What Evolution Is and What It Is Not (1897)

I found this interesting and still surprisingly modern essay by David Starr Jordan in 1897, at William Tozier's blog, where he had scanned it from a journal called The Arena. They had some good public discussion journals at the time.

So I took his scan and OCR'd and corrected it, and put it here. It is amazing how well Jordon managed to avoid the usual errors, and correct those that are with us still, so long ago.

The essay is beneath the fold. I left the headers in.

THE ARENA.

Vol. XVIII.AUGUST, 1897.No. 93.

EVOLUTION: WHAT IT IS AND WHAT IT IS NOT.¹

BY DR. DAVID STARR JORDAN,

President of Leland Stanford Junior University.

I. WHAT EVOLUTION IS.

THIS is the age of evolution. The word is used by many men in many senses, and still oftener perhaps in no sense at all. By some it is spoken with a haunting dread as though it were another name for the downfall of religion and of social stability. Still others speak it glibly and joyously as though progress and freedom were secured by the more use of the name. "The word evolution (Entwickelung)," says a German writer, "fills the vocal chords more perfectly than any other word." It explains everything, and "puts the key to the universe into one's vest pocket."

So various has been the use of the word, so rarely is this use associated with any definite idea, that one hesitates to call himself an evolutionist. "Evolution" and "evolutionist" are almost ready to be cast into that "limbo of spoiled phraseology" which Matthew Arnold has found necessary for so many words in which other generations have delighted, and which they have soiled or spoiled by careless usage.

But as the word evolution is not yet put away, as it is the bugbear of many good people, and the "religion" of as many more equally good, it may be worth while to consider what it still means, and what it does not mean. For if we that use the word can agree on a definition, half our quarrel is over.

It seems to me that the word evolution is now legitimately used in four different senses. It is the name of a branch of

¹ Address before the Starr King Fraternity of Oakland, Cal.

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science. It is a theory of organic existence. It is a method of investigation, and it is the basis of a system of philosophy.

The Science of Organic Evolution, or Bionomics. As a science, evolution is the study of changing beings acted upon by unchanging laws. It is a matter of common observation that organisms change from day to day, and that day by day some alteration in their environment is produced. It is a matter of scientific investigation that these changes are greater than they appear. They affect not only the individual animal or plant, but they affect all groups of living things, classes or races or species. No character is permanent, no trait of life without change. And as the living organism or group of organisms is undergoing alteration, so does change take place in the objects of the physical world about them. "Nothing endures," says Huxley, "save the flow of energy and the rational order that pervades it." The structures and objects change their forms and relations, and to forms and relations once abandoned they never return. But the methods of change are, so far as we can see, immutable. The laws of life, the laws of death, and the laws of matter never change. If the invisible forces which rule all visible things are themselves subject to modification and evolution, we have not detected it. Its cosmic movements are so fine as to defy human observation and computation. In the control of the universe we find no trace of "variableness nor shadow of turning." "it is the law of heaven and earth, whose way is solid, substantial, vast, and unchanging.".

But the things we know do not endure. Only the shortness of human life allows us to speak of species or even of individuals as permanent entities. The mountain chain is no more nearly eternal than the drift of sand. It endures beyond the period of human observation. It antedates and outlasts human history. So does the species of animal or plant outlast and antedate the lifetime of one man. Its changes are slight even in the lifetime of the race. Thus the species, through the persistence of its type among its changing individuals, comes to be regarded as something which is beyond modification, unchanging so long as it exists.

"I believe," said the rose to the lily in the parable "I

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believe that our gardener is immortal. I have watched him from day to day since I bloomed, and I see no change in him. The tulip who died yesterday told me the same thing."

As a flash of lightning in the duration of the night, so is the life of man in the duration of nature. When one looks out on a storm at night, he sees for an instant the landscape illumined by the lightning-flash. All seems at rest. The branches in the wind, the flying clouds, the falling rain are all motionless in this instantaneous view. The record on the retina takes no account of change, and to the eye the change does not exist. Brief as the lightning-flash in the storm is the life of man compared with the great time-record of life upon earth. To the untrained man who has not learned to read these records, species and types in life are enduring. Thus arose the theory of special creation and permanence of type, a theory which could not persist when the fact of change and the forces causing it came to be studied in detail.

