CHAPTER XXIV

THEORIES HOW REACHED AND USED

Educated guessing . . . Weaving power . . . Imagination indispensable . . . The proving process . . . Theory gainfully directs both observation and experiment . . . Professor Tyndall’s views . . . Discursiveness illustrated in Thomas Young.

Theories as Finder Thoughts.

As far back as the first man with brains in his head, there was an ache to know why the sun shone, the stars twinkled, the winds blew, why harvests here were plentiful and there scant. The whole burden of witchcraft, of fetichism, of beliefs in voodoo, is a pathetic proof of this human longing to explain. What, after all, are superstitions but premature explanations that overstay their time? When men of thought get a glimpse of an interpretation really true, they are eager to prolong that glimpse until it becomes a survey whose due tests confirm and buttress a well grounded anticipation. This exploring process reminds us of what took place long ago when an architect of unexampled boldness first imagined a dome for a temple, and brought his dream to fulfilment. He began by rearing a single arch, fairly strong, yet hardly strong enough; a second arch arose to meet the first at their common crest; now, in mutual support both had a stability neither could display alone; at last when the wall had gone full circle it had a strength vastly greater than that of any part by itself. The long-admired arch had indeed become no more than an element to be joined with other arches to create a unit of an order distinctly higher.

For ages the men who studied nature looked upon it as little changed since it left its Maker’s hand. Of infinite stimulus was the perception that it is a drama, not a tableau, which spreads itself before the eye. Speedily and with incomparable instruction it was traced how every actor in that drama had been molded by the part it had played in maintaining itself upon the stage of life. Every rival, parasite or foe, every stress of climate, was studied in its influence on food or frame, while the ever-threatened doom for irresponsiveness was the extinction which befell countless forms once masters of the earth. No hue of scale or feather, no barb or tusk, no curve of beak or note of song but served a purpose in the plot or advanced the action in some conflict to the death. When Darwin was confronted in plant or beast by an organ or a habit which puzzled him, he was wont to ask, What use can this have had? And seldom was the question asked in vain. He laid great stress on the directive worth of a well-considered theory. He tells us, “I am a firm believer that without speculation there is no good and original observation.” In a letter he remarks, “It is an old and firm conviction of mine that the naturalists who accumulate facts and make many partial generalizations are the _real_ benefactors of science. Those who merely accumulate facts I cannot very much respect.”

In rising from facts to explanations a weighty debt is due to modern aids to eyes and hands. To men who knew only what direct vision could tell them in a single life-time, it was but natural to repeat:--“The thing that hath been, is that which shall be; and that which is done, is that which shall be done; and there is no new thing under the sun.” But we of to-day are in different case. The astronomer, joining camera to telescope, lengthens the diameter of the known universe a thousand-fold; he discovers system after system in stages of life such as our sun and its attendant orbs have passed through in ages so remote as to refuse computation. And many types of nebulae and stars are now studied which were never so much as imagined until they revealed themselves upon the photographic plate. Meanwhile the geologist, examining the closely welded ribs of our globe, comparing the birds, beasts and men of to-day with their earliest known ancestry, believes that the earth has been a scene of life for a million centuries or more. As we restore one act after another in this great cosmical drama, we are able to forecast those which may next appear. Because the whole scheme of things from centre to rim pulses in one ethereal ocean, every actor has interplay with every other, so that the sweep of events discloses a unity all the more intimate the more closely it is studied. At this hour physicists and chemists, with electricity their new servant at command, are gathering proof that what have long been called “elements,” are probably one substance, variously assembled, moving at speeds and in paths infinitely diverse, repeating in little the mighty swings of suns and planets. Throughout these researches a constant spur is the thought that here may be traced such processes of development as have been laid bare in every other province of nature. From circumference to centre, evolution is the master key of each keen questioner.

Modern Views of Matter.

Organic nature to the modern interpreter is thus alive through and through. In his view atom and molecule are also alive in a subordinate, elemental degree. Indeed, he thinks, it is their life borne in air, water and food which in plant or animal rises to new planes of dignity. He looks afresh at the broken alum crystal which repairs itself in a solution, and sees there the removal of the imaginary fence which long divided organic nature from inorganic. (See illustration, page 194.) It was a shrewd guess of Sir Isaac Newton that the diamond is combustible; he did not suspect it to be carbon, but he knew it to be highly refrangible as are many combustible bodies. His conjecture shows him taking the first step toward the current view that properties, the modes of behavior of matter, are not passive qualities, but are due to real activities; that what a substance is depends upon how its ultimate parts move. Clausius and Maxwell in a theory which marks a new era explained the elasticity of gases as manifested in the ceaseless motion of their molecules, declaring that an ounce of air within a fragile jar is able to sustain the pressure of the atmosphere around it, because the air, though only an ounce in weight, dashes against its container with an impact forcible enough to balance the external pressure. Proof whereof appears in measuring the velocity of air as it rushes into a vacuum. Here a significant point is that in leaving the realm of mass-mechanics, where the tax of friction is inexorable, we enter a sphere where the swiftest motion may go on forever without paying friction the smallest levy.

