Introductory. 5 



distinction clearly in view, his idea of the scientific use 

 of facts is plainly that of furnishing legitimate material 

 for the construction of theories. Natural history is 

 not to him an affair of the herbarium or the cabinet. 

 The collectors and the species-framers are, as it were, 

 his diggers of clay and makers of bricks : even the 

 skilled observers and the trained experimentalists are 

 his mechanics. Valuable as the work of all these men 

 is in itself, its principal value, as he has finally de- 

 monstrated, is that which it acquires in rendering 

 possible the work of the architect. Therefore, although 

 he has toiled in all the trades with his own hands, and 

 in each has accomplished some of the best work that 

 has ever been done, the great difference between him 

 and most of his predecessors consists in this, that 

 while to them the discovery or accumulation of facts 

 was an end, to him it is the means. In their eyes it 

 was enough that the facts should be discovered and 

 recorded. In his eyes the value of facts is due to 

 their power of guiding the mind to a further discovery 

 of principles. And the extraordinary success which 

 attended his work in this respect of generalization 

 immediately brought natural history into line with the 

 other inductive sciences, behind which, in this most 

 important of all respects, she has so seriously fallen. 

 For it was the Origin of Species which first clearly 

 revealed to naturalists as a class, that it was the duty 

 of their science to take as its motto, what is really the 

 motto of natural science in general, 



Felix qui potuit rerum cognoscere causas. 



Not facts, then, or phenomena, but causes or prin- 

 ciples, are the ultimate objects of scientific quest. It 

 remains to ask, How ought this quest to be prosecuted ? 



