PERCEPTION. 401 



course, will furnish a key to the solution of many 

 questions relating to perception, which have been 

 considered as difficult and embarrassing. 



The sensations derived from the different senses 

 have no resemblance to one another, and have, 

 indeed, no property in common, except that they 

 are felt by the same percipient being. A colour 

 has no sort of resemblance to a sound ; nor have 

 either of these any similarity to an odour, or a 

 taste, or to the sensations of heat, or cold. But the 

 mind, which receives these incongruous elements, 

 has the power of giving them, as it were, cohesion, 

 of comparing them with one another, of uniting 

 them into combinations, and of forming them into 

 ideas of external objects. All that nature presents 

 is an infinite number of particles, scattered in 

 different parts of space ; but out of these the mind 

 forms individual groups, to which she gives a unity 

 of her own creation. 



All our notions of material bodies involve that of 

 space ; and we derive this fundamental idea from 

 the peculiar sensations which attend the actions of 

 our voluntary muscles. These actions first give us 

 the idea of our own body ; of its various parts, and 

 of their figure and movements ; and next teach us 

 the position, distances, magnitudes, and figures of 

 adjacent objects. Combined with these ideas are 

 the more immediate perceptions of touch, arising 

 from contact with the siiin, and especially with 

 the fingers. All these perceptions, variously modi- 

 fied, make us acquainted with those mechanical 

 properties of bodies, wfiich have been regarded by 

 many as primary or essential qualities. The per- 

 ceptions derived from the other senses can only 



