Chap. I. ANTIENT METAPHYSICS. 313 



by the knowledge of the laft, we know the nature of all things as they 

 actually exift. 



As this univerfal knowledge, which, as I have faid, diftinguifhes 

 philofophy from all particular fciences, is not to be calily underliood 

 by thofe who are entirely ignorant of the autient philofophy, I will, 

 for their fake, give an explanation of it from an author who has writ- 

 ten the beft introdudion to philofophy fhat ever was written, I mean 

 Ammonius Hermeiras, the fcholar of Proclus, and the mafler of both 

 Philoponus and Simpiicius, the two mod voluminous commentators 

 upon Ariftotle. In his commentary upon Porphyry's Introdudion, 

 p. 14. he thus explains how this univerfal knowledge is to be acquired: 

 ' It is impoffible,' fays he, ' to know each individual of any fpc- 

 ' cies, becaufe thefe are of number infinite and incomprehenfible, at 



* leaft to us ; and, in this refped, it is impoiTible to know all 



* things : But we may know the nature of the fpecies. Lvery par- 



* ticular man, for example, we canpot know ; but, if we know the de- 

 ' finition of man, we know the nature of man, of which every indi- 

 ' vidual of the fpecies participates ; and, in this fenfe, we may be faid 



* to know all men* The fame is true of horfes, dogs, and every other 



* animal we know. Further, the fpeciefes of animals, though not infi- 



* nite in number, are fo many, that it is impoffible we can know them 



* all, except by reducing them to one common nature ; and, in this 

 ' way, acquiring the idea of animal^ we may be faid to know all the 

 ' fpeciefes of animals, and, by confeq'uence, all the individuals under 



' thofe fpeciefes ; in fliort, all animals.-^ The fame is the procefs 



' of the human mind, with refped to vegetables, till we acquire the 



* idea of 'vegetable, by which we know all vegetables of every kind. 



* Further, if we would acquire knowledge ftill more comprehenfivc, 



* we try to form an idea more general, comprehending both animal 

 ' and vegetable, by endeavouring to dlfcover what they have in com- 

 ' men. In this way, w6 form the idea of the t« tu-h?c'», or of life 



R r * and 



