PERCEPTION. 509 



cession ; for they are invariably found to be 

 dependent on the healthy state, not only of the 

 nerve, but also of the brain : thus, the destruc- 

 tion, or even compression of the nerve, in any 

 part of its course between the external organ 

 and the sensorium, totally prevents sensation ; 

 and the like result ensues from even the slight- 

 est pressure made on the sensorium itself. 



Although the corporeal or physical change 

 taking place in the sensorium, and the mental 

 affection we term sensation, are linked together 

 by some inscrutable bond of connexion, they 

 are, in their nature, as perfectly distinct as the 

 subjects in which they occur; that is, as mind 

 is distinct from matter ; and they cannot, there- 

 fore, be conceived by us as having the slightest 

 resemblance the one to the other. Yet sen- 

 sations invariably suggest to the mind ideas, 

 not only of the existence of an external agent 

 as producing them, but also of various qualities , 

 and attributes belonging to these agents ; and 

 the term Perception expresses the belief, or 

 rather the irresistible conviction, thus forced 

 upon us, of the real existence of these external 

 agents, which we conceive as constituting the 

 material world. 



Various questions here present themselves 

 concerning the origin, the formation, and the 

 laws of our perceptions. This vast field of 

 curious but difficult inquiry, situated on the 



