| 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 re-
