LAWS OF MIND. 503 



ideas, not to consist of them. Our idea of an orange 

 really consists of the simple ideas of a certain colour, a 

 certain form, a certain taste and smell, &c,, because we 

 can by interrogating our consciousness, perceive all 

 these elements in the idea. But we cannot perceive, 

 in so apparently simple a feeling as our perception of 

 the shape of an object by the eye, all that multitude of 

 ideas derived from other senses, without which it is 

 well ascertained that no such visual perception would 

 ever have had existence; nor, in our idea of Extension, 

 can we discover those elementary ideas of resist- 

 ance, derived from our muscular frame, in which Dr. 

 Brown has rendered it highly probable that the idea 

 originates. These therefore are cases of mental che- 

 mistry: in which it is proper to say that the simple 

 ideas generate, rather than that they compose, the 

 complex ones. 



With respect to all the other constituents of the 

 mind, its beliefs, its abstruser conceptions, its senti- 

 ments, emotions, and volitions ; there are some (among 

 whom are Hartley, and the author of the Analysis) 

 who think that the whole of these are generated from 

 simple ideas of sensation, by a chemistry similar to 

 that which we have just exemplified. I am unable 

 to satisfy myself that this conclusion is, in the 

 present state of our knowledge, fully made out. 

 In many cases I cannot even perceive, that the line 

 of argument adopted has much tendency to esta- 

 blish it. The philosophers to whom I have referred 

 have, indeed, conclusively shown that there is such a 

 thing as mental chemistry; that the heterogeneous 

 nature of a feeling, A, considered in relation to B and 

 C, is no conclusive argument against its being gene- 

 rated from B and C. Having proved this, they pro- 

 ceed to show, that where A is found, B and C were, 



