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:—