic zoölogy, and effected his grand classification of animals in space and time, he prepared the way most thoroughly for a theory of evolution, though he always resisted any such inference from his work. He builded better than he knew. A general belief in development, as opposed to special creations, was held by Mr. Darwin's distinguished grandfather in England, by Lamarck and Geoffroy Saint-Hilaire in France, and by Oken and Goethe in Germany. In the present age it was maintained in print by Herbert Spencer in 1852, before Darwin had published anything on the subject.
During the early part of the present century applications of the comparative method in various directions were rapidly educating the minds of the younger generation of students into a vague perception of development as something characteristic of all sorts of phenomena. The first two great triumphs of the comparative method were achieved contemporaneously in two fields of inquiry very remote from one another: the one was the work of Cuvier just mentioned, the other was the founding of the comparative philology of the Aryan languages by Franz Bopp in 1816. The work of Bopp exerted as powerful an influence throughout all the historical fields of study as Cuvier exerted in biology. The young men whose minds were receiving their formative impulses between 1825 and 1840, under the various influences of Cuvier and Saint-Hilaire, Lyell, Goethe, Bopp, and other such great leaders, began themselves to come to the foreground as leaders of thought about 1800, on the one hand, such men as Darwin, Gray, Huxley, and Wallace; on the other hand, such as Kuhn and Schleicher, Maine, Maurer, Mommsen, Freeman, and Tylor. The point of the comparative method, in whatever field it may be applied, is that it brings before us a great number of objects so nearly alike that we are bound to assume for them an origin and general history in common, while at the same time they present such differences in detail as to suggest that some have advanced further than others in the direction in which all are traveling; some, again, have been abruptly arrested, others perhaps even turned aside from the path. In the attempt to classify such phenomena, whether in the historical or in the physical sciences, the conception of development is presented to the student with irresistible force. In the case of the Aryan languages no one would think of doubting their descent from a common original; just side by side is the parallel case of one subgroup of the Aryan languages, namely, the seven Romance languages which we know to have been developed out of the Latin since the Christian era. In these cases we can study the process of change resulting in forms that are more or less divergent from their originals. In one quarter a form is retained with little modification, in another it is completely blurred, as the Latin metipsissimus becomes medesimo in Italian, but mismo in Spanish, while in French there is nothing left of it but même. So in Sanskrit and in Lithuanian we find a most ingenious and elaborate system of conjugation and declension, which in such languages as Greek and Latin is more or less curtailed and altered, and which in English is almost completely lost. Yet in Old English there are quite enough vestiges of the system to enable us to identify it with the Lithuanian and Sanskrit.
So the student who applies the comparative method to the study of human customs and institutions is continually finding usages, beliefs, or laws existing in one part of the world that have long since ceased to exist in another part; yet where they have ceased to exist they have often left unmistakable traces of their former existence. In Australasia we find types of savagery ignorant of the bow and arrow; in aboriginal North America, a type of barbarism familiar with the art of pottery, but ignorant of domestic animals or of the use of metals; among the earliest Romans, a higher type of barbarism, familiar with iron and cattle, but ignorant of the alphabet. Along with such gradations in material culture we find associated gradations in ideas, in social structure, and in deep-seated customs. Thus, some kind of fetichism is apt to prevail in the lower stages of barbarism, and some form of polytheism in the higher stages. The units of composition in savage and barbarous societies are always the clan, the phratry, and the tribe. In the lower stages of barbarism we see such confederacies as those of the Iroquois; in the highest stage, at the dawn of civilization, we begin to find nations imperfectly formed by conquest without incorporation, like aboriginal Peru or ancient Assyria. In the lower stages we see captives tortured to death, then at a later stage sacrificed to the tutelar deities, then later on enslaved and compelled to till the soil. Through all the earlier stages of culture, as in Australasia and aboriginal America, we find the marriage tie so loose and paternity so uncertain that kinship is reckoned only through the mother. But in the highest stage of barbarism, as among the earliest Greeks, Romans, and Jews, the more definite patriarchal family is developed and kinship begins to be reckoned through the father. It is only after that stage is reached that inheritance of property becomes fully developed, with the substitution of individual ownership for clan ownership, and so on to the development of testamentary succession, individual responsibility for delict