Chap. V. ANTIENT METAPHYSICS. 411 



it eternal, the fuhjed of it muft, in like manner, be ftable and perma- 

 nent, without change or variation. 



Secondly^ We know nothing, as I have more than once faid, of the 

 nature and effence of body : We only know fome qualities or proper- 

 ties of it J and thefe, when attentively examined by the philofopher, 

 are no other than the perceptions of our mind, produced by the im- 

 preffion made by body upon our organs of fenfe ; or, as Mr Hobbes 

 has expreffed it, a tumult of the 7nind, excited by external things pref- 

 Jitig upon the organs of fenfe * ; which would be a good enough defi- 

 nition of fenfation, if it did not confound that tumult which the fenfa- 

 tion of pain or pleafure excites in the mind, with the fimple perception of 

 the objed. In ihort, all fenfation is nothing but the motion of external 

 things, affedting, in different ways, our minds. And, that thefe affec- 

 tions of our minds muff be very various and different, at different 

 times> is evident, from this confideration, that our fenfations muft ne- 

 ceffarily depend upon three things, /"r/?, the nature and difpofition of 

 the external objed which produces them ; fecondly^ the habit or dif- 

 pofition of the organ upon which theimpreffion is made, that is com- 

 municated to the mind ; and, thirdly, where the objedt ( perates upon 

 the organ, not immediately, but through a medium, as in the cafe of 

 feeing, hearing, and fmelling, the fenfation muft depend upon the 

 conftitution of that medium. 



Thus, it appears, that, in the perceptions themfelves, fo various and, 

 mutable, and depending upon fo many accidents, it is impoffible there 

 can be any fcience. And the only fcience that can be in the matter 



Fff2 is 



• Sufcitatits a rebus externis organa prementlbuSi animi tumultus. See the 

 paflage ouot-d at length, book 2. cap. 10. p. 14^ from whence It appears, that Mr 

 Hobbes falls into a much more dangerous error, when he confounds this tumult 

 with fcience and intellect. 



