prepared for by the illustrious biologists of the hundred years just
past, and formally begun by the late Mr. Darwin. Galileo quickened the
sense for the simpler phenomena of _inorganic_ nature. And with the same
simplicity and frankness that marked the efforts of Galileo, and without
the aid of technical or scientific instruments, without physical or
chemical experiment, but solely by the power of thought and observation,
Darwin grasps a new property of _organic_ nature--which we may briefly
call its _plasticity_.[70] With the same directness of purpose, Darwin,
too, pursues his way. With the same candor and love of truth, he points
out the strength and the weakness of his demonstrations. With masterly
equanimity he holds aloof from the discussion of irrelevant subjects and
wins alike the admiration of his adherents and of his adversaries.
Scarcely thirty years have elapsed[71] since Darwin first propounded the
principles of his theory of evolution. Yet, already we see his ideas
firmly rooted in every branch of human thought, however remote.
Everywhere, in history, in philosophy, even in the physical sciences, we
hear the watchwords: heredity, adaptation, selection. We speak of the
struggle for existence among the heavenly bodies and of the struggle for
existence in the world of molecules.[72]
The impetus given by Galileo to scientific thought was marked in every
direction; thus, his pupil, Borelli, founded the school of exact
medicine, from whence proceeded even distinguished mathematicians. And
now Darwinian ideas, in the same way, are animating all provinces of
research. It is true, nature is not made up of two distinct parts, the
inorganic and the organic; nor must these two divisions be treated
perforce by totally distinct methods. Many _sides_, however, nature has.
Nature is like a thread in an intricate tangle, which must be followed
and traced, now from this point, now from that. But we must never
imagine,--and this physicists have learned from Faraday and J. R.
Mayer,--that progress along paths once entered upon is the _only_ means
of reaching the truth.
It will devolve upon the specialists of the future to determine the
relative tenability and fruitfulness of the Darwinian ideas in the
different provinces. Here I wish simply to consider the growth of
natural _knowledge_ in the light of the theory of evolution. For
knowledge, too, is a product of organic nature. And although ideas, as
such, do not comport themselves in all respects like independent organic
individuals, and although violent comparisons should be avoided, still,
if Darwin reasoned rightly, the general imprint of evolution and
transformation must be noticeable in ideas also.
I shall waive here the consideration of the fruitful topic of the
transmission of ideas or rather of the transmission of the aptitude for
certain ideas.[73] Nor would it come within my province to discuss
psychical evolution in any form, as Spencer[74] and many other modern
psychologists have done, with varying success. Neither shall I enter
upon a discussion of the struggle for existence and of natural selection
among scientific theories.[75] We shall consider here only such
processes of transformation as every student can easily observe in his
own mind.
* * * * *
The child of the forest picks out and pursues with marvellous acuteness
the trails of animals. He outwits and overreaches his foes with
surpassing cunning. He is perfectly at home in the sphere of his
peculiar experience. But confront him with an unwonted phenomenon; place
him face to face with a technical product of modern civilisation, and he
will lapse into impotency and helplessness. Here are facts which he
does not comprehend. If he endeavors to grasp their meaning, he
misinterprets them. He fancies the moon, when eclipsed, to be tormented
by an evil spirit. To his mind a puffing locomotive is a living monster.
The letter accompanying a commission with which he is entrusted, having
once revealed his thievishness, is in his imagination a conscious being,
which he must hide beneath a stone, before venturing to commit a fresh
trespass. Arithmetic to him is like the art of the geomancers in the
Arabian Nights,--an art which is able to accomplish every imaginable
impossibility. And, like Voltaire's _ingénu_, when placed in our social
world, he plays, as we think, the maddest pranks.
With the man who has made the achievements of modern science and
civilisation his own, the case is quite different. He sees the moon pass
temporarily into the shadow of the earth. He feels in his thoughts the
water growing hot in the boiler of the locomotive; he feels also the
increase of the tension which pushes the piston forward. Where he is not
able to trace the direct relation of things he has recourse to his
yard-stick and table of logarithms, which aid and facilitate his thought
without predominating over it. Such opinions as he cannot concur in, are
at least known to him, and he knows how to meet them in argument.
