DARWIN, AND THE ORIGIN OF SPECIES 209 



ledge adds anything to our nature more or less than belief that 

 the brain is made to vibrate in tune with nature by vibrating in 

 tune with nature ? Is this belief any more significant or any more 

 instructive than belief that the brain is made to vibrate in tune 

 with nature by the " Pickwick Papers " ? 



It may be well to dwell a little on the assertion that what we 

 know as truth is merely the vibration of a brain in tune with 

 nature ; and to ask what these words mean. Vibrations are said 

 to be demonstrated when, directly or indirectly, we are made to 

 perceive them by our senses ; nor do I suppose that Romanes 

 could ask or hope for better proof of his assertion than the 

 demonstration, to our senses, of the actual vibration of a brain 

 in tune with nature whenever a truth arises in the mind. 

 Whether we share his confidence that this proof will be found 

 in the next two hundred years or not, we may ask what it would 

 mean, if found. 



It is a truth that stones are heavy, and the vibration of a 

 brain in tune with heaviness under the visual stimulus of a stone 

 would be a response ; but we know no reason why extended 

 bodies should have weight, except that the fact is so. With- 

 out, at present, asking Berkeley's old question whether sensible 

 vibrations of the brain or of anything else can exist otherwise 

 than in a mind, may we not ask whether the vibration of the 

 brain in tune with heaviness would tell us why we should think 

 the thought that stones are heavy, any more than the fact that 

 stones are heavy tells us why they should be .'' Would the sen- 

 sible perception of the vibrations of our brains in tune with 

 nature, whenever a truth arises in our minds, tell us anything 

 except that, with experience, comes knowledge .'' Would it be any 

 reason why this should be the case except that the fact is so .'' 

 And do we not now all admit this as a fact .-' 



We have good reason to hope that practical advantage to 

 mankind will follow progress in the physiology of the brain, as 

 it has followed all progress in natural knowledge ; although it is 

 hard to see what use there could be in proof that truth is the 

 vibration of a brain in tune with nature, unless we also discover, 

 outside our brains, some way to tell when their vibrations are in 

 tune. 



