Chap. XI. ANTIENT METAPHYSICS, 169 



Of the formation of ideas I have alfo faid a great deal in the 

 fourth vohime of this work*; and I will only add here, that as they 

 all arife from our fenfations, it is proper that we fhuuld know accu- 

 rately the nature of thefe fenlations. And there is, firft, the iinprcf- 

 fion made by external obje(5ls upon our organs of lenlation : In 

 this refpedl our mind is merely paffive. Next is the perception 

 of the objecfts themfelves, which make thefe impreflions upon 

 our organs : And "here the mind is adive; but it is only "our 

 animal mind, and therefore the brute has that perception as well 

 as we. Of thefe perceptions we form ideas in the manner I 

 have defcribed in the palllige quoted from the preceding volume, 

 where I have fhown that our ideas are the work of intelledt, and 

 therefore do not belong to the brute. It is for the want of making 

 thefe diftin^lions that Mr Locke has confounded fenfations and ideas, 

 and made a whole clafs of ideas, which he calls ideas of fcnfatlon. 

 Mr Locke's error, therefore, arifes from his not diftingulihing be- 

 twixt the materials of which our ideas are formed, tliat is o\\t fcn-^ 

 fat'ions^ and the ideas which are formed of them, and fo making 

 ideas of ouv fenfations. 



But though there be no ideas of fenfation, fuch aS thofc of Mr 

 Locke, there are ideas of another kind, and which are truly ideas 

 offenfation, though they be fuch ideas as very few can form. The 

 ideas I mean are thofe we form of the manner in which the objeds 

 of fenfe operate upon our organs of fenfe, and produce the differ- 

 ent perceptions we have of thofe objeds. For example, if we know 

 that we perceive objeds oi fight by the reflcdion of the rays of light 

 from thefe objeds to the pupil of our eyes, where ihey form au 

 image of the objed, which is perceived by the mind, the know- 

 ledge of this is what I call the idea of the /en/ation of fght. It 

 is, as I have faid, an idea which very few have formed : For it is 



Vol. VL Y truly 



" Book I. Clin p. I. VT. and VII. 



