HI THE ORIGIN OF THE IMPRESSIONS 93 



am acquainted, contains nothing but a very odd 

 version of the physiological views of Descartes : 



"When I received the relations of resemblance, contiguity, 

 and causation, as principles of union among ideas, without 

 examining into their causes, 'twas more in prosecution of my 

 first maxim, that we must in the end rest contented with ex- 

 perience, than for want of something specious and plausible 

 which I might have displayed on that subject. 'Twould have 

 been easy to have made an imaginary dissection of the brain, 

 and have shown why, upon our conception of any idea, the 

 animal spirits run into all the contiguous traces and rouse up 

 the other ideas that are related to it. But though I have 

 neglected any advantage which I might have drawn from this 

 topic in explaining the relations of ideas, I am afraid I must 

 here have recourse to it, in order to account for the mistakes 

 that arise from these relations. I shall therefore observe, that 

 as the mind is endowed with the power of exciting any idea it 

 pleases ; whenever it despatches the spirits into that region of 

 the brain in which the idea is placed ; these spirits always 

 excite the idea, when they run precisely into the proper traces 

 and rummage that cell which belongs to the idea. But as their 

 motion is seldom direct, and naturally turns a little to the one 

 side or to the other ; for this reason the animal spirits, falling 

 into the contiguous traces, present other related ideas, in lieu of 

 that which the mind desired at first to survey. This change we 

 are not always sensible of ; but continuing still the same train 

 of thought, make use of the related idea which is presented to 

 us and employ it in our reasonings, as if it were the same with 

 what we demanded. This is the cause of many mistakes 

 and sophisms in philosophy ; as will naturally be imagined, 

 and as it would be easy to show, if there was occasion." (I. 

 p. 88.) 



Perhaps it is as well for Hume's fame that the 

 occasion for further physiological speculations of 

 this sort did not arise. But, while admitting the 