and crime, and the substitution of contract for status. In all such instances, and countless others might be cited, we see the marks of an intelligible progression, a line of development which human ideas and institutions have followed. But in the most advanced societies we find numerous traces of such states of things as now exist only among savage or barbarous societies. Our own ancestors were once polytheists, with plenty of traces of fetichism. They were organized in clans, phratries, and tribes. There was a time when they used none but stone tools and weapons, when there was no private property in land, and no political structure higher than the tribe. Among the forefathers of the present civilized inhabitants of Europe are unmistakable traces of human sacrifices and of the reckoning of kinship through the mother only. When we have come to survey large groups of facts of this sort, the conclusion is irresistibly driven home to us that the more advanced societies have gone through various stages now represented here and there by less advanced societies; that there is a general path of social development, along which, owing to special circumstances, some peoples have advanced a great way, some a less way, some but a very little way; and that, by studying existing savages and barbarians, we get a valuable clew to the interpretation of prehistoric times. All these things are to-day commonplaces among students of history and archæology: sixty years ago they would have been scouted as unintelligible and idle vagaries. Yet to this change is entirely due the superior power of modern historical methods. Formerly the historian told anecdotes or discussed particular lines of policy; now he can do that as much as ever, but he can also study nation-building and discern some features of the general drift of events from the earliest to the most recent times.
If we leave the earth and its inhabitants and turn our attention to the starry heavens, we find plenty of subjects for comparison indicating that there is a general process going on, and that this process has advanced much further in some places than in others. The general process may be roughly described as concentration of cosmical matter, with dissipation of heat. Along with this go sundry attendant or derivative chemical changes. We find gaseous nebulae; stars ranked in different classes by their colors, perhaps indicating different stages of progress toward consolidation; then planets, first huge ones, like Saturn and Jupiter, with small density, tremendous atmospherical disturbances, and probably some remains of self-luminosity; then such as Mars, Earth, and Venus, with cool, vapor-laden atmospheres and conditions favorable to organic life; then smaller, quickly cooled and solidified globes like our barren moon; then cosmic rubbish like the asteroids and cosmic dust like the meteors. All, of course, are losing heat. Some have cooled too quickly to allow the development of life upon their surfaces; others are still too hot, but while in this stage can perhaps supply radiant heat and actinism for the support of life upon their neighbors. Obviously the gaseous nebula, being a body in an earlier stage of consolidation and containing a maximum of internal motion, is to be regarded as something like what suns and their planets were in a former stage of development.
Long before all these fruits of modern astronomical observation had been gathered, the contemplation of our sun as a consolidating and radiating body had suggested to one of the most profound thinkers that ever lived the famous nebular hypothesis as an account of the mode of development of our planetary system. The nebular hypothesis, set forth by Immanuel Kant in 1755, was the first constructive work toward a definite doctrine of evolution. The theory was restated in 1796 by Laplace, whose line of argument was very similar to Kant's. "Within recent years it has received emendations and qualifications, but the fundamental conception of the nebulous mass acquiring spheroidal shape through rotation, and increasing in oblateness until at some stage in its shrinkage a portion of the equatorial surface is detached as a ring of fragments which ultimately coalesce into a satellite globe—this fundamental conception still remains as a good working hypothesis.
As we now look back over the illustrations here cited—and they are, of course, scanty enough in comparison with what might be adduced—it appears that about half a century ago the foremost minds of the world, with whatever group of phenomena they were occupied, had fallen and were more and more falling into a habit of regarding things not as having originated in the shape in which we now find them, but as having been slowly metamorphosed from some other shape through the agency of forces similar in nature to forces now at work. Whether planets, or mountains, or mollusks, or subjunctive moods, or tribal confederacies were the things studied, the scholars who studied them most deeply and most fruitfully were those who studied them as phases in a process of development. The work of such scholars has formed the strong current of thought in our time, while the work of those who did not catch these new methods has been dropped by the way and forgotten. And as we look back to Newton's time we can see that ever since then the drift of scientific thought has been setting in this direction, and with increasing steadiness and force.
