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 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 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 evolution 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 (βιος, life; υομος, 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 limitations, 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