PRINCIPLE OF NATURAL SELECTION. 22 J 



From a logical point of view the work of the 

 last thirty years in the various fields of biology 

 has been a series of deductions and verifica- 

 tions of the original propositions laid down 

 by Darwin. He saw from the beginning that 

 belief in his theory must rest on general con- 

 siderations, the chief of which was its power 

 to facilitate deductive investigation; and there 

 it still rests. At this late day the chief apostle 

 of natural selection says that it is really diffi- 

 cult to imagine the process of natural selection 

 in its details, and that it is impossible to this 

 day to demonstrate it in any one point. 1 It 

 is the logical relation of the principle to the 

 facts that makes it invaluable in modern 

 thought. The whole logical history of Dar- 

 win's principles illustrates what Mill said of 

 the deductive method. "To the Deductive 

 Method thus characterized in its three con- 

 stituent parts, Induction, Ratiocination, and 

 Verification, the human mind is indebted for 

 its most conspicuous triumphs in the investiga- 

 tion of nature. To it we owe all the theories 

 by which vast and complicated phenomena are 

 embraced under a few simple laws, which, con- 

 sidered as the laws of these great phenomena, 



1 Weissmann, Contemporary Review, September, 1893, Vol. 

 LXIV. p. 322. 