Elasticity Explained.

Elasticity of solids is explained on the same principle. If we swiftly turn a gyroscopic wheel we can only change its plane of rotation by an effort, which effort is repaid when the metal is allowed to resume its original plane of motion. It is imagined that in like manner the particles in an elastic spring move rapidly in a definite plane; if deflected therefrom they oppose resistance and are ready to do work in returning thereto. Of kindred to the kinetic theory of elasticity is the explanation of heat as a distinct and ceaseless molecular motion on which the dimensions of masses depend. It has long seemed to me that every case of “potential” energy, as that of a spring bent or coiled, may in like manner embody actual though impalpable and invisible motion. I presented this view in the Popular Science Monthly, December, 1876.

The very constitution of matter is now referred to the motions, highly diversified, of the simplest substance possible. Helmholtz, Lord Kelvin, and Professor Clerk Maxwell have imagined the molecules of lead, iron, or other element as vortices born of the ether in which without resistance they forever whirl. As we see in the case of a quickly rotated chain, substantial rigidity is conferred by motion sufficiently swift. Nor are molecules without somewhat of individuality. We are wont to think of masses of solid iron as precisely similar in quality, but experience shows us that one bar of iron may vary from another by all that has differenced the history of the two. A careful workman uses a steel die for only a short service before he returns it to the annealer, well assured that the metal, despite its seeming wholeness, has suffered severe internal strain at every blow, which, were no caution exercised, would soon reveal itself in fracture of the die, or ruined work. Facts of this kind, which every day confront the mechanic and engineer, convey a prophecy of the sensibility and memory which dawn with life.

Guesses and Proof.

A theory helpful to the observer or the experimenter comes at last, in many cases, from much guessing. The theorist fills his mind with facts, broods over them, endeavors to explain them, but whether his theory is true or false must be decided solely by proof. This point was clearly stated by Dr. Pye-Smith, of London, in his Harveian oration, 1893:--“As Paley justly puts it, he only discovers who proves. To hit upon a true conjecture here and there, amid a crowd of untrue, and leave it again without appreciation of its importance, is a sign, not of intelligence, but of frivolity. We are told that of the seven wise men of Greece, one (I believe it was Thales) taught that the sun did not go around the earth, but the earth around the sun. Hence it has been said that Thales anticipated Copernicus--a flagrant example of the fallacy in question. A crowd of idle philosophers who sat through the long summer days and nights of Attica discussing all things in heaven and earth must sometimes have hit upon a true opinion, if only by accident, but Thales, or whoever broached the heliocentric dogma, had no reason for his belief and showed himself not more, but less, reasonable than his companions. The crude theories and gross absurdities of phrenology are not in the least justified or even excused by the present knowledge of cerebral localization; nor do the baseless speculations of Lamarck and Erasmus Darwin entitle them to be regarded as the forerunners of Charles Darwin. Up to 1859 impartial and competent men were bound to disbelieve in evolution. After that date, or at least, so soon as the facts and arguments of Darwin and Wallace had been published, they were equally bound to believe in it. He discovers who proves, and by this test Harvey is the sole and absolute discoverer of the movements of the heart and of the blood.”

The Knitting Faculty.

Discovery is the reward of diligence, such as that of Harvey, but not of diligence alone. Professor William James, in his Psychology remarks:--“The inquirer starts with a fact of which he sees the reason, or a theory of which he sees the proof. In either case he keeps turning the matter incessantly in his mind, until by the arousal of associate upon associate, some habitual, some similar, one arises which he recognizes to suit his need. This, however, may take years. No rules can be given by which the investigator can proceed straight to his result; but both here and in the case of reminiscence the accumulation of helps in the way of associations may advance more rapidly by the use of certain methods. In striving to recall a thought, for example, we may of set purpose run through the successive classes of circumstances with which it may possibly have been connected, trusting that when the right member of the class has turned up it will help the thought’s revival. . . . In scientific research this accumulation of associates has been methodized by Mill as ‘four methods of experimental inquiry.’ By the method of Agreement, of Difference, of Residues, and of Concomitant Variations, we make certain lists of cases, and by ruminating these lists in our minds the cause we seek will be more likely to emerge. But the final stroke of discovery is only prepared, not effected by them. The brain tracts must, of their own accord, shoot the right way at last, or we shall still grope in darkness.”

The Detection of Likeness Beneath Diversity.

