Chapter VII: The Sources of the Principle of Energy (2)

If we look at the matter in this unbiassed light it will appear indubitable that the method of physiological psychology is none other than that of physics; what is more, that this science is a part of physics. Its subject-matter is not different from that of physics. It will unquestionably determine the relations the sensations bear to the physics of our body. We have already learned from a member of this academy (Hering) that in all probability a sixfold manifoldness of the chemical processes of the visual substance corresponds to the sixfold manifoldness of color-sensation, and a threefold manifoldness of the physiological processes to the threefold manifoldness of space-sensations. The paths of reflex actions and of the will are followed up and disclosed; it is ascertained what region of the brain subserves the function of speech, what region the function of locomotion, etc. That which still clings to our body, namely, our thoughts, will, when those investigations are finished, present no difficulties new in principle. When experience has once clearly exhibited these facts and science has marshalled them in economic and perspicuous order, there is no doubt that we shall _understand_ them. For other "understanding" than a mental mastery of facts never existed. Science does not create facts from facts, but simply _orders_ known facts.

Let us look, now, a little more closely into the modes of research of physiological psychology. We have a very clear idea of how a body moves in the space encompassing it. With our optical field of sight we are very familiar. But we are unable to state, as a rule, how we have come by an idea, from what corner of our intellectual field of sight it has entered, or by what region the impulse to a motion is sent forth. Moreover, we shall never get acquainted with this mental field of view from self-observation alone. Self-observation, in conjunction with physiological research, which seeks out physical connexions, can put this field of vision in a clear light before us, and will thus first really reveal to us our inner man.

Primarily, natural science, or physics, in its widest sense, makes us acquainted with only the firmest connexions of groups of elements. Provisorily, we may not bestow too much attention on the single constituents of those groups, if we are desirous of retaining a comprehensible whole. Instead of equations between the primitive variables, physics gives us, as much the easiest course, equations between _functions_ of those variables. Physiological psychology teaches us how to separate the visible, the tangible, and the audible from bodies--a labor which is subsequently richly requited, as the division of the subjects of physics well shows. Physiology further analyses the visible into light and space sensations; the first into colors, the last also into their component parts; it resolves noises into sounds, these into tones, and so on. Unquestionably this analysis can be carried much further than it has been. It will be possible in the end to exhibit the common elements at the basis of very abstract but definite logical acts of like form,--elements which the acute jurist and mathematician, as it were, _feels_ out, with absolute certainty, where the uninitiated hears only empty words. Physiology, in a word, will reveal to us the true real elements of the world. Physiological psychology bears to physics in its widest sense a relation similar to that which chemistry bears to physics in its narrowest sense. But far greater than the mutual support of physics and chemistry will be that which natural science and psychology will render each other. And the results that shall spring from this union will, in all likelihood, far outstrip those of the modern mechanical physics.

What those ideas are with which we shall comprehend the world when the closed circuit of physical and psychological facts shall lie complete before us, (that circuit of which we now see only two disjoined parts,) cannot be foreseen at the outset of the work. The men will be found who will see what is right and will have the courage, instead of wandering in the intricate paths of logical and historical accident, to enter on the straight ways to the heights from which the mighty stream of facts can be surveyed. Whether the notion which we now call matter will continue to have a scientific significance beyond the crude purposes of common life, we do not know. But we certainly shall wonder how colors and tones which were such innermost parts of us could suddenly get lost in our physical world of atoms; how we could be suddenly surprised that something which outside us simply clicked and beat, in our heads should make light and music; and how we could ask whether matter can feel, that is to say, whether a mental symbol for a group of sensations can feel?

We cannot mark out in hard and fast lines the science of the future, but we can foresee that the rigid walls which now divide man from the world will gradually disappear; that human beings will not only confront each other, but also the entire organic and so-called lifeless world, with less selfishness and with livelier sympathy. Just such a presentiment as this perhaps possessed the great Chinese philosopher Licius some two thousand years ago when, pointing to a heap of mouldering human bones, he said to his scholars in the rigid, lapidary style of his tongue: "These and I alone have the knowledge that we neither live nor are dead."