Now, wherein does the difference between these two men consist? The
train of thought habitually employed by the first one does not
correspond to the facts that he sees. He is surprised and nonplussed at
every step. But the thoughts of the second man follow and anticipate
events, his thoughts have become adapted or accommodated to the larger
field of observation and activity in which he is located; he conceives
things as they are. The Indian's sphere of experience, however, is quite
different; his bodily organs of sense are in constant activity; he is
ever intensely alert and on the watch for his foes; or, his entire
attention and energy are engaged in procuring sustenance. Now, how can
such a creature project his mind into futurity, foresee or prophesy?
This is not possible until our fellow-beings have, in a measure,
relieved us of our concern for existence. It is then that we acquire
freedom for observation, and not infrequently too that narrowness of
thought which society helps and teaches us to disregard.
If we move for a time within a fixed circle of phenomena which recur
with unvarying uniformity, our thoughts gradually adapt themselves to
our environment; our ideas reflect unconsciously our surroundings. The
stone we hold in our hand, when dropped, not only falls to the ground in
reality; it also falls in our thoughts. Iron-filings dart towards a
magnet in imagination as well as in fact, and, when thrown into a fire,
they grew hot in conception as well.
The impulse to complete mentally a phenomenon that has been only
partially observed, has not its origin in the phenomenon itself; of this
fact, we are fully sensible. And we well know that it does not lie
within the sphere of our volition. It seems to confront us rather as a
power and a law imposed from without and controlling both thought and
facts.
The fact that we are able by the help of this law to prophesy and
forecast, merely proves a sameness or uniformity of environment
sufficient to effect a mental adaptation of this kind. A necessity of
fulfilment, however, is not contained in this compulsory principle which
controls our thoughts; nor is it in any way determined by the
possibility of prediction. We are always obliged, in fact, to await the
completion of what has been predicted. Errors and departures are
constantly discernible, and are slight only in provinces of great rigid
constancy, as in astronomy.
In cases where our thoughts follow the connexion of events with ease,
and in instances where we positively forefeel the course of a
phenomenon, it is natural to fancy that the latter is determined by and
must conform to our thoughts. But the belief in that mysterious agency
called _causality_, which holds thought and event in unison, is
violently shaken when a person first enters a province of inquiry in
which he has previously had no experience. Take for instance the strange
interaction of electric currents and magnets, or the reciprocal action
of currents, which seem to defy all the resources of mechanical science.
Let him be confronted with such phenomena and he will immediately feel
himself forsaken by his power of prediction; he will bring nothing with
him into this strange field of events but the hope of soon being able
to adapt his ideas to the new conditions there presented.
A person constructs from a bone the remaining anatomy of an animal; or
from the visible part of a half-concealed wing of a butterfly he infers
and reconstructs the part concealed. He does so with a feeling of
highest confidence in the accuracy of his results; and in these
processes we find nothing preternatural or transcendent. But when
physicists adapt their thoughts to conform to the dynamical course of
events in time, we invariably surround their investigations with a
metaphysical halo; yet these latter adaptations bear quite the same
character as the former, and our only reason for investing them with a
metaphysical garb, perhaps, is their high practical value.[76]
Let us consider for a moment what takes place when the field of
observation to which our ideas have been adapted and now conform,
becomes enlarged. We had, let us say, always seen heavy bodies sink when
their support was taken away; we had also seen, perhaps, that the
sinking of heavier bodies forced lighter bodies upwards. But now we see
a lever in action, and we are suddenly struck with the fact that a
lighter body is lifting another of much greater weight. Our customary
train of thought demands its rights; the new and unwonted event likewise
demands its rights. From this conflict between thought and fact the
_problem_ arises; out of this partial contrariety springs the question,
"Why?" With the new adaptation to the enlarged field of observation, the
problem disappears, or, in other words, is solved. In the instance
cited, we must adopt the habit of always considering the mechanical work
performed.