But when man came to study the facts of individual variation and to think of their significance, the current of life no longer seemed at rest. Like the flow of a mighty river, never returning, ever sweeping steadily on, is the movement of all life. The changes in human history are only typical of the changes that take place in all living creatures. In fact, human history is only a part of one great life-current, the movement of which is everywhere governed by the same laws, depends on the same forces, and brings about like results.

The facts and generalizations of change constitute the subject-matter of evolution. And as the fact of life is a fundamental one, and in some degree modifies all phenomena which it concerns, we have as the central axis of the science in question, the study of organic evolution. In fact, while inorganic evolution, or orderly change in environment, exists, we do not know to what degree the laws and forces of organic evolution can be reduced to the same terms of expression. The theory of the essential and necessary unity of life and non-life, of mind and matter, is still a matter of philosophical speculation only. We can neither prove the truth of Monism, nor understand it; nor is the contrary hypothesis either comprehensible or credible. The fundamental unity of organic evolution and inorganic evo-

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lution is yet to be proved, while the laws which govern living matter are certainly in part peculiar to life. For this reason the evolution of astronomy, of dynamic geology, of geography, as well as the purely hypothetical evolution of chemistry, must be separated from life evolution. Cosmic evolution and organic evolution show, or seem to show, some divergence from each other. There are some elements which are not held in common, or which, at least, are not identical when measured in human terms. For the latter, the science of organic evolution, there is therefore certainly need of a distinctive term. This has been lately furnished by Professor Patrick Geddes, who has chosen the term bionomics. Bionomics (βίος, life; νόμος, law or custom) is the science which treats of the changes in life-forms, and of the laws and forces on which these changes depend.

Even as thus restricted organic evolution, or bionomics, is the greatest of the sciences, including in its subject-matter, not only all natural history, not only processes like cell-division and nutrition, not only the laws of heredity, variation, natural selection, and mutual help, but all matters of human history, and the most complicated relations of civics, economics, or ethics. In this enormous science no fact can be without a meaning, and no fact or its underlying forces can be separated from the great forces whose interaction from moment to moment writes the great story of life.

And as the basis to the science of bionomics, as to all other science, must be taken the conception that nothing is due to chance or whim. Whatever occurs does so as the resultant of moving forces. Could we know and estimate these forces, we should have, so far as our estimate is accurate and our logic perfect, the gift of prophecy. Knowing the law, and knowing the facts, we should foretell the results. To be able in some degree to do this is the art of life. It is the ultimate end of science, which finds its final purpose in human conduct.

"A law," according to Darwin, "is the ascertained sequence of events." The necessary sequence of events it is, in fact, but man knows nothing of what is necessary, only of what has been ascertained to occur. Because human observation and logic can be only partial, no law of life can be fully stated. Because the
processes of the human mind are human, with organic limita-

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tions, the study of the mind itself becomes a part of the science of bionomics. For it is itself an instrument or a combination of instruments by which we acquire such knowledge of the world outside of ourselves as may be needed in the art of living, in the degree in which we are able to practise that art.

The necessary sequence of events exists, whether we are able to comprehend it or not. The fall of a leaf follows fixed laws as surely as the motion of a planet. It falls by chance because its short movement gives us no time for observation and calculation. It falls by chance because, its results being unimportant to us, we give no heed to the details of its motion. But as the hairs of our head are all numbered, so are numbered all the gyrations and undulations of every chance autumn leaf. All processes in the universe are alike natural. The creation of man or the growth of a state is as natural as the formation of an apple or the growth of a snowbank. All are alike supernatural, for they all rest on the huge unseen solidity of the universe, the imperishability of matter and the immanence of law.

We sometimes classify sciences as exact and inexact, in accordance with our ability exactly to weigh forces and results. The exact sciences deal with simple data accessible and capable of measurement. The results of their interactions can be reduced to mathematics. Because of their essential simplicity, the mathematical sciences have been carried to great comparative perfection. It is easier to weigh an invisible planet than to measure the force of heredity in a grain of corn. The sciences of life are inexact, because the human mind can never grasp all their data. Nor has the combined effort of all men, the flower of the altruism of the ages, that we call science been able to make more than a beginning in this study. But however incomplete our realization of the laws of life, we may be sure that they are never broken. Each law is the expression of the best possible way in which causes and results can be linked. It is the necessary sequence of events, therefore the best sequence, if we may imagine for a moment that the human words "good" and "bad" are applicable to world-processes. The laws of nature are not executors of human justice. Each one has its own operation, and no other. Each represents its own tendency towards cosmic order. A law in this sense can

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not be "broken." A broken law would be a discarded universe. If God should wink at a single act of injustice," says the Arab proverb, "the whole universe would shrivel up like a castoff snakeskin." If God should wink at any violated law the universe would vanish.

