SCIENTIFIC THOUGHT 25 



of his book, in which he says : " Some have even 

 imagined that Natural Selection induces variability 

 whereas it implies only the preservation of such 

 variations as arise, and are beneficial to the being 

 under its conditions of life." If Natural Selection 

 cannot cause a variation as, of course, it cannot 

 it is quite clear that, if it is an explanation at all, 

 it is not a complete explanation. But is it even a 

 partial explanation, and if so what actually does 

 it explain ? 



Driesch, in those valuable lectures which he 

 delivered in a Scottish University under the Gifford 

 Trust, points out that Natural Selection 



" can only eliminate what cannot survive, what 

 cannot stand the environment in the broadest 

 sense, but that Natural Selection never is able to 

 create diversities. It always acts negatively only, 

 never positively. And therefore it can explain [he 

 continues], if you will allow me to make use of 

 this ambiguous word it can c explain ' only why 

 certain types of organic specifications, imaginable 

 a -priori, do not actually exist, but it never explains 

 at all the existence of the specifications of animal 

 and vegetable forms that are actually found. In 

 speaking of an ' explanation ' of the origin of the 

 living specific forms by Natural Selection, one 

 therefore confuses the sufficient reason for the 

 non-existence of what there is not, with the 

 sufficient reason for the existence of what there is. 

 To say that a man has explained some organic 

 character by Natural Selection is, in the words of 

 Nageli, the same as if someone who is asked the 



n^y.. ..j. jjr / / / 