FOOTNOTES:

[Footnote 60: An address delivered before the anniversary meeting of
the Imperial Academy of Sciences, at Vienna, May 25, 1882.]

[Footnote 61: _Primitive Culture._]

[Footnote 62: Tylor, _loc. cit._]

[Footnote 63: _Essai philosophique sur les probabilités_. 6th Ed.
Paris, 1840, p. 4. The necessary consideration of the initial
velocities is lacking in this formulation.]

[Footnote 64: _Principien der Wirthschaftslehre_, Vienna, 1873.]

[Footnote 65: It is clear from this that all so-called elementary
(differential) laws involve a relation to the whole.]

[Footnote 66: If it be objected, that in the case of perturbations
of the velocity of rotation of the earth, we could be sensible of
such perturbations, and being obliged to have some measure of time,
we should resort to the period of vibration of the waves of sodium
light,--all that this would show is that for practical reasons we
should select that event which best served us as the _simplest_
common measure of the others.]

[Footnote 67: Measurement, in fact, is the definition of one
phenomenon by another (standard) phenomenon.]

[Footnote 68: I have represented the point of view here taken for
more than thirty years and developed it in various writings
(_Erhaltung der Arbeit_, 1872, parts of which are published in the
article on _The Conservation of Energy_ in this collection; _The
Forms of Liquids_, 1872, also published in this collection; and the
_Bewegungsempfindungen_, 1875). The idea, though known to
philosophers, is unfamiliar to the majority of physicists. It is a
matter of deep regret to me, therefore, that the title and author of
a small tract which accorded with my views in numerous details and
which I remember having caught a glance of in a very busy period
(1879-1880), have so completely disappeared from my memory that all
efforts to obtain a clue to them have hitherto been fruitless.]

ON TRANSFORMATION AND ADAPTATION IN SCIENTIFIC THOUGHT.[69]

It was towards the close of the sixteenth century that Galileo with a superb indifference to the dialectic arts and sophistic subtleties of the Schoolmen of his time, turned the attention of his brilliant mind to nature. By nature his ideas were transformed and released from the fetters of inherited prejudice. At once the mighty revolution was felt, that was therewith effected in the realm of human thought--felt indeed in circles far remote and wholly unrelated to the sphere of science, felt in strata of society that hitherto had only indirectly recognised the influence of scientific thought.

And how great and how far-reaching that revolution was! From the beginning of the seventeenth century till its close we see arising, at least in embryo, almost all that plays a part in the natural and technical science of to-day, almost all that in the two centuries following so wonderfully transformed the facial appearance of the earth, and all that is moving onward in process of such mighty evolution to-day. And all this, the direct result of Galilean ideas, the direct outcome of that freshly awakened sense for the investigation of natural phenomena which taught the Tuscan philosopher to form the concept and the law of falling bodies from the _observation_ of a falling stone! Galileo began his investigations without an implement worthy of the name; he measured time in the most primitive way, by the efflux of water. Yet soon afterwards the telescope, the microscope, the barometer, the thermometer, the air-pump, the steam engine, the pendulum, and the electrical machine were invented in rapid succession. The fundamental theorems of dynamical science, of optics, of heat, and of electricity were all disclosed in the century that followed Galileo.

Of scarcely less importance, it seems, was that movement which was 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.

* * * * *

Ideas are not all of life. They are only momentary efflorescences of light, designed to illuminate the paths of the will. But as delicate reagents on our organic evolution our ideas are of paramount importance. No theory can gainsay the vital transformation which we feel taking place within us through their agency. Nor is it necessary that we should have a proof of this process. We are immediately assured of it.

