Chap. VI. ANTIENT METAPHYSICS. 409 



demoriftrated by Geometry, and by Lines and Figures, I fhould be 

 very ill qualified for the taflc I have undertaken. But the philofo- 

 phical reader will readily diftinguifh betwixt the Science and the Me- 

 taphyfical Principles upon which it is founded ; for, as I have ob- 

 ferved more than once in the courfe of this Work, the principles of 

 every inferior Science are to be fouixl in Mctaphyfics, or the Firft 

 Philofophy. And it is undoubtedly true, what Ariftotle has faid, 

 that none of thefe Sciences demonflrates its own principles. Thus, 

 for example, the principles of Euclid's Geometry never can be de- 

 monftrated by Lines and Figures, which arc the only fubjecl of 

 Geometry, but muft be fought for in the Firft Philofophy, where 

 we learn what Extenfion and what Body are, what Quantity is, and 

 how the two fpeciefes of it, viz. Magnitude^ and Quantity Difcrete 

 or Number^ are to be diftinguiihed from one another; — how 

 Body differs from its Dimeniions ; — -what Length, Breadth, and 

 Depth are ; — and how it comes that a Point has no Parts. * Thefe 

 are Speculations which Euclid has not meddled with, and which 

 convinces me, that Euclid muft either have been a philofopher him- 

 felf, or been under the direction of a philofopher in forming his 

 Syftem ; for it is the bufmefs of philofophy to difcriminate the feveral 

 Sciences, and to fix the bounds of each f. But let us fuppofe that 

 Euclid had not been fo v/ell inftru6te3, but had run his Geometry 

 up into Metaphyfics, as the Newtonians have done their Aftronomy, 

 I think, wuth as little neceffity ; — and let us fuppofe, further, that he 

 had gone wrong in laying down thofe Metaphyfical principles, and 

 had philofophifcd as ill as fome modern philofophers have done. 

 Vol. II. F f f concerning 



* See what I have faid upon the Principles of Geometry, Vol. I. Lib. v. Cap. -8. 



■j- The accurate difcrimination that Ariflotle has made of the feveral branches of 

 philofophy in the difl'crent Arts and Sciences, is one of the things that I admire 

 much in that great philofopher ; particularly, he has diftinguifhed very accurately 

 three Arts, which have a great connection together, and which very few, who 

 think themfelves philofophers, are able to dillinguifli ; I mean Logic, Dialectic, and 

 Rhetoric. 



