58 'WHAT IS A SPECIES?* 



In leaving the dogma of 'special creation', and the 

 assumption of ' fixity of species ' with which it is bound 

 up, it is only right to point out how completely the 

 logical foundations of both were undermined by the 

 great thinker who has just passed away. Years before 

 the appearance of the Darwin-Wallace essay, and of the 

 Origin, Herbert Spencer wrote on The Development 

 Hypothesis} Although of course wanting the great mo- 

 tive power to evolution supplied by Natural Selection, 

 this essay is a powerful and convincing argument for 

 evolution as against special creation. It is astonishing 

 that it did not produce more effect. I may appropriately 

 conclude this section of the Address by quoting the 

 results of Herbert Spencer's critical examination, from 

 every point of view, of the Linnaean conception of the 

 origin of species. ' Thus, however regarded, the hypo- 

 thesis of special creations turns out to be worthless — 

 worthless by its derivation ; worthless in its intrinsic 

 incoherence ; worthless as absolutely without evidence ; 

 worthless as not supplying an intellectual need ; worthless 

 as not satisfying a moral want.' 2 



I now pass to the first idea contained in the Linnaean 

 conception : — that species are different from one another. 

 Stripped of the assumption that the differences were 

 determined by separate creation and of the assumption 

 that they are fixed for all time, this idea is no less than 

 the recognition of specific characters definable by the 

 method of Diagnosis. And it is only fair to remember 

 that if the theology of Linnaeus demanded the acceptance 

 of these assumptions, his life was really devoted to the 

 ceaseless study of animal and vegetable forms as a 

 foundation for the definition and grouping of species. 

 A discussion of the method of Diagnosis, its implications 



that a butterfly, which, when a resident in Madagascar, has a female the 

 image of itself, should, in West Africa, have one without any re- 

 semblance to it at all ' (Entomologist's Monthly Magazine, October, 1874, 



1 In the Leader, between January, 1852, and May, 1854, reprinted 

 in Essays Scientific, Political, and Speculative, London, 1868, vol. i, 



P- 377- 



B The Principles of Biology, London, 1864, vol. i, p. 345. 



