334 FROM THE GREEKS TO DARWIN 



domesticated products, by printed inquiries, by 

 conversation with skilful breeders and gardeners, 

 and by extensive reading." This is the most de- 

 liberate and rigid instance of the application of 

 the inductive method which we have met with in 

 our whole study of the contributors to the evo- 

 lution theory. 



Darwin soon perceived the force of artificial 

 selection as the secret of man's success in form- 

 ing useful races of animals and plants; and in 

 October, 1838, while reading Malthus on popu- 

 lation, the idea of selection in a state of Nature 

 first occurred to him as the result of the struggle 

 for existence, or rather for life, between differ- 

 ent individuals and species. Four years later he 

 briefly set down his views, and in 1844 he allowed 

 himself to write out his progress. He had already 

 reached the main line of argument of his Origin 

 of Species, including the now familiar tripod of 

 his theory — Struggle, Variation, and Selection; 

 he had also reached his principle of sexual selec- 

 tion, yet under the influence of the- French evo- 

 lutionists he "attached somewhat more weight to 

 the influence of external conditions in producing 

 variation, and to the inheritance of acquired hab- 

 its than in the ^Origin.' "^ 



At this time Darwin naturally began to look 



iSee Life and Letters, 1896, vol. I, pp. 375-6. This was Huxley's 

 observation upon this essay in reply to a request for a criticism 

 from the editor. This essay should be published. 



