182 Darwin, and after Darwin. 



profound " ; and while, on this account, we ought " to 

 be extremely cautious in pretending to decide what 

 structures are now, or have formerly been, of use to 

 each species? in point of fact. " there can be little 

 doubt that the tendency to vary in the same manner 

 has often been so strong, that all individuals of the 

 same species have been similarly modified without the 

 aid of any form of selection 1 ." 



It will be my endeavour in the following discussion 

 to show that Darwin would have had an immeasurable 

 advantage in this imaginary debate. 



To begin with, Wallace s deductive argument is 

 a clear case of circular reasoning. We set out by infer- 

 ring that natural selection is a cause from numberless 

 cases of observed utility as an effect : yet, when " in 

 a large proportional number" of cases we fail to 

 perceive any imaginable utility, it is argued that 

 nevertheless utility must be there, since otherwise 

 natural selection could not have been the cause. 



Be it observed, in any given case we may properly 

 anticipate utility as probable, even where it is not 

 perceived ; because there are already so enormous 

 a number of cases where it is perceived, that, if the 

 principle of natural selection be accepted at all, we must 

 conclude with Darwin that it is " the main means of 

 modification." Therefore, in particular cases of un- 

 perceived utility we may take this antecedent prob- 

 ability as a guide in our biological researches as has 



1 Origin of Species, p. 72 : Mr. Wallace himself quotes this passage 

 (Darwinism, p. 141); but says with regard to it "the important word 

 'all' is probably an oversight" In the Appendix (II), on Danvin's 

 views touching the doctrine of utility I adduce a number of precisely 

 equivalent passages, derived from all his different works on evolution, 

 and every one of them presenting " the important word ' all.' " 



