Chap ir. ANTIENT METAPHYSICS. 75 



that informs each particular fubRance, though we know, in general, 

 that, as the Subftances are different, fo the Mind, which informs 

 them and conftitutes their eflence, mud alfo be different. It is, 

 therefore, true, in one fenfe, that we do not know the efTence of 

 any Subftance. But then we know efTentlal qualities of different 

 Subftances ; and by thefe we difcriminate one Subftance from ano- 

 ther. Thefe when we can difl.inguifli from accidental qualities, 

 which may exift in the thing, or not exift, and yet the thing conti- 

 nue the fame, we are faid to have the Idea of that thing. 



This diftindtion betwixt the internaiyorw, or the nature and ejfence 

 of the thing, and its material and accidental qualities, is the founda- 

 tion of the diftindlion betwixt Ideas and Senfations, laid down by the 

 two commerita'tors upon Ariftotle, Simplicius and Philoponus, which 

 I hold to be perfectly juft. The Nature or Eifence of the thing, fay 

 they, is perceived by the Mind, and by the Mind only, operating 

 without the Body; and therefore is the fubjedl of our Ideas : Whereas 

 the Accidents of any thing, which flow from its nature and eflence, 

 being perceived by the Senfes, are the fubjedl of our Senfations. 



With this diftindion, the difference betwixt Ideas and Senfations 

 may, I think, be made very clear, even with refped: to fubjeds of 

 ■which we have both ideas and ienfations, fuch as the fubjeds above 

 mentioned. But, before I come to apply it to particular examples, 

 I will make fome obfervations upon Ideas as they are confidered by 

 our modern philofophers. And, in the firft place, Ideas and Ab- 

 ftradl Ideas, are, in the language of that philofophy, confidered as 

 the fame thing, as if there could be no Idea that was not abftraded 

 from the matter with which it is incorporated. If that were the cafe, 

 favage nations would have no ideas at all, and very few of the vul- 

 gar among us. But the truth is, that we muft neccflarily fee the 

 Form or Idea in the Matter, before we can abftrad it ; for, how can 

 we abftrad from Matter what we do not know ? And the fad' is, 

 that, in the pradice of life, and even in pradical Sciences, fuch as 



K 2 natural 