The transformation of ideas thus appears as a part of the general evolution of life, as a part of its adaptation to a constantly widening sphere of action. A granite boulder on a mountain-side tends towards the earth below. It must abide in its resting-place for thousands of years before its support gives way. The shrub that grows at its base is farther advanced; it accommodates itself to summer and winter. The fox which, overcoming the force of gravity, creeps to the summit where he has scented his prey, is freer in his movements than either. The arm of man reaches further still; and scarcely anything of note happens in Africa or Asia that does not leave an imprint upon his life. What an immense portion of the life of other men is reflected in ourselves; their joys, their affections, their happiness and misery! And this too, when we survey only our immediate surroundings, and confine our attention to modern literature. How much more do we experience when we travel through ancient Egypt with Herodotus, when we stroll through the streets of Pompeii, when we carry ourselves back to the gloomy period of the crusades or to the golden age of Italian art, now making the acquaintance of a physician of Molière, and now that of a Diderot or of a D'Alembert. What a great part of the life of others, of their character and their purpose, do we not absorb through poetry and music! And although they only gently touch the chords of our emotions, like the memory of youth softly breathing upon the spirit of an aged man, we have nevertheless lived them over again in part. How great and comprehensive does self become in this conception; and how insignificant the person! Egoistical systems both of optimism and pessimism perish with their narrow standard of the import of intellectual life. We feel that the real pearls of life lie in the ever changing contents of consciousness, and that the person is merely an indifferent symbolical thread on which they are strung.[78]

We are prepared, thus, to regard ourselves and every one of our ideas as a product and a subject of universal evolution; and in this way we shall advance sturdily and unimpeded along the paths which the future will throw open to us.[79]

FOOTNOTES:

[Footnote 69: Inaugural Address, delivered on assuming the Rectorate
of the University of Prague, October 18, 1883.

The idea presented in this essay is neither new nor remote. I have
touched upon it myself on several occasions (first in 1867), but
have never made it the subject of a formal disquisition. Doubtless,
others, too, have treated it; it lies, so to speak, in the air.
However, as many of my illustrations were well received, although
known only in an imperfect form from the lecture itself and the
newspapers, I have, contrary to my original intention, decided to
publish it. It is not my intention to trespass here upon the domain
of biology. My statements are to be taken merely as the expression
of the fact that no one can escape the influence of a great and
far-reaching idea.]

[Footnote 70: At first sight an apparent contradiction arises from
the admission of both heredity and adaptation; and it is undoubtedly
true that a strong disposition to heredity precludes great
capability of adaptation. But imagine the organism to be a plastic
mass which retains the form transmitted to it by former influences
until new influences modify it; the _one_ property of _plasticity_
will then represent capability of adaptation as well as power of
heredity. Analogous to this is the case of a bar of magnetised steel
of high coercive force: the steel retains its magnetic properties
until a new force displaces them. Take also a body in motion: the
body retains the velocity acquired in (_inherited_ from) the
interval of time just preceding, except it be changed in the next
moment by an accelerating force. In the case of the body in motion
the _change_ of velocity (_Abänderung_) was looked upon as a matter
of course, while the discovery of the principle of _inertia_ (or
persistence) created surprise; in Darwin's case, on the contrary,
_heredity_ (or persistence) was taken for granted, while the
principle of _variation_ (_Abänderung_) appeared novel.

Fully adequate views are, of course, to be reached only by a study
of the original facts emphasised by Darwin, and not by these
analogies. The example referring to motion, if I am not mistaken, I
first heard, in conversation, from my friend J. Popper, Esq., of
Vienna.

Many inquirers look upon the stability of the species as something
settled, and oppose to it the Darwinian theory. But the stability of
the species is itself a "theory." The essential modifications which
Darwin's views also are undergoing will be seen from the works of
Wallace [and Weismann], but more especially from a book of W. H.
Rolph, _Biologische Probleme_, Leipsic, 1882. Unfortunately, this
last talented investigator is no longer numbered among the living.]

[Footnote 71: Written in 1883.]

[Footnote 72: See Pfaundler, _Pogg. Ann., Jubelband_, p. 182.]

