454 TiiE SENSORIAL FUNCIIONS. 



AUliough tlie corporeal or physical change taking 

 place in the sensoriom, and the mental affection we 

 term sensation, are linked together by some inscru- 

 table bond of connexion, they are, in their nature, 

 as perfectly distinct as the subjects in which they 

 occur ; that is, as 7nin(l is distinct from matter ; 

 and they cannot, therefore, be conceived by us as 

 having the slightest resemblance the one to the 

 other. Yet sensations invariably suggest to the 

 mind ideas, not only of the existence of an external 

 agent as producing them, but also of various qua- 

 lities 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 con- 

 cerning the origin, the formation, and the laws of 

 our perceptions. This vast field of curious but dif- 

 ficult inquiry, situated on the confines of the two 

 great departments of human knowledge, (of which 

 the one relates to the phenomena of matter, and the 

 other to those of mind,) requires for its successful 

 cultivation the combined eftbrts of the physiologist 

 and the metaphysician. For although our sensations 

 are purely mental affections, yet inasmuch as they 

 are immediately dependent on physical causes, 

 they are regulated by the physical laws of the 

 living frame; whereas the perceptions derived from 

 these sensations, being the results of intellectual 

 processes, are subject rather to the laws which re- 

 gulate mental than physical phenomena. It is 

 certain, from innumerable facts, that in the present 