Among the talents of the discoverer, perhaps the chief is to detect similarity in phenomena which, to casual observation, are unlike. Of this the capital example is Franklin’s proof that lightning and common frictional electricity are one and the same. Professor Alexander Bain, in “The Senses and the Intellect,” thus describes this talent:--“When it first occurred to a reflecting mind that moving water had a property identical with human or brute force, namely, the property of setting other masses in motion, overcoming resistance and inertia--when the sight of the stream suggested through this point of likeness the power of the animal--a new addition was made to the class of prime movers, and when circumstances permitted, this power could be made a substitute for the others. It may seem to the modern understanding, familiar with water-wheels and drifting rafts, that the similarity here was an extremely obvious one. But if we put ourselves back into an early state of mind, when running water affected the mind by its brilliancy, its roar, and irregular devastation, we may easily suppose that to identify this with animal muscular energy was by no means an obvious effect. Doubtless when a mind arose, insensible by natural constitution to the superficial aspects of things, and having withal a great stretch of identifying intellect, such a comparison would then be possible. We may pursue the same example one stage further, and come to the discovery of steam-power, or the identification of expanding vapor with the previously known sources of mechanical force. To the common eye, for ages, vapor presented itself as clouds in the sky; or, as a hissing noise at the spout of a kettle, with the formation of a foggy, curling cloud at a few inches’ distance. The forcing up of the lid of a kettle may also have been occasionally observed. But how long was it ere any one was struck with parallelism of this appearance with a blast of wind, a rush of water, or an exertion of animal muscle? The discordance was too great to be broken through by such a faint and limited amount of likeness. In one mind, however, the identification did take place, and was followed out into its consequences. The likeness had occurred to other minds previously, but not with the same results. Such minds must have been in some way or other distinguished above the millions of mankind, and we are endeavoring to give an explanation of their superiority. The intellectual character of Watt contained all the elements preparatory to a great stroke of similarity in such a case--a high susceptibility, both by nature and education, to the mechanical properties of bodies; ample previous knowledge, or familiarity; and indifference to the superficial and sensational effects of things. It is not only possible, however, but exceedingly probable, that many men possessed all these accomplishments; they are of a kind not transcending common abilities. They would in some degree attach to a mechanical education, as a matter of course. That the discovery was not sooner made supposes that something farther, and not of common occurrence was necessary; and this additional endowment appears to be the identifying power of similarity in general; the tendency to detect likeness in the midst of disparity and disguise. This supposition accounts for the fact, and is consistent with the known intellectual character of the inventor of the steam engine.”

The Part Played by Imagination.

A discoverer needs for success much more than identifying power. Professor John Tyndall, one of the chief expositors of science in the nineteenth century, speaks thus of the part played by an investigator’s imagination:--

“How are the hidden things of nature to be revealed? How, for example, are we to lay hold of the physical basis of light, since, like that of life itself, it lies entirely outside the domain of the senses? Now philosophers may be right in affirming that we cannot transcend experience. But we can, at all events, carry it a long way from its origin. We can also magnify, diminish, qualify, and combine experiences, so as to render them fit for purposes entirely new. We are gifted with the power of Imagination, and by this power we can lighten the darkness which surrounds the world of the senses. There are tories even in science who regard imagination as a faculty to be feared and avoided rather than employed. They had observed its action in weak vessels and were unduly impressed by its disasters. But they might with equal justice point to exploded boilers as an argument against the use of steam. Bounded and conditioned by co-operative reason, imagination becomes the mightiest instrument of the physical discoverer. Newton’s passage from a falling apple to a falling moon was, at the outset, a leap of the imagination. When William Thomson tries to place the ultimate particles of matter between his compass points, and to apply to them a scale of millimeters, he is powerfully aided by this faculty. And in much that has recently been said about protoplasm and life, we have the outgoings of the imagination guided and controlled by the known analogies of science. In fact, without this power, our knowledge of nature would be a mere tabulation of co-existences and sequences. We should still believe in the succession of day and night, of summer and winter; but the soul of Force would be dislodged from our universe; causal relations would disappear, and with them that science which is now binding the parts of nature into an organic whole.”

Professor Tyndall also tells us how sound theories are divided from unsound:--

Theories Must be Verified.

“From a starting-point furnished from his own researches or those of others, the investigator proceeds by combining intuition and verification. He ponders the knowledge he possesses and tries to push it further, he guesses and checks his guess, he conjectures and confirms or explodes his conjecture. These guesses and conjectures are by no means leaps in the dark; for knowledge once gained casts a faint light beyond its own immediate boundaries. There is no discovery so limited as not to illuminate something beyond itself. The force of intellectual penetration into this penumbral region which surrounds actual knowledge is not, as some seem to think, dependent upon method, but upon the genius of the investigator. There is, however, no genius so gifted as not to need control and verification. The profoundest minds know best that Nature’s ways are not at all times their ways, and that the brightest flashes in the world of thought are incomplete until they have been proved to have their counterparts in the world of fact. Thus the vocation of the true experimentalist may be defined as the continued exercise of spiritual insight, and its incessant correction and realization. His experiments constitute a body, of which his purified intuitions are, as it were, the soul.”

