xi.] MR. DARWIN'S CRITICS. 281 



when the man ceases to be conscious of them ? That 

 depends upon what is the essence and what the accident 

 of those operations, which, taken together, constitute 

 ratiocination. 



Now ratiocination is resolvable into predication, and 

 predication consists in marking, in some way, the exist- 

 ence, the coexistence, the succession, the likeness and 

 unlikeness, of things or their ideas. Whatever does 

 this, reasons ; and if a machine produces the effects of 

 reason, I see no more ground for denying to it the 

 reasoning power, because it is unconscious, than I see 

 for refusing to Mr. Babbage's engine the title of a 

 calculating machine on the same grounds. 



Thus it seems to me that a gamekeeper reasons, 

 whether he is conscious or unconscious, whether his 

 reasoning is carried on by neurosis alone, or whether 

 it involves more or less psychosis. And if this is true 

 of the gamekeeper, it is also true of the greyhound. 

 The essential resemblances in all points of structure 

 and function, so far as they can be studied, between 

 the nervous system of the man and that of the dog, 

 leave no reasonable doubt that the processes which go 

 on in the one are just like those which take place in 

 the other. In the dog, there can be no doubt that the 

 nervous matter which lies between the retina and the 

 muscles undergoes a series of changes, precisely analogous 

 to those which, in the man, give rise to sensation, a train 

 of thought, and volition. 



Whether this neurosis is accompanied by such psycho- 

 sis as ours, it is impossible to say ; but those who deny 

 that the nervous changes, which, in the dog, correspond 

 with those which underlie thought in a man, are accom- 

 panied by consciousness, are equally bound to maintain 

 that those nervous changes in the dog, which correspond 

 with those which underlie sensation in a man, are also 



