i8 THE ORIGIN OF HUMAN REASON 



establish an d priori probability of an exactly opposite 

 kind. 



Though it is not true that all races of men, or that 

 most of them, are and still less have ever been, thus 

 continuously progressive ; and though it is true that a 

 certain enlargement of brain, and probably an increase 

 in practical intelligence, have taken place in animals, 

 yet the difference as to psychical advance between men 

 and animals is vast. In no species of mere animal have 

 we an approximation towards the evidence of advance — 

 since that species existed as a species — which is com- 

 parable with the advance which some races of men 

 have made. 



Herein we find a difference which we cannot measure, 

 and the probability which thence naturally arises is 

 that there must be a difference of kind, and not of 

 degree, between creatures whose capacities are so 

 extraordinarily diverse. 



Taking, then, these several a priori considerations 

 together, they must, in our opinion, be fairly held to 

 make out a very strong prima facie case in favour of 

 the view that there has been a positive interruption of 

 the developmental process in the course of psychological 

 history, and that the mind of man can never have been 

 evolved from the sensitive faculties of any brute. For 

 these considerations show, not only that on analogical 

 grounds such an interruption must be held to be in 

 itself probable, but also that there are facts with respect 

 to the human mind which are quite incompatible with 

 the supposition of its having been slowly evolved ; 

 seeing that no race in human history is known to have 



