William Keith Brooks

“ Most naturalists not only believe that, if we could trace back the history of life, we should find each group bearing evidence of wider and wider relationship as we receded from the present time, but they also believe that we should ultimately find that every form of life is related to every other in such a way as to show that, in the remote past, they all met in a single starting-point—the common ancestor of all living things. ”

“ Hardly anything can be of greater value to a man of theory and speculation, who employs himself, not in collecting materials of knowledge by observation, but in working them up by processes of thought into comprehensive truths of science and laws of conduct, than to carry on his speculations in the companionship, and under the criticism, of a really superior woman. There is nothing comparable to it for keeping his thoughts within the limits of real things, and the actual facts of nature. ”

“ We are apt to confine our attention to the subjective side of human advancement, and to neglect the structural side, and at the same time to neglect the subjective side of the evolution of the lower forms of life, and to confine our attention to the structural side, but of course no one can doubt that a new habit is represented by a new specialization of structure, and is transmitted like any other peculiarity by heredity. ”

“ Definitions are valuable and indispensable aids to study, and, as long as their necessary lack of agreement with the reality is kept in mind, they can do no harm; but the history of science warns us to be constantly on our guard, lest distinctions which seem to be sharp and absolute, when stated in words, come to be regarded as having as real an existence in Nature as in words, and we thus come, in the words of Bacon, to exchange "things for words, reason for insanity, and the world for a fable." ”

“ It is plain, from what has been said, that the separation of organisms into two great group—animals and plants—is convenient and natural, and that the distinctions between them are real but not absolute; and it is possible to define, that is give, all the characteristics which are distinctive of an animal, without implying or assuming that all animals conform with the definition to the same degree, or that no plant shares any of the characteristics. ”

“ Even the individual peculiarities of the parents, intellectual and moral as well as physical, are now known to be hereditary. Since this holds true of any other animal or plant, we must recognize the universality of the law of heredity, but we must not overlook the equally well-established fact that each organism is the resultant of this law and another, the law of variation. The child is like its parents, but not exactly like them. It is not even a compound of characteristics found in one or the other of them, but has individual peculiarities of its own ”

“ The future history of our race will be a continuation of the one line as well as of the other, or, rather, one is included by the other. The end of the study of history is not the discovery of what has been in the past, but the discovery of general laws and causes that shall enable us to foresee what is to take place in the future; but this sort of historical knowledge, the wisdom of history, does not come from observation, but from reflection upon the inner relations, the causes and effects of phenomena—from a weighing of the probabilities between one interpretation and another ”

“ While we fully recognize the insignificance of the merely animal differences between the sexes, as compared with their intellectual and moral influence, it is none the less true that the origin of the latter is to be found in the former; in the same manner—to use a humble illustration—that the origin of the self-denying, disinterested devotion of a dog to his master is to be found in that self-negation which is necessary in order that a herd of wolves may act in concert under a leader, for the general good. ”

“ But, even if design can be shown, it does not follow that the adaptation is the fruit of direct creative interposition; and the fact that it is not always perfect—that, perfect as the wing is in most birds, more than one species has become extinct in recent times, on account of the rudimentary and useless state of the wings—has been held by many to be sufficient proof that the adaptation was not produced in this way.
We shall be able to take a more fair view of this question after we have examined the ultimate nature—the homology, as it is called—of the organs of flight. ”

“ If this adjustment constitutes vitality, and if natural selection furnishes an explanation of the manner in which the adjustment has been brought about, have we not, in the law of natural selection, an explanation of the origin of life?—not of course of the origin of the matter of life, nor of the changes of which life is made up, nor of the production of living beings, but of the origin of those attributes by which living things are especially characterized, and in which they differ from all other forms of existence. ”

“ The slight individual differences are so overshadowed by the much more conspicuous resemblances due to heredity—with which they compare about as the green buds at the tips of the twigs of a large tree compare with the hard wood of the trunk and branches, the growth of previous years—and they are so fluctuating and inconstant, that their importance may easily escape attention. ”

“ If no fossils were known, the facts of comparative anatomy, of embryology, and of geographical distribution would be enough to satisfy us that the living things known to us are the divergent descendants of more generalized ancestors, and that their relationships can be most exactly expressed by a system of converging lines, which meet and form larger branches to represent the extinct ancestors from which our divergent species are descended. The evidence is circumstantial, and only leads to general conclusions, and a complete series of fossil forms is the only absolute proof which we could have ”

“ Those who acknowledge the weight of my argument, as applied to evolution in the past, may, however, question its applicability to the human evolution of the future. It may fairly be urged that while we grant that the course of evolution from the lower forms of life up to rational man has been by the slow process of variation and heredity, we have now passed into a new order of things, and the great advances of the human race have been and are now brought about by the much more rapid and totally dissimilar process of intelligent education. ”

“ If you say that all natural knowledge is simply probable, and open to the possibility of error, give us proofs which are as direct as those which are furnished by the physical sciences, instead of the general and circumstantial evidence which you adduce. The student of physics does not ask us to believe that all bodies attract each other according to the law of inverse squares until he has shown us that he is able to prove that every body we bring him does behave in this way ”

