XV. 



LOGICAL HISTORY OF THE PRINCIPLE OF 

 NATURAL SELECTION. 



T^vARWIN'S own views of method, his treat- 

 L ^ ment of evidence, and some of the 

 various logical processes which he employed in 

 his investigations, having been discussed and 

 illustrated by examples from his many works, 

 it now remains necessary to trace the logical 

 history and examine the present logical status 

 of the principle of natural selection, which gave 

 inspiration to and lay at the basis of his life- 

 work. The theory of natural selection has per- 

 meated and colored modern thought more deeply 

 than perhaps any other scientific theory, and 

 this fact alone makes the study of its logical 

 history extremely interesting. 



The scientific influences, both in the form 

 of teachers and of books, to which Darwin was 

 exposed during and after his university life, 

 were opposed to the already well known doc- 

 trine of the descent of species. Various reasons 

 have been assigned for the failure of the doc- 