Now, what does all this drift of scientific opinion during more than two centuries mean? It can, of course, have but one meaning. It means that the world is in a process of development, and that gradually, as advancing knowledge has enabled us to take a sufficiently wide view of the world, we have come to see that it is so. The old statical conception of a world created all at once in its present shape was the result of very narrow experience; it was entertained when we knew only an extremely small segment of the world. Now that our experience has widened, it is outgrown and set aside forever; it is replaced by the dynamical conception of a world in a perpetual process of evolution from one state into another state. This dynamical conception has come to stay with us. Our theories as to what the process of evolution is may be more or less wrong and are confessedly tentative, as scientific theories should be. But the dynamical conception, which is not the work of any one man, be he Darwin or Spencer or any one else, but the result of the cumulative experience of the last two centuries, this is a permanent acquisition. We can no more revert to the statical conception than we can turn back the sun in his course. Whatever else the philosophy of future generations may be, it must be a philosophy of evolution.
It was not strange that among the younger men whose opinions were molded between 1830 and 1840 there should have been one of organizing genius, with a mind inexhaustibly fertile in suggestions, who should undertake to elaborate a general doctrine of evolution, to embrace in one grand coherent system of generalizations all the minor generalizations which workers in different departments of science were establishing. It is this prodigious work of construction that we owe to Herbert Spencer. He is the originator and author of what we know to-day as the doctrine of evolution, the doctrine which undertakes to formulate and put into scientific shape the conception of evolution toward which scientific investigation had so long been tending. In the mind of the general public there seems to be dire confusion with regard to Mr. Spencer and his relations to evolution and to Darwinism. Sometimes, I believe, he is even supposed to be chiefly a follower and expounder of Mr. Darwin! No doubt this is because so many people mix up Darwinism with the doctrine of evolution, and have but the vaguest and haziest notions as to what it is all about. As I explained above, Mr. Darwin's great work was the discovery of natural selection and the demonstration of its agency in effecting specific changes in plants and animals; and in that work he was completely original. But plants and animals are only a part of the universe, though an important part, and with regard to universal evolution or any universal formula for evolution Darwinism had nothing to say. Such problems were beyond its scope.
The discovery of a universal formula for evolution, and the application of this formula to many diverse groups of phenomena, have been the great work of Mr. Spencer, and in this he has had no predecessor. His wealth of originality is immense, and it is unquestionable. But as the most original thinker must take his start from the general stock of ideas accumulated at his epoch, and more often than not begins by following a clew given him by somebody else, so it was with Mr. Spencer when about forty years ago he was working out his doctrine of evolution. The clew was not given him by Mr. Darwin. Darwinism was not yet born. Mr. Spencer's theory was worked out in all its parts, and most parts of it had been expounded in various published volumes and essays before the publication of The Origin of Species.
The clew which Mr. Spencer followed was given him by the great German embryologist Von Baer, and an adumbration of it may perhaps be traced back through Kaspar Friedrich Wolf to Linnæus. Hints of it may be found, too, in Goethe and in Schelling. The advance from simplicity to complexity in the development of an egg is too obvious to be overlooked by any one, and was remarked upon, I believe, by Harvey; but the analysis of what that advance consists in was a wonderfully suggestive piece of work. Von Baer's great book was published in 1829, just at the time when so many stimulating ideas were being enunciated, and its significant title was Entwickelungsgeschiclite, or History of Evolution. It was well known that, so far as the senses can tell us, one ovum is indistinguishable from another, whether it be that of a man, a fish, or a parrot. The ovum is a structureless bit of organic matter, and in acquiring structure along with its growth in volume and mass, it proceeds through a series of differentiations, and the result is a change from homogeneity to heterogeneity. Such was Von Baer's conclusion, to which scanty justice is done by such a brief statement. As all know, his work marked an epoch in the study of embryology, for to observe and mark the successive differentiations in the embryos of a thousand animals were to write a thousand life-histories upon correct principles.
