336 HABIT AND INTELLIGENCE. [chap. 



my argu- two remarks — that I have first rejected natural selection 

 ^^^ ' among spontaneous variations as a complete theory of the 

 origin of species, and afterwards gone on as if I thought it 

 true ; and that I treat intelligence as a Beus ex machind, 

 explaining vital phenomena, so far as I can, hy merely 

 physical causation, referring them to the action of external 

 agents, self-adaptation, and natural selection, and only 

 calling intelligence in as a sokition when the physical 

 causes fail to account for the facts. 



I shall reply to these two objections together. I believe, 

 as I have more than once stated already (and I think I 

 here state the universal belief of scientific men) — I believe, 

 Life does I Say, that the action of life does not supersede the ordi- 

 ^°d ^TT ^^^'^ physical laws of causation — or, in other words, does 

 works not supersede the ordinary properties of matter — but 

 tlie°pfo-' tl^^^ ^^^ produces its results of organization by guiding 

 perties of the action of causation, and by working through the 

 ordinary properties of matter. So it is with intelligence, 

 sointelli- As life works through- the inorganic forces, so intelli- 

 gence Pence, I believe, works through the unintelligent forces. 



with un- o ' ' o _ ° 



intelligent All the inorganic forces are unintelligent, and so, I 

 forces. -believe, are the laws of habit and variation. The rela- 

 These tion of life to the inorganic forces is totally inexplicable, 

 relations ^^ ^j^ relation of intelligence to the unintelligent forces 



are inex- ° " 



plicable. is equally so ; but the latter, though inexplicable, forms 

 We have part of our mental experience. Our mental life is partly 

 ™®?|^Jg^^j intelligent and partly merely habitual The intelligent 

 the action and voluntary powers of the mind, as I shall have to 

 genca ^^" show in a future chapter, do not supersede the action of 

 the habitual powers, but work through them ; and it is, 

 I believe, the same in our unconscious or bodily life. Self- 

 adaptation takes place according to the laws of habit, and 

 according to that remarkable physical law in vuiue of 

 which every part that has increased work thrown on it 

 within the limits of what is good for its health, increases 

 in size, in strength, and in general efficiency ; but it 

 appears to be universally admitted that there are many 

 adaptations for which no mere blind habitual process of 

 seK-adaptation will account. Natural selection also is a 



