I04 EVIDENCES AND LIMITATIONS 



How did intelligence of any kind originate? The par- 

 ticular referred to is the impossibility of describing 

 mental phenomena in physical or mechanical terms. 

 If we concede that human intelligence is but a natural 

 evolution of animal sense, we are as far as ever from 

 accounting for the origin of intelligence by physical 

 evolution. If animal sense is nothing more than a 

 selected variation of the physical, it should be describ- 

 able in physical terms, which it certainly is not. The 

 wave motion of ether could never produce the sensa- 

 tion of light upon a bhnd spot, and blind matter is not 

 made sensitive to light or perceptive by mere mechanics. 

 Molecular action is one thing, sensation is another, and 

 the two differ in kind. No identical proposition can 

 be constructed in which the subject is sensation and the 

 predicate mere matter and motion, or vice versa, for 

 the two terms cannot be thought of as equivalent in 

 meaning. And if this is true of sensation at its lowest 

 stage, it is a fortiori and emphatically true of reflective 

 reason, of moral intuition, and of religious aspiration. 

 As I have already stated, the late Professor Huxley 

 was convinced that ''consciousness and molecular action 

 are capable of being expressed by one another." But 

 he frankly said, "Whether we shall ever be able to 

 express consciousness in foot-pounds, or not, is more 

 than I will venture to say." ^ A possibility which he 

 sees no prospect of being realized need not worry us. 

 In his later years he came to realize the utter unlike- 



^ Darwiniana, p. 163. On this whole argument, see H. Calder- 

 wood, Evolution, ch. xi. 