Here it was that Mr. Spencer started. As a young man he was chiefly interested in the study of political government and in history so far as it helps the study of politics. A philosophical student of such subjects must naturally seek for a theory of evolution. If I may cite my own experience, it was largely the absorbing and overmastering passion for the study of history that first led me to study evolution in order to obtain a correct method. When one has frequent occasion to refer to the political and social progress of the human race, one likes to know what one is talking about. Mr. Spencer needed a theory of progress. He could see that the civilized part of mankind has undergone some change from a bestial, unsocial, perpetually fighting stage of savagery into a partially peaceful and comparatively humane and social stage, and that we may reasonably hope that the change in this direction will go on. He could see, too, that along with this change there has been a building up of tribes into nations, a division of labor, a differentiation of governmental functions, a series of changes in the relations of the individual to the community. To see so much as this is to whet one's craving for enlarged resources wherewith to study human progress. Mr. Spencer had a wide general acquaintance with botany, zoology, and allied studies. The question naturally occurred to him, Where do we find the process of development most completely exemplified from beginning to end, so that we can follow and exhaustively describe its consecutive phases? Obviously in the development of the ovum. There and only there do we get the whole process under our eyes from the first segmentation of the yolk to the death of the matured individual. In other groups of phenomena we can only see a small part of what is going on; they are too vast for us, as in astronomy, or too complicated, as in sociology. Elsewhere our evidences of development are more or less piecemeal and scattered, but in embryology we do get, at any rate, a connected story. So Mr. Spencer took up Von Baer's problem and carried the solution of it much further than the great German naturalist. He showed that in the development of the ovum the change from homogeneity to heterogeneity is accompanied by a change from indefiniteness to definiteness; there are segregations of similarly differentiated units resulting in the formation of definite organs. He further showed that there is a parallel and equally important change from incoherence to coherence; along with the division of labor among the units there is an organization of labor; at first among the homogeneous units there is no subordination—to subtract one would not alter the general aspect; but at last among the heterogeneous organs there is such subordination and interdependence that to subtract anyone is liable to undo the whole process and destroy the organism. In other words, integration is as much a feature of development as differentiation; the change is not simply from a structureless whole into parts, but it is from a structureless whole into an organized whole with a consensus of different functions—and that is what we call an organism. So where Von Baer said that the evolution of the chick is a change from homogeneity to heterogeneity through successive differentiations, Mr. Spencer said that the evolution of the chick is a continuous change from indefinite incoherent homogeneity to definite coherent heterogeneity through successive differentiations and integrations.
But Mr. Spencer had now done something more than describe exhaustively the evolution of an individual organism. He had got a standard of high and low degrees of organization; and the next thing in order was to apply this standard to the whole hierarchy of animals and plants according to their classified relationships and their succession in geological time. This was done with most brilliant success. From the earliest records in the rocks the general advance in types of organization has been an advance in definiteness, coherence, and heterogeneity. The method of evolution in the life-history of the animal and vegetal kingdoms has been like the method of evolution in the life-history of the individual.
To go into the inorganic world with such a formula might seem rash. But as the growth of organization is essentially a particular kind of redistribution of matter and motion, and as redistribution of matter and motion is going on universally in the inorganic world, it is interesting to inquire whether in such simple approaches toward organization as we find there is any approach toward the characteristics of organic evolution as above described. It was easy for Mr. Spencer to show that the change from a nebula into a planetary system conforms to the definition of evolution in a way that is most striking and suggestive. But in studying the inorganic world Mr. Spencer was led to modify his formula in a way that vastly increased its scope. He came to see that the primary feature of evolution is an integration of matter and concomitant dissipation of motion. According to circumstances this process may or not be attended with extensive internal rearrangements and development of organization. The continuous internal rearrangement implied in the development of organization is possible only where there is a medium degree of mobility among the particles, a plasticity such as is secured only by those peculiar chemical combinations which make up what we call organic matter. In the inorganic world, where there is an approach to organization there is an adumbration of the law as realized in the organic world. But in the former what strikes us most is the concentration of the mass with the retention of but little internal mobility; in the latter what strikes us most is the wonderful complication of the transformations wrought by the immense amount of internal mobility retained. These transformations are to us the mark, the distinguishing feature of life.