The child just awakening into consciousness of the world, knows no
problem. The bright flower, the ringing bell, are all new to it; yet it
is surprised at nothing. The out and out Philistine, whose only thoughts
lie in the beaten path of his every-day pursuits, likewise has no
problems. Everything goes its wonted course, and if perchance a thing go
wrong at times, it is at most a mere object of curiosity and not worth
serious consideration. In fact, the question "Why?" loses all warrant in
relations where we are familiar with every aspect of events. But the
capable and talented young man has his head full of problems; he has
acquired, to a greater or less degree, certain habitudes of thought, and
at the same time he is constantly observing what is new and unwonted,
and in his case there is no end to the questions, "Why?"
Thus, the factor which most promotes scientific thought is the gradual
widening of the field of experience. We scarcely notice events we are
accustomed to; the latter do not really develop their intellectual
significance until placed in contrast with something to which we are
unaccustomed. Things that at home are passed by unnoticed, delight us
when abroad, though they may appear in only slightly different forms.
The sun shines with heightened radiance, the flowers bloom in brighter
colors, our fellow-men accost us with lighter and happier looks. And,
returning home, we find even the old familiar scenes more inspiring and
suggestive than before.
Every motive that prompts and stimulates us to modify and transform our
thoughts, proceeds from what is new, uncommon, and not understood.
Novelty excites wonder in persons whose fixed habits of thought are
shaken and disarranged by what they see. But the element of wonder never
lies in the phenomenon or event observed; its place is in the person
observing. People of more vigorous mental type aim at once at an
_adaptation of thought_ that will conform to what they have observed.
Thus does science eventually become the natural foe of the wonderful.
The sources of the marvellous are unveiled, and surprise gives way to
calm interpretation.
Let us consider such a mental transformative process in detail. The
circumstance that heavy bodies fall to the earth appears perfectly
natural and regular. But when a person observes that wood floats upon
water, and that flames and smoke rise in the air, then the contrary of
the first phenomenon is presented. An olden theory endeavors to explain
these facts by imputing to substances the power of volition, as that
attribute which is most familiar to man. It asserted that every
substance seeks its proper place, heavy bodies tending downwards and
light ones upwards. It soon turned out, however, that even smoke had
weight, that it, too, sought its place below, and that it was forced
upwards only because of the downward tendency of the air, as wood is
forced to the surface of water because the water exerts the greater
downward pressure.
Again, we see a body thrown into the air. It ascends. How is it that it
does not seek its proper place? Why does the velocity of its "violent"
motion decrease as it rises, while that of its "natural" fall increases
as it descends. If we mark closely the relation between these two facts,
the problem will solve itself. We shall see, as Galileo did, that the
decrease of velocity in rising and the increase of velocity in falling
are one and the same phenomenon, viz., an increase of velocity towards
the earth. Accordingly, it is not a place that is assigned to the body,
but an increase of velocity towards the earth.
By this idea the movements of heavy bodies are rendered perfectly
familiar. Newton, now, firmly grasping this new way of thinking, sees
the moon and the planets moving in their paths upon principles similar
to those which determine the motion of a projectile thrown into the air.
Yet the movements of the planets were marked by peculiarities which
compelled him once more to modify slightly his customary mode of
thought. The heavenly bodies, or rather the parts composing them, do not
move with constant accelerations towards each other, but "attract each
other," directly as the mass and inversely as the square of the
distance.
This latter notion, which includes the one applying to terrestrial
bodies as a special case, is, as we see, quite different from the
conception from which we started. How limited in scope was the original
idea and to what a multitude of phenomena is not the present one
applicable! Yet there is a trace, after all, of the "search for place"
in the expression "attraction." And it would be folly, indeed, for us to
avoid, with punctilious dread, this conception of "attraction" as
bearing marks of its pedigree. It is the historical base of the
Newtonian conception and it still continues to direct our thoughts in
the paths so long familiar to us. Thus, the happiest ideas do not fall
from heaven, but spring from notions already existing.
