I PROLOGUE 41 



I have hitherto dwelt upon scientific Naturalism 

 chiefly in its critical and destructive aspect. 

 But the present in carnation of the spirit of the 

 Renascence differs from its predecessor in the 

 eighteenth century, in that it builds up, as well 

 as pulls down. 



That of which it has laid the foundation, of 

 which it is already raising the superstructure, is the 

 doctrine of evolution. But so many strange mis- 

 conceptions are current about this doctrine it is 

 attacked on such false grounds by its enemies, and 

 made to cover so much that is disputable by some 

 of its friends, that I think it well to define as 

 clearly as I can, what I do not and what I do 

 understand by the doctrine. 



I have nothing to say to any "Philosophy of 

 Evolution." Attempts to construct such a phil- 

 osophy may be as useful, nay, even as admirable, 

 as was the attempt of Descartes to get at a theory 

 of the universe by the same a priori road ; but, in 

 my judgment, they are as premature. Nor, for 

 this purpose, have I to do with any theory of the 

 " Origin of Species," much as I value that which 

 is known as the Darwinian theory. That the 

 doctrine of natural selection presupposes evolution 

 is quite true ; but it is not true that evolution 

 necessarily implies natural selection. In fact, 

 evolution might conceivably have taken place 

 without the development of groups possessing the 

 characters of species. 