Having thus got the nature of the differences between the organic and inorganic worlds into a series of suggestive formulas, the next thing to be done was to inquire into the applicability of the law of evolution to the higher manifestations of vital activity—in other words, to psychical and social life. Here it was easy to point out analogies between the development of society and the development of an organism. Between a savage state of society and a civilized state it is easy to see the contrasts in complexity of life, in division of labor, in interdependence and coherence of operations and of interests. The difference resembles that between a vertebrate animal and a worm.
Snch analogies are instructive, because at the bottom of the phenomena there is a certain amount of real identity. But Mr. Spencer did not stop with analogies; he pursued his problem into much deeper regions. There is one manifest distinction between a society and an organism. In the organism the conscious life, the psychical life, is not in the parts but in the whole; but in a society there is no such thing as corporate consciousness: the psychical life is all in the individual men and women. The highest development of this psychical life is the end for which the world exists. The object of social life is the highest spiritual welfare of the individual members of society. The individual human soul thus comes to be as much the center of the Spencerian world as it was the center of the world of mediæval theology; and the history of the evolution of conscious intelligence becomes a theme of surpassing interest.
This is the part of his subject which Mr. Spencer has handled in the most masterly manner. Nothing in the literature of psychology is more remarkable than the long-sustained analysis in which he starts with complicated acts of quantitative reasoning and resolves them into their elementary processes, and then goes on to simpler acts of judgment and perception, and then down to sensation, and so on, resolving and resolving, until he gets down to the simple homogeneous psychical shocks or pulses in the manifold compounding and recompounding of which all mental action consists. Then, starting from that conception of life as the continuous adjustment of inner relations within the organism to outer relations in the environment—a conception of which he made such brilliant use in his Principles of Biology—he shows how the psychical life gradually becomes specialized in certain classes of adjustments or correspondences, and how the development of psychical life consists in a progressive differentiation and integration of such correspondences. Intellectual life is shown to have arisen by slow gradations, and the special interpretations of reflex action, instinct, memory, reason, emotion, and will are such as to make the Principles of Psychology indubitably the most suggestive book upon mental phenomena that was ever written.
Toward the end of the first edition of The Origin of Species, published in 1859, Mr. Darwin looked forward to a distant future when the conception of gradual development might be applied to the phenomena of intelligence. But the first edition of the Principles of Psychology, in which this was so successfully done, had already been published four years before—in 1855—so that Mr. Darwin in later editions was obliged to modify his statement and confess that, instead of looking so far forward, he had better have looked about him. I remember hearing Mr. Darwin laugh merrily over this at his own expense.
This extension of the doctrine of evolution to psychical phenomena was what made it a universal doctrine, an account of the way in which the world, as we know it, has come to be. There is no subject great or small that has not come to be affected by the doctrine, and, whether men realize it or not, there is no nook or corner in speculative science where they can get away from the sweep of Mr. Spencer's thought.
This extension of the doctrine to psychical phenomena is by many people misunderstood. The Principles of Psychology is a marvel of straightforward and lucid statement; but, from its immense reach and from the abstruseness of the subject, it is not easy reading. It requires a sustained attention such as few people can command except on subjects with which they are already familiar. Hence few people read it in comparison with the number who have somehow got it into their heads that Mr. Spencer tries to explain mind as evolved out of matter, and is therefore a materialist. How many worthy critics have been heard to object to the doctrine of evolution that you can not deduce mind from the primeval nebula unless the germs of mind were present already! But that is just what Mr. Spencer says himself. I have heard him say it more than once, and his books contain many passages of equivalent import. He never misses an opportunity for attacking the doctrine that mind can be explained as evolved from matter. But, in spite of this, a great many people suppose that the gradual evolution of mind must mean its evolution out of matter, and are deaf to arguments of which they do not perceive the bearing. Hence Mr. Spencer is so commonly accredited with the doctrine which he so earnestly repudiates.