[Footnote 73: See the beautiful discussions of this point in
Hering's _Memory as a General Function of Organised Matter_ (1870),
Chicago, The Open Court Publishing Co., 1887. Compare also Dubois,
_Ueber die Uebung_, Berlin, 1881.]

[Footnote 74: Spencer, _The Principles of Psychology_. London,
1872.]

[Footnote 75: See the article _The Velocity of Light_, page 63.]

[Footnote 76: I am well aware that the endeavor to confine oneself
in natural research to _facts_ is often censured as an exaggerated
fear of metaphysical spooks. But I would observe, that, judged by
the mischief which they have wrought, the metaphysical, of all
spooks, are the least fabulous. It is not to be denied that many
forms of thought were not originally acquired by the individual, but
were antecedently formed, or rather prepared for, in the development
of the species, in some such way as Spencer, Haeckel, Hering, and
others have supposed, and as I myself have hinted on various
occasions.]

[Footnote 77: Compare, for example, _Schiller, Zerstreute
Betrachtungen über verschiedene ästhetische Gegenstände_.]

[Footnote 78: We must not be deceived in imagining that the
happiness of other people is not a very considerable and essential
portion of our own. It is common capital, which cannot be created by
the individual, and which does not perish with him. The formal and
material limitation of the _ego_ is necessary and sufficient only
for the crudest practical objects, and cannot subsist in a broad
conception. Humanity in its entirety may be likened to a
polyp-plant. The material and organic bonds of individual union
have, indeed, been severed; they would only have impeded freedom of
movement and evolution. But the ultimate aim, the psychical
connexion of the whole, has been attained in a much higher degree
through the richer development thus made possible.]

[Footnote 79: C. E. von Baer, the subsequent opponent of Darwin and
Haeckel, has discussed in two beautiful addresses (_Das allgemeinste
Gesetz der Natur in aller Entwickelung_, and _Welche Auffassung der
lebenden Natur ist die richtige, und wie ist diese Auffassung auf
die Entomologie anzuwenden_?) the narrowness of the view which
regards an animal in its existing state as finished and complete,
instead of conceiving it as a phase in the series of evolutionary
forms and regarding the species itself as a phase of the development
of the animal world in general.]

ON THE PRINCIPLE OF COMPARISON IN PHYSICS.[80]

Twenty years ago when Kirchhoff defined the object of mechanics as the "description, in complete and very simple terms, of the motions occurring in nature," he produced by the statement a peculiar impression. Fourteen years subsequently, Boltzmann, in the life-like picture which he drew of the great inquirer, could still speak of the universal astonishment at this novel method of treating mechanics, and we meet with epistemological treatises to-day, which plainly show how difficult is the acceptance of this point of view. A modest and small band of inquirers there were, however, to whom Kirchhoff's few words were tidings of a welcome and powerful ally in the epistemological field.

Now, how does it happen that we yield our assent so reluctantly to the philosophical opinion of an inquirer for whose scientific achievements we have only words of praise? One reason probably is that few inquirers can find time and leisure, amid the exacting employments demanded for the acquisition of new knowledge, to inquire closely into that tremendous psychical process by which science is formed. Further, it is inevitable that much should be put into Kirchhoff's rigid words that they were not originally intended to convey, and that much should be found wanting in them that had always been regarded as an essential element of scientific knowledge. What can mere description accomplish? What has become of explanation, of our insight into the causal connexion of things?

* * * * *

Permit me, for a moment, to contemplate not the results of science, but the mode of its _growth_, in a frank and unbiassed manner. We know of only _one_ source of _immediate revelation_ of scientific facts--_our senses_. Restricted to this source alone, thrown wholly upon his own resources, obliged to start always anew, what could the isolated individual accomplish? Of a stock of knowledge so acquired the science of a distant negro hamlet in darkest Africa could hardly give us a sufficiently humiliating conception. For there that veritable miracle of thought-transference has already begun its work, compared with which the miracles of the spiritualists are rank monstrosities--_communication by language_. Reflect, too, that by means of the magical characters which our libraries contain we can raise the spirits of the "the sovereign dead of old" from Faraday to Galileo and Archimedes, through ages of time--spirits who do not dismiss us with ambiguous and derisive oracles, but tell us the best they know; then shall we feel what a stupendous and indispensable factor in the formation of science _communication_ is. Not the dim, half-conscious _surmises_ of the acute observer of nature or critic of humanity belong to science, but only that which they possess clearly enough to _communicate_ to others.

