THE LIFE HISTORY OF SCIENTIFIC IDEAS. 253 



regular course of evolution. It is taken up by apostles who propa- 

 gate 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 ex- 

 cited by this opposition, which only persuades them of their superi- 

 ority 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 feel- 

 ing, in which reasoning has no part. In consequence of these pas- 

 sionate 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 in- 

 sinuates 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 France, and 

 how the scandalous heresy has passed into the state of a classic 

 dogma, to observe the successive series of these phases of propa- 

 gation. 



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 accomplish- 

 ment. 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 discov- 

 eries 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 vital- 

 ity and are effaced very gradually. When it has completely lost its 



