Chap. IL ANTIENT METAPHYSICS. 6i 



muft have fomething peculiar to Itfelf, which makes it what it is, and 

 nothing elfe, and is the foundation of all its idiojjiatical qualities, as 

 they may be called, by which it is diftinguiQied from every fubflance 

 of the fame fpecies : And, when we add to all this, that thofc fimilar 

 qualities of natural fubilances by which we detine them, are only fuch 

 as affedt our fenfes, and which, therefore, are fuperficial, and far re- 

 moved from the internal ftrmfture of the thing, it is perfe(^ly evident, 

 that we can have no idea of the ejjential form of any fuch fubftance : 

 And, indeed, it muft be obvious to cor.nion fenfe, that it is impoflible 

 I can know the effence of any individual thing, by only knowing that 

 it refembles other things in certain qualities which affedt our fenfes j 

 and what is true of individuals, mult neceiTarily be true of genufes 

 and fpeciefes, fmce it is from individuals that we form our ideas of 

 them. 



And here again we may fee the juflice of Plato's obfervation above 

 quoted, * That^ in this ftate of our exiftence, we fee things only as in 

 * a dream ;' for we fee not the fubftance of any thing, but only fha- 

 dows as it were, or likenefles and refemblances. And it may ferve to 

 juflity a method of reafoning which he frequently ufes, and particu- 

 larly in the TitiKsus, from images or fimilitudes ; for all our ideas are 

 truly nothing more than fimilitudes, denoting the likenefs that one thing 

 has to another. 



And fo much for form, the other principle of natural bodies. To 

 thefe Ariflotle has added a third, which he calls ^Ti^r.rt-,, or priva- 

 tiojif an addition that he has thought proper to make to the Py- 

 thagorean and Platonic philofophy, in order to give his fyftem the ap- 

 pearance of novelty; but without any necefTuy, as I apprehend ; for it 

 is not a caii/e, as he himfeU admits, fuch as niittcr and form, but is 

 only that without which the firft fnatler could not receive the impref- 

 fion of siny form ; for it muft be clear of every Jorm, which is what he 

 calls privation, before it can admit any. Now, this is necelfaiily implied 



in 



