PERCEPTION. 457 



we compare sensations or ideas with one another ; 

 when we analyze a compound idea, and unite its 

 elements in an order or mode of combination dif- 

 ferent from that in which they were originally pre- 

 sented. Many of these active operations of mind 

 are implied in the process of perception ; for 

 although it might be supposed that the diversity in 

 the nature of our sensations would sufficiently indi- 

 cate to us a corresponding variety in the qualities 

 of the material agents, which produce their im- 

 pressions on our senses, yet these very qualities, 

 nay, even the existence of the objects themselves, 

 are merely inferences deduced by our reasoning- 

 powers, and not the immediate effects of those 

 impressions on the mind. We talk, for instance, of 

 seeing a distant body ; yet the immediate object of 

 our perception can only be the light, which has 

 produced that particular impression on our retina ; 

 whence we infer, by a mental process, the exist- 

 ence, the position, and the magnitude of that body. 

 When we hear a distant sound, the immediate 

 object of our perception is neither the sounding 

 body whence it emanates, nor the successive undu- 

 lations of the medium conveying the effect to our 

 ear : but it is the peculiar impression made by the 

 vibrating particles of the fluid, which are in direct 

 contact with the auditory nerve. It is not difficult 

 to prove that the objects of perception are mere 

 creations of the mind, suggested, probably instinc- 

 tively, by the accompanying sensations, but having 

 no real resemblance or correspondence either with 

 the impressions themselves, or with the agencies 

 which produce them ; for many are the instances 

 iii which our actual perceptions are widely different 