Not long ago, in an examination in a theological seminary, the question was asked of the candidates for the ministry, "Is it right to pray for a change of season?" The candidates thought that it was not, for the relations which produce winter and summer are fixed in the structure of the solar system and cannot be altered for man's pleasure or man's need. "Is it right to pray for rain?" The candidates generally thought that it was, because the conditions of rain are so unstable that a little change in one way or another would bring rain or fair weather, and that it was proper to ask for such change, as it did not concern the economy of the universe.

The third question was: "When the signal service of the United States is well established, so that weather conditions are perfectly known, will it then be right to pray for rain?" And the candidates for the ministry could not tell, for they began to see that even simple changes of weather may have the strength of the whole universe behind them. It has never yet rained when by any possibility it could do otherwise. It has never failed to rain when rain was possible. The Spanish padres in California, wise in their generation, allowed prayers for rain only in winter, when the wind was in the south. The wind is only in the south when the air is affected by a cyclonic movement, and this in the California winter means rain.

We hear good men say sometimes that the crying need of this strong and sceptical age is that it may see some law of nature definitely broken, that it may rain when rain is impossible, or that some burning bush may, unconsuming, proclaim that the force which is behind all law is also above it and can break or repeal all laws at will.

Emerson somewhere speaks of the purpose in life "To be sound and solvent." As his life was in all ways "sound and solvent," perhaps such rule of conduct was his own. But one may say, That is only a rule. The man himself should be all rules and requirements of his own establishment. Let Mr.

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Emerson show that his life is above his principles. Let him break these rules. Let him be "unsound and insolvent" for a time. Then only will his greatness appear.

The laws of nature are the expression of the infinite soundness and solvency. They will not be broken, nor through their unsoundness and insolvency will the "heavens roll away as a scroll," nor "the universe shrivel up as a castoff snakeskin."

In the growing recognition of law has been the progress of science. From the casting aside of human notions of chance and whim the "warfare of science" has had its rise. For every event carried over into the realm of law some man has given his life. As the Panama railroad is said to have cost the life of a man for every cross-tie, so has every step in the progress of science. And such men!

Many a time in the growth of humanity has it been necessary that the wisest, clearest, most humane, should die on the stake or the gibbet or the cross, that men should come to realize the power of an idea; that they should know the value of truth.

Evolution as a Theory of Organic Development, or Darwinism. In a different sense the word evolution is applied to the theory of the origin of organs and of species by divergence and development. This theory teaches that all forms of life now existing or that have existed on the earth have sprung from a common stock, which has undergone change in a multitude of ways and under varied conditions, the forces and influences producing such change being known as the "factors of organic evolution." All characters and attributes of species and groups have developed with changing conditions of life. The homologies among animals are the result of common descent. The differences are due to various influences, chief among these being competition in the struggle for existence between individuals and between species, whereby those best adapted to their surroundings lived and reproduced their kind.

This theory is now the central axis of all biological investigation in all its branches, from ethics to histology, from anthropology to bacteriology. In the light of this theory every peculiarity of structure, every character or quality of individual or species, has a meaning and a cause. It is the work of the investigator to find this meaning as well as to record the fact.

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"One of the noblest lessons left to the world" by Darwin is this, Mr. Frank Cramer tells us,—"this, which to him amounted to a profound, almost religious, conviction, that every fact in nature, no matter how insignificant, every stripe of color, every tint of flowers, the length of an orchid's nectary, unusual height it a plant, all the infinite variety of apparently insignificant things, is full of significance. For him it was an historical record, the revelation of a cause, the lurking-place of a principle."

According to the theory of evolution every structure of today finds its meaning in some condition of the past. The inside of an animal tells what it really is, for it bears the record of heredity. The outside of an animal tells where its ancestors have been, for it bears record of concessions to environment. Similarity in essential structure is known as homology. By the theory of evolution homology, wherever it is found, is proof of blood-relationship.