Similarly, a ray of light was first regarded as a continuous and
homogeneous straight line. It then became the path of projection for
minute missiles; then an aggregate of the paths of countless different
kinds of missiles. It became periodic; it acquired various sides; and
ultimately it even lost its motion in a straight line.
The electric current was conceived originally as the flow of a
hypothetical fluid. To this conception was soon added the notion of a
chemical current, the notion of an electric, magnetic, and anisotropic
optical field, intimately connected with the path of the current. And
the richer a conception becomes in following and keeping pace with
facts, the better adapted it is to anticipate them.
Adaptive processes of this kind have no assignable beginning, inasmuch
as every problem that incites to new adaptation, presupposes a fixed
habitude of thought. Moreover, they have no visible end; in so far as
experience never ceases. Science, accordingly, stands midway in the
evolutionary process; and science may advantageously direct and promote
this process, but it can never take its place. That science is
inconceivable the principles of which would enable a person with no
experience to construct the world of experience, without a knowledge of
it. One might just as well expect to become a great musician, solely by
the aid of theory, and without musical experience; or to become a
painter by following the directions of a text-book.
In glancing over the history of an idea with which we have become
perfectly familiar, we are no longer able to appreciate the full
significance of its growth. The deep and vital changes that have been
effected in the course of its evolution, are recognisable only from the
astounding narrowness of view with which great contemporary scientists
have occasionally opposed each other. Huygens's wave-theory of light was
incomprehensible to Newton, and Newton's idea of universal gravity was
unintelligible to Huygens. But a century afterwards both notions were
reconcilable, even in ordinary minds.
On the other hand, the original creations of pioneer intellects,
unconsciously formed, do not assume a foreign garb; their form is their
own. In them, childlike simplicity is joined to the maturity of manhood,
and they are not to be compared with processes of thought in the average
mind. The latter are carried on as are the acts of persons in the state
of mesmerism, where actions involuntarily follow the images which the
words of other persons suggest to their minds.
The ideas that have become most familiar through long experience, are
the very ones that intrude themselves into the conception of every new
fact observed. In every instance, thus, they become involved in a
struggle for self-preservation, and it is just they that are seized by
the inevitable process of transformation.
Upon this process rests substantially the method of explaining by
hypothesis new and uncomprehended phenomena. Thus, instead of forming
entirely new notions to explain the movements of the heavenly bodies and
the phenomena of the tides, we imagine the material particles composing
the bodies of the universe to possess weight or gravity with respect to
one another. Similarly, we imagine electrified bodies to be freighted
with fluids that attract and repel, or we conceive the space between
them to be in a state of elastic tension. In so doing, we substitute
for new ideas distinct and more familiar notions of old
experience--notions which to a great extent run unimpeded in their
courses, although they too must suffer partial transformation.
The animal cannot construct new members to perform every new function
that circumstances and fate demand of it. On the contrary it is obliged
to make use of those it already possesses. When a vertebrate animal
chances into an environment where it must learn to fly or swim, an
additional pair of extremities is not grown for the purpose. On the
contrary, the animal must adapt and transform a pair that it already
has.
The construction of hypotheses, therefore, is not the product of
artificial scientific methods. This process is unconsciously carried on
in the very infancy of science. Even later, hypotheses do not become
detrimental and dangerous to progress except when more reliance is
placed on them than on the facts themselves; when the contents of the
former are more highly valued than the latter, and when, rigidly
adhering to hypothetical notions, we overestimate the ideas we possess
as compared with those we have to acquire.
