Characters as Adaptive and Specific. 183 



been- done with such brilliant success both by Daiwin 

 and Wallace, as well as by many of their followers. 

 But this is a very different thing from laying down 

 the universal maxim, that in all cases utility must 

 be present, whether or not we shall ever be able to 

 detect it ^ For this universal maxim amounts to an 

 assumption that natural selection has been the " exclu- 

 sive means of modification." That it has been " the 

 main means of modification " is proved by the gener- 

 ality of the observed facts of adaptation. That it has 

 been " the exclusive means of modification." with the 

 result that these facts are universal, cannot be thus 

 proved by observation. Why, then, is it alleged? 

 Confessedly it is alleged by way of deduction from 

 the theory of natural selection itself. Or, as above 

 stated, after having deduced the theory from the facts, 

 it is sought to deduce the facts from the theory. 



Thus far I have been endeavouring to show 

 that the universality of adaptation cannot be inferred 

 from its generality, or from the theory of natural selec- 

 tion itself. But, of course, the case would be quite 

 different if there were any independent evidence — or 

 rather, let us say, any logical argument — to show that 

 natural selection is " the exclusive means of modifi- 

 cation." For in this event it would no longer involve 

 circular reasoning to maintain that all specific char- 

 acters are likewise adaptive characters. It might 

 indeed appear antecedently improbable that no 

 other principle than natural selection can possibly 

 have been concerned in the differentiation of those 

 relatively permanent varieties which we call species — 

 that in all the realm of organic nature, and in all the 

 ' See Introductory Chapter, p. ao. 



