# Popular Science Monthly/Volume 52/December 1897/The Life History of Scientific Ideas

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* THE LIFE HISTORY OF SCIENTIFIC IDEAS.
By M. GUSTAVE LE BON.
SCIENTIFIC ideas are subject to the same general law of evolution which we have expounded as to other ideas in a previous paper (The Work of Ideas in Human Evolution, Popular Science Monthly, vol. xlviii, August, 1895); but being less lasting than other ideas, the study of them is easier. Science does not escape the general laws that regulate the elements of every civilization. These laws, too, are derived from a small number of fundamental ideas variable in different epochs, and which stamp a deep mark on every science. All modern physics rests upon the idea of the indestructibility of energy; biology on the idea of transformation by selection, and pathology on that of the action of the infinitely little. It is a property of scientific ideas that they have a force much less relative than that of religious, political, and moral ideas, but they lack much of being absolute truths; and that is why we see the directing ideas of science usually changing every fifty years. All these ideas are most frequently nothing but provisional hypotheses. The only veracious side of them is that they explain for the given moment the largest number of the facts. Darwin's hypothesis of the evolution of living beings explains more facts than Cuvier's hypothesis of successive creations; and the hypothesis of luminous undulations explains more phenomena than the hypothesis that preceded it.
It does not matter that these great directing ideas are erroneous. If we place ourselves at the point of view simply of the advance of the human mind, it will hardly be a too rash assertion to say that error is infinitely more useful than truth. Absolute truths, or what are considered such, are not discussed any more and provoke no investigation. Ideas held as hypotheses, on the other hand, provoke much. The researches made for the purpose of defending or attacking the hypothesis of the emission of light and that of undulations begat the finest discoveries of optics. The much-debated hypothesis of transformism has produced more research within a few years past than was made in all the centuries gone before. During the epoch, on the other hand, when what Aristotle and Ptolemy wrote was held for gospel truth, there could be no research; and for several centuries science was contented with traditions and made no progress. The most fruitful method of investigation is by imagining some hypothesis and trying to verify it, and by modifying it as new facts come to light. The great advantage of scientific ideas is that their value can be speedily ascertained by experiment, while that of ​religious, political, and moral ideas is determined very slowly. We should not, however, suppose that they are established and vanish with any extreme rapidity. Their evolution is indeed more rapid than that of other ideas, but it follows the same phases. Its history shows that although they address themselves only to the most enlightened minds, it takes them not less than twenty-five years, and usually much longer, to establish themselves. The clearest of them, the least hypothetical, those most easy to demonstrate, those which would seem least subject to controversy, like the doctrine of the circulation of the blood, have not been accepted in less time. In other respects scientific ideas are established under the influence of the factors we have described as acting with other ideas—affirmation, repetition, contagion, and prestige—and perhaps we may add, since we are dealing with the scientific category, reasoning; but the action of this factor is so weak that we might properly omit it. When it intervenes it is chiefly to refute an accepted idea, not to establish a new one. The new scientific idea is rarely imposed, so far at least as the majority of minds are concerned, by demonstration. It must not be supposed that because a man cultivates science he is released from the yoke of established dogmas. Scientific dogmas are often the most tyrannical of all.
The scientific idea is pre-eminently established by the prestige of the man who imposes it, and rarely in any other way. When Charcot introduced to science the phenomena of animal magnetism, which had been described for more than a century by students whose only fault was that they had no prestige, and whose admirable researches had been neglected for that reason by many generations of doctors, shall we suppose that the demonstrations of the professor were what convinced the medical public? Not at all, for the same demonstrations had been repeated thousands of times within a hundred years. The conviction was simply the result of the prestige of the expert, who did nothing but introduce into official science a series of phenomena which were perfectly known before him. After having been established by prestige the scientific idea goes through the ​regular course of evolution. It is taken up by apostles who propagate it in a small circle, and it begins to spread. It at first meets with strong opposition, for it strikes forcibly against many ancient and established things. The apostles who have adopted it are excited by this opposition, which only persuades them of their superiority over the rest of men, and they defend it with energy, not, indeed, because it is true—for they generally know nothing about that—but simply because they have adopted it. The new idea is discussed and is accepted in whole by some and rejected in whole by others. Affirmations and negations are exchanged, but very few arguments; the only motives for the reception or rejection of an idea being, for the immense majority of minds, simply those of feeling, in which reasoning has no part. In consequence of these passionate contestations the idea progresses slowly. The young people who become aware of the contest adopt the idea readily, for the single reason that it is contested. To youth, eager to be independent, wholesale opposition to things that are accepted is the most easily accessible form of originality. The idea therefore continues to gain. As it is gradually accepted by official men of science it at length becames propagated wholly by the mechanism of contagion, and insinuates itself, timidly at first, and then boldly, into the classical books. Its triumph is then complete. Like religious dogmas, it becomes a part of the things that are not disputed. We have only to recollect the history of transformism in Trance, and how the scandalous heresy has passed into the state of a classic dogma, to observe the successive series of these phases of propagation.
After having prevailed for a considerable length of time the idea begins to lose its hold and at last dies out. But before an old idea is wholly destroyed it has to go through a series of retrogressive transformations that require many generations for their accomplishment. Before vanishing forever it takes its turn in forming a part of the old hereditary ideas which we qualify as prejudices, but respect nevertheless. The old idea, although it is already nothing but a word, a sound, a mirage, possesses a magical power that still subjects us. At last it dies. After reigning long over a civilization ideas lose their prestige, fade away, and are extinguished. New discoveries disturb them. Belief in them becomes less general. Men begin to discuss them, and by the mere fact of discussion their death is near. Every great directing idea being generally a fiction, they can not submit to be discussed except on condition of never being subjected to critical examination. But even when an idea has been violently disturbed the institutions derived from it retain their vitality and are effaced very gradually. When it has completely lost its ​power all that it upheld soon falls. It has not yet been given to any people to change their ideas without being at once forced to transform all the elements of their civilization.—Translated for the Popular Science Monthly from the Revue Scientifique.