THE LIFE HISTORY OF SCIENTIFIC IDEAS. 251 

 THE LIFE HISTORY OF SCIENTIFIC IDEAS. 



By M. GUSTAVE LE BON. 



SCIENTIFIC ideas are subject to the same general law of evolu- 

 tion which we have expounded as to other ideas in a previous pa- 

 per (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 hy- 

 potheses. The only veracious side of them is that they explain for 

 the given moment the largest number of the facts. Darwin's hy- 

 pothesis 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 attack- 

 ing 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 cen- 

 turies 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- 