The theory of organic evolution through natural law was first placed on a stable footing by the observations and inductions of Darwin. It has therefore been long known as Darwinism, although that term has been usually associated with the recognition of natural selection as the great motive power in organic change. Darwinism was at first regarded as a "working hypothesis." It is now an integral part of biological science, because all opposing hypotheses have long since ceased to work. It is as well attested as the theory of gravitation, and its elements are open to less doubt. All investigations in biology must assume it, as without it most such investigations would be impossible. Naturalists could no more go back to the old notion of special creation for each species and its organs than astronomers could go back to the old notion of guiding angels as directors of planetary motion. Without the theory of organic development through natural selection, the biological science of today would be impossible.

Evolution as a Method of Study. In a third sense the word evolution is applied to a method of investigation. It is the study of present conditions in the light of the past. The preliminary work of science is the descriptive part. This involves accuracy of observation and precision of statement, but makes

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no great demands on the powers of logical analysis and synthesis. The easy work of science is largely already done. Those who would continue investigation must study not only facts and structures, but the laws that govern them. In the words of John Fiske, "Whether plants or mountains or mollusks or subjunctive moods or tribal confederacies be the things studied, the scholars who have studied them most fruitfully were those who have studied them as phases of development. Their work has directed the current of thought." The most difficult problems in life are susceptible of more or less perfect solution if approached by the method of evolution. They cannot be even stated as problems in any other terms. In every science worthy of the name the history of origins and the study of developing forces must take a leading part.

Evolution as a System of Cosmic Philosophy. In a fourth sense the word evolution has been applied to the philosophical conceptions to which the theory of evolution gives rise. Philosophy is not truth. When it is so it becomes science. At the best it points the way to truth. The broader the inductive basis of any system of philosophy, the greater its value as an intellectual help. The system of Herbert Spencer, the greatest exponent of the philosophy of evolution, is based wholly on the results of scientific investigation. It consists of a series of more or less broad and more or less probable deductions from the facts and laws already known. Systems like these, which rest on scientific knowledge, do not rise high above it. They can therefore be revised or rewritten as knowledge increases. They provide the means for their own correction. Systems resting on aphorisms or assumptions or definitions must disappear as knowledge increases.

Philosophy is never wholly identical with truth. The partial truth which it may contain becomes wholly error with the advance of science. The growth of exact knowledge transforms the truth in philosophy into science, leaving the absolute falsehood as the final residuum.

From this necessary fact comes the ultimate decay of all creeds or philosophic formulae. Throughout the ages science and philosophy have been in conflict. Science is the same to all minds capable of grasping its conclusions. Philosophy changes

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with the point of view. It is the evanescent perspective in which the facts and phenomena of the universe are seen. This can never be the same under changing times and conditions. With the larger knowledge of tomorrow, there will be large modifications in the accepted philosophy of evolution. Each succeeding generation will give to the applications of the laws of organic life a different philosophical expression.

II. WHAT EVOLUTION IS NOT.

In these four senses the word evolution is used with some degree of accuracy. But in the current literature of the day the word has many other meanings, some of them very far from any just baths. Some things which evolution is not we may here notice briefly.

Evolution is not a theory that "man is a developed monkey." The question of the immediate origin of man is not the central or overshadowing question of evolution. This question offers no special difficulties in theory, although the materials for exact knowledge are in many directions incomplete. Homologies more perfect than those connecting man with the great group of monkeys could not exist. These imply the blood-relationship of the human race with the great host of apes and monkeys. As to this there can be no shadow of a doubt. And as similar homologies connect man with all members of the group of mammals, similar blood-relationship must exist. And homologies, less close but equally unmistakable, connect all backboned animals one with another; and the lowest backboned types are closely joined to wormlike forms not usually classed as vertebrates.

It is perfectly true that, with the higher or anthropoid apes, the relations with man are extremely intimate. But man is not simply "a developed ape." Apes and men have diverged from the same primitive stock, apelike, manlike, but not exactly the one or the other. No apes or monkeys now extant could apparently have been ancestors of primitive man. None can ever "develop" into man. As man changes and diverges, race from race, so do they. The influence of effort, the influence of surroundings, the influence of the sifting process of natural selection, acts upon them as it acts upon man.

