6 Darwin, and after Darwin. 



Well, in the second place, Darwin has shown that 

 next only to the importance of clearly distinguishing 

 between facts and theories on the one hand, and of 

 clearly recognising the relation between them on the 

 other, is the importance of not being scared by the 

 Bugbear of Speculation. The spirit of speculation is 

 the same as the spirit of science, namely, as we have 

 just seen, a desire to know the causes of things. The 

 hypotheses non jingo of Newton, if taken to mean what 

 it is often understood as meaning, would express 

 precisely the opposite spirit from that in which all 

 scientific research must necessarily take its origin. 

 For if it be causes or principles, as distinguished from 

 facts or phenomena, that constitute the final aim of 

 scientific research, obviously the advancement of such 

 research can be attained only by the framing of 

 hypotheses. And to frame hypotheses is to specu- 

 late. 



Therefore, the difference between science and specu- 

 lation is not a difference of spirit ; nor, thus far, is it 

 a difference of method. The only difference between 

 them is in the subsequent process of verifying hypo- 

 theses. For while speculation, in its purest form, is 

 satisfied to test her explanations only by the degree 

 in which they accord with our subjective ideas of prob- 

 ability — or with the " Illative Sense" of Cardinal New- 

 man, — science is not satisfied to rest in any explanation 

 as final until it shall have been fully verified by an 

 appeal to objective proof. This distinction is now so 

 well and so generally appreciated that I need not 

 dwell upon it. Nor need I wait to go into any details 

 with regard to the so-called canons of verification. 

 My only object is to make perfectly clear, first, that 



