This 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 mere 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 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 ([Greek: bios], life; [Greek:
nomos], 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 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 snow-bank. 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 cannot 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 cast-off
snake-skin." 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. 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 cast-off snake-skin."
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. "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 in 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 to-day 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 to-day 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 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 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 to-morrow, 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.