The process of evolution is not progress, but better adaptation

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to conditions of life. As man becomes fitted for social and civic life, so does the ape become fitted for life in the treetops. The movement of monkeys is towards "simianity," not humanity. The movement of cat-life is towards felinity, that of the dog-races towards caninity. Each step in evolution upward or downward, whatever it may be, carries each species or type farther from the primitive stock. These steps are never retraced. For an ape to become a man he must go back to the simple characters of the simple common type from which both have sprung. These characters are shown in the ape-baby and in the human embryo in its corresponding stages. For ancestral traits lost in the adult are preserved in the young. This comes through the operation of the great force of race-memory, we call heredity.

Evidence of biology points to the descent of all mammals, of all vertebrates, of all animals, of all organic beings, from a common stock. Of all the races of animals, the anthropoid apes are nearest man. Their divergence from the same stock must be comparatively recent. Man is the nomadic, the apes the arboreal, branch of the same great family.

Evolution does not teach that all or any living forms are tending towards humanity. It does not teach, as in Bishop Wilberforce's burlesque, "that every favorable variety of the turnip is tending to become man." it is not true that evolutionists expect to find, as Dr. Seelye has affirmed, "the growth of the highest alga into a zoöphyte, a phenomenon for which sharp eyes have sought, and which is not only natural but inevitable on the Darwinian hypothesis, and whose discovery would make the fame of any observer."

It is no wonder that a clear thinker should have rejected "the Darwinian hypothesis," when stated in such terms as this. The line of junction in evolution is always at the bottom. It is the lowest mammals which approach the lowest reptiles. It is the lower types of plants which approach the lower types of animals. It would be the lowest alga, to use Dr. Seelye's illustration, which would be transmutable into the lowest zoophyte. It is the unspecialized, undifferentiated type from which branches diverge in different ways. Humanity is not the "goal of evolution," not even that of human evolution. There will be no second "creation of man," except from man's own loins. There

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will not be a second Anglo-Saxon race, unless it has the old Anglo-Saxon blood in its veins.

Adaptation by divergence—for the most part by slow stages—is the movement of evolution. While occasional leaps or sudden changes occur in the process, they are by no means the rule. In most cases of "saltatory evolution," the suddenness is in appearance only. It comes from our inability to trace the intermediate stages. When an epoch-making character is acquired, as the wings of a bird or the brain of man, the process of readjustment of other characters goes on with greatly increased rapidity. But this rapidity of evolution is along the same lines as the slower processes. Radical changes from generation to generation never occur. We do not expect to find birds arising from a "flying-fish in the air, whose scales are disporting into feathers." A flying-fish is no more of the nature of a bird than any other fish is. A cow will never give birth to a horse, nor a horse to a cow. The slow operation of existing causes is the central fact of organic evolution, as it is of the evolution of mountains and valleys. Seasons change as the relations which produce them change. But midsummer never gives way to midwinter in an instant. Nor does the child in an instant become a man, though in some periods of growth epoch-marking causes may make development more rapid. Life is conservative. The law of heredity is the expression of its conservatism. It changes slowly, but it must constantly change, and all change is by necessity divergence.

There is in nature no single "law of progress," nor is progress in any group a necessity regardless of conditions. That which we call progress rests simply on the survival of the better adapted, their survival being accompanied by their reproduction. Those that live repeat themselves. The "innate tendency towards progression" of the early evolutionists is a philosophic myth. Progress and degeneration are alike the resultants of the various forces at work from generation to generation on and within a race or species. The same forces which bring progress to a group under one set of conditions will bring degradation under another. In their essence the factors of evolution are no more laws of progress than the attraction of gravitation is. Cosmic order comes from gravitation. Organic order comes from the factors of evolution. Evolution is simply orderly change.

