320 THE COMING OF AGE OF 



following of ardent disciples who are occupied in spread- 

 ing and developing its doctrines. Mere insanities and 

 inanities have before now swollen to portentous size 

 in the course of twenty years. Let us rather ask this 

 prodigious change in opinion to justify itself; let us 

 inquire whether anything has happened since 1859, 

 which will explain, on rational grounds, why so many 

 are worshipping that which they burned, and burning 

 that which they worshipped. It is only in this way 

 that we shall acquire the means of judging whether 

 the movement we have witnessed is a mere eddy of 

 fashion, or truly one with the irreversible current of 

 intellectual progress, and, like it, safe from retrogres- 

 sive reaction. 



Every belief is the product of two factors : the first 

 is the state of the mind to which the evidence in favour 

 of that belief is presented; and the second is the logi- 

 cal cogency of the evidence itself. In both these re- 

 spects, the history of biological science during the last 

 twenty years appears to me to afford an ample explana- 

 tion of the change which has taken place ; and a brief 

 consideration of the salient events of that history will 

 enable us to understand why, if the "Origin of Spe- 

 cies " appeared now, it would meet with a very different 

 reception from that which greeted it in 1859. 



One-and-twenty years ago, in spite of the work com- 

 menced by Hut ton and continued with rare skill and 

 patience by Lyell, the dominant view of the past history 

 of the earth was catastrophic. Great and sudden physi- 