The extension of our sphere of experience always involves a
transformation of our ideas. It matters not whether the face of nature
becomes actually altered, presenting new and strange phenomena, or
whether these phenomena are brought to light by an intentional or
accidental turn of observation. In fact, all the varied methods of
scientific inquiry and of purposive mental adaptation enumerated by John
Stuart Mill, those of observation as well as those of experiment, are
ultimately recognisable as forms of one fundamental method, the method
of change, or variation. It is through change of circumstances that the
natural philosopher learns. This process, however, is by no means
confined to the investigator of nature. The historian, the philosopher,
the jurist, the mathematician, the artist, the æsthetician,[77] all
illuminate and unfold their ideas by producing from the rich treasures
of memory similar, but different, cases; thus, they observe and
experiment in their thoughts. Even if all sense-experience should
suddenly cease, the events of the days past would meet in different
attitudes in the mind and the process of adaptation would still
continue--a process which, in contradistinction to the adaptation of
thoughts to facts in practical spheres, would be strictly theoretical,
being an adaptation of thoughts to thoughts.
The method of change or variation brings before us like cases of
phenomena, having partly the same and partly different elements. It is
only by comparing different cases of refracted light at changing angles
of incidence that the common factor, the constancy of the refractive
index, is disclosed. And only by comparing the refractions of light of
different colors, does the difference, the inequality of the indices of
refraction, arrest the attention. Comparison based upon change leads the
mind simultaneously to the highest abstractions and to the finest
distinctions.
Undoubtedly, the animal also is able to distinguish between the similar
and dissimilar of two cases. Its consciousness is aroused by a noise or
a rustling, and its motor centre is put in readiness. The sight of the
creature causing the disturbance, will, according to its size, provoke
flight or prompt pursuit; and in the latter case, the more exact
distinctions will determine the mode of attack. But man alone attains to
the faculty of voluntary and conscious comparison. Man alone can, by his
power of abstraction, rise, in one moment, to the comprehension of
principles like the conservation of mass or the conservation of energy,
and in the next observe and mark the arrangement of the iron lines in
the spectrum. In thus dealing with the objects of his conceptual life,
his ideas unfold and expand, like his nervous system, into a widely
ramified and organically articulated tree, on which he may follow every
limb to its farthermost branches, and, when occasion demands, return to
the trunk from which he started.
The English philosopher Whewell has remarked that two things are
requisite to the formation of science: facts and ideas. Ideas alone lead
to empty speculation; mere facts can yield no organic knowledge. We see
that all depends upon the capacity of adapting existing notions to fresh
facts.
Over-readiness to yield to every new fact prevents fixed habits of
thought from arising. Excessively rigid habits of thought impede freedom
of observation. In the struggle, in the compromise between judgment and
prejudgment (prejudice), if we may use the term, our understanding of
things broadens.
Habitual judgment, applied to a new case without antecedent tests, we
call prejudgment or prejudice. Who does not know its terrible power! But
we think less often of the importance and utility of prejudice.
Physically, no one could exist, if he had to guide and regulate the
circulation, respiration, and digestion of his body by conscious and
purposive acts. So, too, no one could exist intellectually if he had to
form judgments on every passing experience, instead of allowing himself
to be controlled by the judgments he has already formed. Prejudice is a
sort of reflex motion in the province of intelligence.
On prejudices, that is, on habitual judgments not tested in every case
to which they are applied, reposes a goodly portion of the thought and
work of the natural scientist. On prejudices reposes most of the conduct
of society. With the sudden disappearance of prejudice society would
hopelessly dissolve. That prince displayed a deep insight into the power
of intellectual habit, who quelled the loud menaces and demands of his
body-guard for arrears of pay and compelled them to turn about and
march, by simply pronouncing the regular word of command; he well knew
that they would be unable to resist that.
Not until the discrepancy between habitual judgments and facts becomes
great is the investigator implicated in appreciable illusion. Then
tragic complications and catastrophes occur in the practical life of
individuals and nations--crises where man, placing custom above life,
instead of pressing it into the service of life, becomes the victim of
his error. The very power which in intellectual life advances, fosters,
and sustains us, may in other circumstances delude and destroy us.
* * * * *