258 The Evolution Hypothesis. 



producing it? Either the cognition is a physical 

 phenomenon a new mode of matter and motion, or 

 the physical force which has passed into the intellec- 

 tion, and which has been expended in producing it, 

 has ceased to exist as physical force. If the physical 

 force continue to exist, then, on the principle of 

 correlation, the cognitive act cannot take place : the 

 persistence of force forbids it. If the physical force 

 operating in the brain pass into intellectual energy, 

 it must expend itself in the work, and we have so 

 much force taken out of the physical universe, and 

 transformed into an immaterial form in intellection. 

 This intellection may, in like manner, be transformed 

 back again into molecular motion ; in which case 

 the spiritual mode of being is robbed of so much 

 existence, while the material universe has restored 

 to it the former amount. Is not such an interchange 

 of the intellectual and physical of cognition and 

 motion, absurd ? Yet there is no other supposition 

 possible, if while we reject materialism we maintain 

 the correlation of mental and physical forces. The 

 correlation cannot come into play unless by the ex- 

 penditure of so much physical force in the production 

 of so much spiritual force, and vice versa the force 

 in either case passing into the new form. We con- 

 clude that it is not possible to bring into correlation 

 with physical forces the exercise of intellectual and 

 moral power. But if it be impossible to do so, it is 

 impossible to establish a universal law of evolution. 