But there is another reason why people are apt to suppose the doctrine of evolution to be materialistic in its implications. There are able writers who have done good service in illustrating portions of the general doctrine, and are at the same time avowed materialists. One may be a materialist, whatever his scientific theory of things; and to such a person the materialism naturally seems to be a logical consequence from the scientific theory. We have received this evening a communication from Prof. Ernst Haeckel, of Jena, in which he lays down five theses regarding the doctrine of evolution:
1. "The general doctrine appears to be already unassailably founded.
2. "Thereby every supernatural creation is completely excluded.
3. "Transformism and the theory of descent are inseparable constituent parts of the doctrine of evolution.
4. "The necessary consequence of this last conclusion is the descent of man from a series of vertebrates."
So far, very good; we are within the limits of scientific competence, where Prof. Haeckel is strong. But now, in his fifth thesis, he enters the region of metaphysics—the transcendental region, which science has no competent methods of exploring—and commits himself to a dogmatic assertion:
5. "The belief in an 'immortal soul' and in 'a personal God' are therewith" (i. e., with the four preceding statements) "completely ununitable (völlig unwereinbar)."
Now, if Prof. Haeckel had contented himself with asserting that these two beliefs are not susceptible of scientific demonstration; if he had simply said that they are beliefs concerning which a scientific man, in his scientific capacity, ought to refrain from making assertions because Science knows nothing whatever about the subject—he would have occupied an impregnable position. His fifth thesis would have been as indisputable as his first four. But Prof. Haeckel does not stop here. He declares virtually that, if an evolutionist is found entertaining the beliefs in a personal God and an immortal soul, nevertheless these beliefs are not philosophically reconcilable with his scientific theory of things, but are mere remnants of an old-fashioned superstition from which he has not succeeded in freeing himself.
Here one must pause to inquire what Prof. Haeckel means by "a persona] God." If he refers to the Latin conception of a God remote from the world of phenomena and manifested only through occasional interference—the conception that has until lately prevailed in the Western world since the time of St. Augustine—then we may agree with him; the practical effect of the doctrine of evolution is to abolish such a conception. But with regard to the Greek conception entertained by St. Athanasius; the conception of God as immanent in the world of phenomena and manifested in every throb of its mighty rhythmical life; the deity that Richard Hooker, prince of English churchmen, had in mind when he wrote of Natural Law that "her seat is the bosom of God and her voice the harmony of the world"—with regard to this conception the practical effect of the doctrine of evolution is not to abolish but to strengthen and confirm it. For, into whatever province of Nature we carry our researches, the more deeply we penetrate into its laws and methods of action, the more clearly do we see that all provinces of Nature are parts of an organic whole animated by a single principle of life that is infinite and eternal. I have no doubt Prof. Haeckel would not only admit this, but would scout any other view as inconsistent with the monism which he professes. But he would say that this infinite and eternal principle of life is not psychical, and therefore can not be called in any sense "a personal God." In an ultimate analysis, I suspect, Prof. Haeckel's ubiquitous monistic principle would turn out to be neither more nor less than Dr. Büchner's mechanical force (Kraft). On the other hand, I have sought to show—in my little book The Idea of God—that the Infinite and Eternal Power that animates the universe must be psychical in its nature, that any attempt to reduce it to mechanical force must end in absurdity, and that the only kind of monism which will stand the test of an ultimate analysis is monotheism. While in the chapter on Anthropomorphic Theism, in my Cosmic Philosophy, I have taken great pains to point out the difficulties in which (as finite thinkers) we are involved when we try to conceive the Infinite and Eternal Power as psychical in His nature, I have, in the chapter on Matter and Spirit, in that same book, taken equal pains to show that we are logically compelled thus to conceive Him.