But how, now, do we go about this communication of a newly acquired experience, of a newly observed fact? As the different calls and battle-cries of gregarious animals are unconsciously formed signs for a common observation or action, irrespective of the causes which produce such action--a fact that already involves the germ of the concept; so also the words of human language, which is only more highly specialised, are names or signs for universally known facts, which all can observe or have observed. If the mental representation, accordingly, follows the new fact at once and _passively_, then that new fact must, of itself, immediately be constituted and represented in thought by facts already universally known and commonly observed. Memory is always ready to put forward for _comparison_ known facts which resemble the new event, or agree with it in certain features, and so renders possible that elementary internal judgment which the mature and definitively formulated judgment soon follows.

Comparison, as the fundamental condition of communication, is the most powerful inner vital element of science. The zoölogist sees in the bones of the wing-membranes of bats, fingers; he compares the bones of the cranium with the vertebræ, the embryos of different organisms with one another, and the different stages of development of the same organism with one another. The geographer sees in Lake Garda a fjord, in the Sea of Aral a lake in process of drying up. The philologist compares different languages with one another, and the formations of the same language as well. If it is not customary to speak of comparative physics in the same sense that we speak of comparative anatomy, the reason is that in a science of such great experimental activity the attention is turned away too much from the _contemplative_ element. But like all other sciences, physics lives and grows by comparison.

* * * * *

The manner in which the result of the comparison finds expression in the communication, varies of course very much. When we say that the colors of the spectrum are red, yellow, green, blue, and violet, the designations employed may possibly have been derived from the technology of tattooing, or they may subsequently have acquired the significance of standing for the colors of the rose, the lemon, the leaf, the corn-flower, and the violet. From the frequent repetition of such comparisons, however, made under the most manifold circumstances, the inconstant features, as compared with the permanent congruent features, get so obliterated that the latter acquire a fixed significance independent of every object and connexion, or take on as we say an _abstract_ or _conceptual_ import. No one thinks at the word "red" of any other agreement with the rose than that of color, or at the word "straight" of any other property of a stretched cord than the sameness of direction. Just so, too, numbers, originally the names of the fingers of the hands and feet, from being used as arrangement-signs for all kinds of objects, were lifted to the plane of abstract concepts. A verbal report (communication) of a fact that uses only these purely abstract implements, we call a _direct description_.

The direct description of a fact of any great extent is an irksome task, even where the requisite notions are already completely developed. What a simplification it involves if we can say, the fact _A_ now considered comports itself, not in _one_, but in _many_ or in _all_ its features, like an old and well-known fact _B_. The moon comports itself as a heavy body does with respect to the earth; light like a wave-motion or an electric vibration; a magnet, as if it were laden with gravitating fluids, and so on. We call such a description, in which we appeal, as it were, to a description already and elsewhere formulated, or perhaps still to be precisely formulated, an _indirect description_. We are at liberty to supplement this description, gradually, by direct description, to correct it, or to replace it altogether. We see, thus, without difficulty, that what is called a _theory_ or a _theoretical idea_, falls under the category of what is here termed indirect description.

* * * * *

What, now, is a theoretical idea? Whence do we get it? What does it accomplish for us? Why does it occupy a higher place in our judgment than the mere holding fast to a fact or an observation? Here, too, memory and comparison alone are in play. But instead of _a single_ feature of resemblance culled from memory, in this case _a great system_ of resemblances confronts us, a well-known physiognomy, by means of which the new fact is immediately transformed into an old acquaintance. Besides, it is in the power of the idea to offer us more than we actually see in the new fact, at the first moment; it can extend the fact, and enrich it with features which we are first induced to _seek_ from such suggestions, and which are often actually found. It is this _rapidity_ in extending knowledge that gives to theory a preference over simple observation. But that preference is wholly _quantitative_. Qualitatively, and in real essential points, theory differs from observation neither in the mode of its origin nor in its last results.

