ANIMAL AND RATIONAL INTELLIGENCE 161 



mind when a large admixture of physical activity 

 and experience is essential. This arises naturally 

 from the fact that we have no direct knowledge of 

 the working of brain and nerve, even when both are 

 in constant use. Hence we have to distinguish 

 between what is directly known in consciousness, 

 though standing unexplained by science; and what 

 is essential to our experience, yet known only by 

 scientific discovery, not by experience. The latest 

 results of physiological science have pressed into 

 notice the difference between the two phases of 

 activity, and the need for first explaining each se 

 parately, in order afterwards to explain their relation. 

 When we would interpret the action of human 

 intelligence, and thereby approximate towards some 

 clearer view of animal intelligence, all that belongs 

 to the structure and functions of our sensori-motor 

 system, including the correlated structure and 

 functions of the brain and subordinate centres, is to 

 be laid aside as unavailable. The only form of 

 dubiety hanging over our procedure, arises from 

 possible undiscovered brain functions, or functions 

 of inferior central bodies. But, admitting that 

 science has not yet completed interpretation of brain 

 functions, since silent regions stand unexplained, 

 it must be allowed that help cannot come in this 

 way towards solution of our problem. Direct know 

 ledge must determine our conclusions. We must 

 work towards inferences in the light of ascertained 

 facts. From the knowledge of our own intelligent 

 procedure, we must attempt an inference adequate for 

 explanation of what we take to be the intelligence of 

 the higher mammals ; and in order that the validity 