One's attitude toward such problems is likely to be determined by one's fundamental conception of psychical life. To a materialist the ultimate power is mechanical force, and psychical life is nothing but the temporary and local result of fleeting collocations of material elements in the shape of nervous systems. Into the endless circuit of transformations of molecular motion, says the materialist, there enter certain phases which we call feelings and thoughts; they are part of the circuit, they arise out of motions of material molecules and disappear by being retransformed into such motions; hence, with the death of the organism in which such motions have been temporarily gathered into a kind of unity, all psychical activity and all personality are ipso facto abolished. Such is the materialistic doctrine, and such, I presume, is what Prof. Haeckel has in mind when he asserts that the belief in an immortal soul is incompatible with the doctrine of evolution. The theory commonly called that of the correlation of forces, and which might equally well or better be called the theory of the metamorphosis of motions, is indispensable to the doctrine of evolution. But for the theory that light, heat, electricity, and nervea ction are different modes of undulatory motion transformable one into another, and that similar modes of motion are liberated by the chemical processes going on within the animal or vegetal organism, Mr. Spencer's work could never have been done. That theory of correlation and transformation is now generally accepted, and is often appealed to by materialists. A century ago Cabanis said that the brain secretes thought as the liver secretes bile. If he were alive to-day, he would doubtless smile at this old form of expression as crude, and would adopt a more subtle phrase; he would say that "thought is transformed motion."
Against this interpretation I have maintained that the theory of correlation not only fails to support it, but actually overthrows it. The arguments may be found in the chapter on Matter and Spirit in my Cosmic Philosophy, published in 1874, and in the essay entitled A Crumb for the Modern Symposium, written in 1877 and reprinted in Darwinism and other Essays. Their purport is, that in tracing the correlation of motions into the organism through the nervous system, and out again, we are bound to get an account of each step in terms of motion. Unless we can show that every unit of motion that disappears is transformed into an exact quantitative equivalent, our theory of correlation breaks down; but when we have shown this we shall have given a complete account of the whole affair without taking any heed whatever of thought, feeling, or consciousness. In other words, these psychical activities do not enter into the circuit, but stand outside of it, as a segment of a circle may stand outside a portion of an entire circumference with which it is concentric. Motion is never transformed into thought, but only into some other form of measurable (in fact, or, at any rate, in theory measurable) motion that takes place in nerve-threads and ganglia. It is not the thought, but the nerve-action that accompanies the thought, that is really "transformed motion." I say that, if we are going to verify the theory of correlation, it must be done (actually or theoretically) by measurement; quantitative equivalence must be proved at every step; and hence we must not change our unit of measurement; from first to last it must be a unit of' motion: if we change it for a moment, our theory of correlation that moment collapses. I say, therefore, that the theory of correlation and equivalence of forces lends no support whatever to materialism. On the contrary, its manifest implication is that psychical life can not be a mere product of temporary collocations of matter.
The argument here set forth is my own. When I first used it I had never met with it anywhere in books or conversation. Whether it has since been employed by other writers I do not know, for during the past fifteen years I have read very few books on such subjects. At all events, it is an argument for which I am ready to bear the full responsibility. Some doubt has recently been expressed whether Mr. Spencer would admit the force of this argument. It has been urged by Mr. S. H. Wilder, in two able papers published in the New York Daily Tribune, June 13 and July 4, 1890, that the use of this argument marks a radical divergence on my part from' Mr. Spencer's own position. It is true that in several passages of First Principles there are statements which either imply or distinctly assert that motion can be transformed into feeling and thought—e. g., " Those modes of the Unknowable which we call heat, light, chemical affinity, etc., are alike transformable into each other, and into those modes of the Unknowable which we distinguish as sensation, emotion, thought: these, in their turns, being directly or indirectly retransformable into the original shapes " (First Principles, second edition, 1867, p. 217); and again it is said "to be a necessary deduction from the law of correlation, that what exists in consciousness under the form of feeling is transformable into an equivalent of mechanical motion," etc. (First Principles, second edition, p. 558). Now, if this, as literally interpreted, be Mr. Spencer's deliberate opinion, I entirely dissent from it. To speak of quantitative equivalence between a unit of feeling and a unit of motion seems to me to be talking nonsense—to be combining terms which severally possess a