“ The evidence is often so hard to read that the accounts of the best observers are contradictory, and in many cases it is so scanty and incomplete that it must be submitted to a severely critical process of comparison, analysis, cross-examination, and elimination, before a general conclusion can be reached. The field is so vast, the amount of evidence so great, and special features are so numerous, that the thorough discussion of the problem in all its bearings will furnish employment for the most acute and comprehensive powers of analysis for an indefinite period ”

“ Throughout the whole course of the evolution of one of the higher organisms each variation which served to bring about a closer harmony between the organism and its environment, and was accordingly preserved by natural selection, and added on to the series of hereditary structures and functions, was in its subjective aspect the experience of a new external connection, a new step in the recognition of natural law, an advance in scientific knowledge. Human advancement is of course widely different from the slow progress of the lower forms of life, but it is fundamentally the same. ”

“ Among the lowest organisms, animal and vegetable, multiplication is usually by the various forms of asexual generation, budding or fission, or cell-multiplication—an organism which has by ordinary growth increased in size beyond the limit of exact harmony with its environment, dividing in this way into two, like each other as well as like their parent. In this way the preservation of the established characteristics of the species—heredity—is provided for, but in order that progress should take place, by the preservation of favorable varieties, variation must also be provided for. ”

“ In order to trace the origin and significance of the differences which attain to such complexity and importance in the human race, we must carry our retrospect back far beyond the beginning of civilization, and trace the growth and meaning of sex in the lower forms of life. ”

“ In almost every case where we are called upon to form a judgment, and to act upon it, the premises are so uncertain, the conditions of the problem so numerous and so little known, and its relations to other things admit of so much variation, that our conclusion can be nothing but a probability ”

“ As the field of human knowledge widens in all directions, as society becomes more complex, and as the points of contact between man and his inorganic environment multiply, the amount of general education which each individual must receive before he is in a position to hold his own, and to guide himself rationally in all the emergencies of life, and to enjoy his share of the benefits which our intellectual advancement has placed within his reach, increases in a geometrical progression, and the amount of time demanded for general liberal education increases in the same ratio. ”

“ You have certainly made out a very ingenious story, and have brought together a mass of evidence which appears to render your view very probable, but you have not shown that no other explanation is possible, and, as we do hold quite a different opinion upon evidence which is satisfactory to us, you must be mistaken. We are open to conviction, and are not unreasonable, but we must have proofs which leave no room for doubt, for as long as there is a chance that you are wrong we must hold to our old view. ”

“ The animals with which we are most familiar, the mammals and birds, are born in substantially the form which they will have when they reach maturity. They breathe the same medium; they employ the same organs of locomotion, in the same way; they require the same or nearly the same kind of food, and their habits and surroundings are the same as they will be during mature life, or at least the differences are slight and insignificant, and the adult is little more than the young animal grown to its full size, and with sexual characteristics, and able to reproduce its kind. ”

“ When descriptive embryology was in its infancy, it so frequently happened that a knowledge of younger stages threw a flood of light upon the affinities of doubtful forms, that naturalists felt a growing hope that here was the true key to the natural system of classification, and that all they needed for reading the riddle was a thorough knowledge of the whole course of development of each form of life. ”

“ I think that this illustration gives us a fair statement of the value of the evidence for evolution which is furnished by paleontology. There is an absolute and total lack of direct proof, and there must be by the nature of the case, so there is no room to hope for the conversion of any one who is determined to reject the theory as long as doubt is possible; but the end of science is not to proselyte but to discover, and the circumstantial evidence converges in such a way as to give in this case every assurance of substantial accuracy. ”

“ Finally, I wish to call attention to the fact that natural selection is constantly acting through the law of the survival of the fittest, in such a way as to bring each organism into more and more perfect harmony with its environment; that is, it is constantly bringing about a more and more exact, definite, and perfect adjustment between external and internal relations. ”

“ He is in no need of doing rapidly what he does; what he rather needs is patience to work on slowly until imperfect lights have become perfect, and a conjecture has ripened into a theorem. For those, on the contrary, whose business is with the fugitive and perishable—with individual facts, not kinds of facts—rapidity of thought is a qualification next only in importance to the power of thought itself. He who has not his faculties under immediate command in the contingencies of action might as well not have them at all. ”

“ While the number of factors involved in a morphological problem is vastly greater than that of those which bear upon any problem into which life does not enter, and while the relations between these factors vary, in closely allied cases, in a way which has no parallel outside life-science, the problems of general morphology are still vastly simpler than those of society or of morality, or of almost any other department of human conduct, although they are like them in kind, and supply the same sort of evidence. ”

“ In so far as the contraction of a muscle is simply a change, it is without doubt purely physical; but in the adjustment of this change to a relation between external changes, in its adaptation to a purpose, we have something which has no parallel except in living things, and perhaps some of man's contrivances, such as the automatic governor of the steam-engine. Living things are distinguished from those which have not life by their adjustment, and life consists in this adjustment. ”