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Evolution is not Spontaneous Generation. There is no necessary connection between the one theory and the other. Spontaneous generation, or birth without parentage, on the part of small or useless creatures was accepted in early times without question. As men began to observe these animals more carefully, the fact of their spontaneous generation was doubted. A great step was made when it was found that to screen meat from flies would protect it from maggots. A greater step came in our own time when it was proved that to screen infusions from air dust is to protect them from putrefaction or fermentation. Fermentation is "life without air." it is the decomposition of sugar by minute creatures who disintegrate it in their life processes. Putrefaction and decay are also the same in nature. There is literal truth in Carlyle's statement that there is still force in a fallen leaf, "else how could it rot?" It is the force of the minute organisms hidden in the leaf, and whose life is the leaf's decay. The decay and death of men from contagious diseases is known to be due to life processes of minute organisms, as is the gangrene which follows unskilful surgery. The study of the "fauna and flora" within living organisms has now become a science of itself, demanding the greatest care in observation and the most complete of appliances. "Omne vivum ex vivo," "all life from life," was an aphorism of the naturalists of a century or two ago. It was to them a new and broad generalization. It has not yet been set aside. The classic experiments of Tyndall show that this law applies to all creatures we have yet recognized or classified. As far as science can tell, spontaneous generation is still a myth, having no basis in observation, no warrant in experiment. It remains as a pure deduction from the philosophical conception of Monism, incapable of proof, insusceptible of refutation. The argument for it is chiefly this: Life exists on a globe once lifeless. How did life begin? If not through spontaneous generation, how did it come? Must it not have been by the operation of those laws and forces which through all time change lifeless into living matter? Very likely, but we do not know. We know nothing whatever of such laws and forces, and we gain nothing by veiling our ignorance under a philosophical necessity.

Moreover, if spontaneous generation occurs as a resultant of

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any forces, like forces would produce it again. We have never known it to occur. Should it occur the organisms thus produced would have no bonds of blood-relationship with those already in existence. With these they should show no homology, as they could have no inheritance in common. But all known organisms have common homologies. The factors of organic evolution are essentially the same for all. The unity of life amid all its diversity seems to point to origin from a common stock. If not from one stock, the lines of division between one and another are hidden from us. The study of embryology breaks down the time-honored branch lines of vertebrates, articulates, mollusks, and radiates. The groups of animals are more numerous, more complex, and more intertangled than Cuvier and Agassiz thought. The number of primary branches of animals or plants is uncertain, their boundaries undefined.

If spontaneous generation exists, it is a factor in evolution. If it is a factor, our explanation of the meaning and nature of homology must be fundamentally changed. But it may be that it should be changed. We cannot show that spontaneous generation does not exist. All we know is that we have no means of recognizing it. If there is now spontaneous generation of protoplasm, it cannot take the form of any creature we know. An organism fresh from the mint of creation would be too small for us to see with any microscope. It would be too simple for us to trace by any instrumentality now in our possession. It could contain but a few molecules, and a molecule in a drop of water is as small as an orange beside the sun. Our race of creatures, spontaneously generated, without concessions to environment, would grow hoary with the centuries before it came to our notice. Its descendants would have belonged for ages to the unnumbered hosts of microbes before we should be aware of its creation.

Evolution is not a creed or a body of doctrine to be believed on authority. There is no saving grace in being an evolutionist. There are many who take this name and have no interest in finding out what it means or in making any application of its principles to the affairs of life. For one who cares not to master its ideas, there is no power in the word. Evolution is not a panacea or a medicine to be applied to social or personal ills.

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It is simply an expression of the teaching of enlightened common sense as to the order of changes in life. If its principles are mastered a knowledge of evolution is an aid in the conduct of life, as knowledge of gravitation is essential in the building of machinery.

There is nothing "occult" in the science of evolution. It is not the product of philosophic meditation or of speculative philosophy. It is based on hard facts, and with hard facts it must deal.

It seems to me that it is not true that "Evolution is a new religion, the religion of the future." There are many definitions to religion, but evolution does not fit any of them. It is no more a religion than gravitation is. One may imagine that some enthusiastic follower of Newton may, for the first time, have seen the majestic order of the solar system, may have felt how futile was the old notion of guiding angels, one for each planet to hold it up in space. He may have received his first clear vision of the simple relations of the planets, each forever falling toward the sun and toward each other, each one by the same force forever preserved from collision. Such a man might have exclaimed, "Great is gravitation; it is the new religion, the religion of the future!" In such manner, men trained in dead traditions, once brought to a clear insight of the noble simplicity and adequacy of the theory of evolution, may have exclaimed, "Great is evolution; it is the new religion, the religion of the future!"

But evolution is religion in the same sense that every truth of the physical universe must be religion. That which is true is the truest thing in the world, and the recognition of the infinite soundness at the heart of the universe is an inseparable part of any worthy religion.

But, whether religion or not, the truths of evolution must be their own witness. They can be neither strengthened nor controverted by any authority which may speak in the name of philosophy or of theology or of religion. "Roma locuta est; causa finita est" is not a dictum which science can regard. Her causes are never finished. No power on earth can give beforehand the answer to her questions. Her only court of appeal is the experience of man.