Theories, however helpful, should be held with a loose hand. He declares:--

“In our conceptions and reasonings regarding the forces of nature, we perpetually make use of symbols which, whenever they possess a high representative value we dignify with the name of theories. Thus, prompted by certain analogies, we ascribe electrical phenomena to the action of a peculiar fluid, sometimes flowing, sometimes at rest. Such conceptions have their advantages and their disadvantages; they afford peaceful lodging to the intellect for a time, but they also circumscribe it, and by-and-by, when the mind has grown too large for its lodging, it often finds difficulty in breaking down the walls of what has become its prison instead of its home.”

In the same vein was the remark of Michael Faraday:--“I cannot but doubt that he who as a mere philosopher has most power of penetrating the secrets of nature, and guessing by hypothesis at her mode of working, will also be most careful for his own safe progress and that of others, to distinguish the knowledge which consists of assumption, by which I mean theory and hypothesis, from that which is the knowledge of facts and laws.”

He once wrote a letter on ray-vibrations to Mr. Richard Phillips; at its close he said:--“I think it likely that I have made many mistakes in the preceding pages, for even to myself my ideas on this point appear only as the shadow of a speculation, or as one of those impressions on the mind which are allowable for a time as guides to thought and research. He who labors in experimental inquiries, knows how numerous these are, and how often their apparent fitness and beauty vanish before the progress and development of real natural truth.”

“Summing up, then,” says Professor William Stanley Jevons, in “Principles of Science,” “it would seem as if the mind of the great discoverer must combine almost contradictory attributes. He must be fertile in theories and hypotheses, and yet full of facts and precise results of experience. He must entertain the feeblest analogies, and the merest guesses at truth, and yet he must hold them worthless until they are verified in experiment. When there are any grounds of probability he must hold tenaciously to an old opinion, and yet he must be prepared at any moment to relinquish it when a single clear contradictory fact is encountered. ‘The philosopher,’ says Faraday, ‘should be a man willing to listen to every suggestion, but determined to judge for himself. He should not be biassed by appearances; have no favorite hypotheses; be of no school; and in doctrine have no master. He should not be a respecter of persons, but of things. Truth should be his primary object. If to these qualities be added industry, he may indeed hope to walk within the veil of the temple of nature.’”

Character, no less than mind of the highest order, ever distinguishes the great researcher. Says Professor Tyndall:--“Those who are unacquainted with the details of scientific investigation, have no idea of the amount of labor expended on the determination of those numbers on which important calculations or inferences depend. They have no idea of the patience shown by a Berzelius in determining atomic weights; by a Regnault in determining co-efficients of expansion; or of a Joule in determining the mechanical equivalent of heat. There is a morality brought to bear upon such matters, which, in point of severity, is probably without a parallel in any other domain of intellectual action.”

Surely there was a union of the highest character and of consummate ability in Stas, the Belgian chemist, who eliminated from his chemicals every trace of that pervasive element, sodium, so thoroughly, that even its spectroscopic detection was impossible.

A Word for Discursiveness.

The greatest man of science that England has given to the world was Sir Isaac Newton, second only to him was Dr. Thomas Young, who established the wave-theory of light, who deciphered Egyptian hieroglyphics with marvelous skill, and was withal an accomplished physician. In 1801 he was appointed to the professorship of natural philosophy in the Royal Institution, London, founded in 1800 by Benjamin Thompson, Count Rumford, a native of Woburn, Massachusetts. When Dr. Young died, Davies Gilbert, president of the Royal Society, delivered a commemorative address in the course of which he declared that in Young’s opinion it is probably most advantageous to mankind that the researches of some inquirers should be concentrated within a given compass, but that others should pass more rapidly through a wider range. He believed that the faculties of the mind were more exercised, and probably rendered stronger, by going beyond the rudiments, and overcoming the great elementary difficulties, of a variety of studies, than by employing the same number of hours in any one pursuit--that the doctrine of the division of labor, however applicable to material product, was not so to intellect; and that it went to reduce the dignity of man in the scale of rational existences. He thought it impossible to foresee the capabilities of improvement in any science, so much of accident having led to the most important discoveries, that no man could say what might be the comparative advantage of any one study rather than of another; though he would have scarcely recommended the plan of his own course as a model to others, he still was satisfied in the method which he had pursued.