meaning into a phrase which has no meaning. I am, therefore, inclined to think that the above sentences, literally interpreted, do not really convey Mr. Spencer's opinion. They appear manifestly inconsistent, moreover, with other passages in which he has taken much more pains to explain his position (e. g., Principles of Psychology, pp. 158-161, 616-627). In the sentence of p. 558 of First Principles, Mr. Spencer appears to me to mean that the nerve-action, which is the objective concomitant of what is subjectively known as feeling, is transformable into an equivalent of mechanical motion. When he wrote that sentence perhaps he had not shaped the case quite so distinctly in his own mind as he had a few years later, when he made the more elaborate statements in the Psychology. Though in these more elaborate statements he does not assert the doctrine I have here maintained, yet they seem consistent with it. When I was finishing the chapter on Matter and Spirit, in my room in London one afternoon in February, 1874, Mr. Spencer came in, and I read to him nearly the whole chapter, including my argument from correlation above mentioned. He expressed warm approval of the chapter, without making any specific qualifications. In the course of the chapter I had occasion to quote a passage from the Psychology (vol. i, p. 158; cf. Cosmic Philosophy, vol. ii, p. 444), in which Mr. Spencer twice inadvertently used the phrase "nervous shock" where he meant "psychical shock." As his object was to keep the psychical phenomena and their cerebral concomitants distinct in his argument, this colloquial use of the word "nervous" was liable to puzzle the reader, and give the querulous critic a chance to charge Mr. Spencer with the materialistic implications which it was his express purpose to avoid. Accordingly, in my quotation I changed the word "nervous" to "psychical," using brackets and explaining my reasons. On showing all this to Mr. Spencer, he desired me to add in a foot-note that he thoroughly approved the emendation.
I mention this incident because our common, every-day speech abounds in expressions that have a materialistic flavor; and sometimes in serious writing an author's sheer intentness upon his main argument may lead him to overlook some familiar form of expression which, when thrown into a precise and formal context, will strike the reader in a very different way from what the author intended. I am inclined to explain in this way the passages in First Principles which are perhaps chiefly responsible for the charge of materialism that has so often and so wrongly been brought up against the doctrine of evolution.
As regards the theological implications of the doctrine of evolution, I have never undertaken to speak for Mr. Spencer; on such transcendental subjects it is quite enough if one speaks for one's self. It is told of Diogenes that, on listening one day to a sophistical argument against the possibility of motion, he grimly got up out of his tub and walked across the street. Whether his adversaries were convinced or not, we are not told. Probably not; it is but seldom that adversaries are convinced. So, when Prof. Haeckel declares that belief in a "personal God" and an "immortal soul" are incompatible with acceptance of the doctrine of evolution, I can only say, for myself—however much or little the personal experience may be worth—I find that the beliefs in the psychical nature of God and in the immortality of the human soul seem to harmonize infinitely better with my general system of cosmic philosophy than the negation of these beliefs. If Prof. Haeckel, or any other writer, prefers a materialistic interpretation, very well. I neither quarrel with him nor seek to convert him; but I do not agree with him. I do not pretend that my opinion on these matters is susceptible of scientific demonstration. Neither is his. I say, then, that his fifth thesis has no business in a series of scientific generalizations about the doctrine of evolution.
Far beyond the limits of what scientific methods, based upon our brief terrestrial experience, can demonstrate, there lies on every side a region with regard to which Science can only suggest questions. As Goethe so profoundly says: "Willst du ins Unendliche streiten, Geh' nur im Endlichen nach alien Seiten." 
It is of surpassing interest that the particular generalization which has been extended into a universal formula of evolution should have been the generalization of the development of an ovum. In enlarging the sphere of life in such wise as to make the whole universe seem actuated by a single principle of life, we are introduced to regions of sublime speculation. The doctrine of evolution, which affects our thought about all things, brings before us with vividness the conception of an ever-present God not an absentee God who once manufactured a cosmic machine capable of running itself except for a little jog or poke here and there in the shape of a special providence. The doctrine of evolution destroys the conception of the world as a machine. It makes God our constant refuge and support, and Nature his true revelation; and when all its religious implications shall have been set forth, it will be seen to be the most potent ally that Christianity has ever had in elevating mankind.
- Address before the Brooklyn Ethical Association, May 31, 1891.
- See, for example, Principles of Psychology, vol. ii, pp. 145-162.
- See also Excursions of an Evolutionist, pp. 274-282.
- ["If thou wouldst press into the infinite, go but to all parts of the finite."]