The adoption of a theory, however, always involves a danger. For a theory puts in the place of a fact _A_ in thought, always a _different_, but simpler and more familiar fact _B_, which in _some_ relations can mentally represent _A_, but for the very reason that it is different, in other relations cannot represent it. If now, as may readily happen, sufficient care is not exercised, the most fruitful theory may, in special circumstances, become a downright obstacle to inquiry. Thus, the emission-theory of light, in accustoming the physicist to think of the projectile path of the "light-particles" as an undifferentiated straight-line, demonstrably impeded the discovery of the periodicity of light. By putting in the place of light the more familiar phenomena of sound, Huygens renders light in many of its features a familiar event, but with respect to polarisation, which lacks the longitudinal waves with which alone he was acquainted, it had for him a doubly strange aspect. He is unable thus to grasp in abstract thought the fact of polarisation, which is before his eyes, whilst Newton, merely by adapting to the observation his thoughts, and putting this question, "_Annon radiorum luminis diversa sunt latera?_" abstractly grasped polarisation, that is, directly described it, a century before Malus. On the other hand, if the agreement of the fact with the idea theoretically representing it, extends further than its inventor originally anticipated, then we may be led by it to unexpected discoveries, of which conical refraction, circular polarisation by total reflexion, Hertz's waves offer ready examples, in contrast to the illustrations given above.

Our insight into the conditions indicated will be improved, perhaps, by contemplating the development of some theory or other more in detail. Let us consider a magnetised bar of steel by the side of a second unmagnetised bar, in all other respects the same. The second bar gives no indication of the presence of iron-filings; the first attracts them. Also, when the iron-filings are absent, we must think of the magnetised bar as in a different condition from that of the unmagnetised. For, that the mere presence of the iron-filings does not induce the phenomenon of attraction is proved by the second unmagnetised bar. The ingenuous man, who finds in his will, as his most familiar source of power, the best facilities for comparison, conceives a species of _spirit_ in the magnet. The behavior of a warm body or of an _electrified_ body suggests similar ideas. This is the point of view of the oldest theory, _fetishism_, which the inquirers of the early Middle Ages had not yet overcome, and which in its last vestiges, in the conception of forces, still flourishes in modern physics. We see, thus, the _dramatic_ element need no more be absent in a scientific description, than in a thrilling novel.

If, on subsequent examination, it be observed that a cold body, in contact with a hot body, warms itself, so to speak, _at the expense_ of the hot body; further, that when the substances are the same, the cold body, which, let us say, has twice the mass of the other, gains only half the number of degrees of temperature that the other loses, a wholly new impression arises. The demoniac character of the event vanishes, for the supposed spirit acts not by caprice, but according to fixed laws. In its place, however, _instinctively_ the notion of a _substance_ is substituted, part of which flows over from the one body to the other, but the total amount of which, representable by the sum of the products of the masses into the respective changes of temperature, remains constant. Black was the first to be _powerfully_ struck with this resemblance of thermal processes to the motion of a substance, and under its guidance discovered the specific heat, the heat of fusion, and the heat of vaporisation of bodies. Gaining strength and fixity, however, from these successes, this notion of substance subsequently stood in the way of scientific advancement. It blinded the eyes of the successors of Black, and prevented them from seeing the manifest fact, which every savage knows, that heat is _produced_ by friction. Fruitful as that notion was for Black, helpful as it still is to the learner to-day in Black's special field, permanent and universal validity as a _theory_ it could never maintain. But what is essential, conceptually, in it, viz., the constancy of the product-sum above mentioned, retains its value and may be regarded as a _direct description_ of Black's facts.