PERCEPTION. 361 



utter ignorance of the nature of those actions; and all our 

 knowledge on this subject is limited to the changes which 

 we are conscious are going on in the mind. It is to these 

 mental changes, therefore, that our attention is now to be 

 directed. 



In experiencing mere sensations, whatever be their as- 

 semblage or order of succession, the mind is wholly passive: 

 on the other hand, the mind is active on all occasions when 

 we combine into one idea sensations of different kinds, (such 

 as those which are derived from each separate sense,) when 

 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 different from that in which they 

 were originally presented. Many of these active operations 

 of mind are implied in the process of perception; for al- 

 though it might be supposed that the diversity in the nature 

 of our sensations would sufficiently indicate to us a corre- 

 sponding variety in the qualities of the material agents, 

 which produce their impressions on our senses, yet these 

 very qualities, nay, even the existence of the objects them- 

 selves, 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 

 existence, 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 undulations 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 con- 

 tact with the auditory nerve. It is not difficult to prove 

 that the objects of perception are mere creations of the mind, 

 suggested, probably instinctively, by the accompanying sen- 

 sations, but having no real resemblance or correspondence 

 either with the impressions themselves, or with the agencies 



VOL. II. 46 



