454 ANTIENT METAPHYSICS. Book V. 



and yet it is neccfiaiy that they flioukl be confiderctl, if we have a 

 mind to view the fubje<5t in 4ts full extent. I will begin with the 

 moft fimple of thefe Hypothefes, which is, that the Central Bodies 

 attradl: the Planets that go round them ; by which I underftand 

 that they do really attrad them, in the proper etymological fenfe of 

 the word. This Hypothefis might be ftill farther funpliiied, by fup- 

 pofmg, as I have faid, that the Central Bodies not only attra£l the 

 Planets to them, but make them perform the whole Motion round 

 them, as the hand not only draws the ftone in the fling to it, but 

 makes it go round: For, if a Body, at the diftance of thoufimds of 

 miles, can draw another to it, why fliould it not be able, likewife, 

 to make it go round it? But, as it is commonly underftood only 

 to attraft the Planet, there muft. be another Motion in the Projedile 

 Line, by Bodily Impulfe; fo that the Motion is neceffarily com- 

 pounded. I will only add further, to what I have faid upon this 

 fubje£t, that, if there be any truth in this Hypothefis, of Body ad- 

 ing upon Body at a diftance, it is one of the greateft difcoveries in 

 modern times; for no antient philofopher ever dreamed that Body 

 could a£l upon Body, without being in contadt with it, either me- 

 •diately or immediately, any more than that a Body, once fet in Mo- 

 tion by Impulfe, would continue in Motion for ever, by virtue of 

 that Impulfe. 



The next fuppofition, grafted upon this third Plypothefis, is, I 

 think, poffible, which, I mufl confefs, I think the other is not ; 

 namely, that the Planet is moved in the Line of Projedlion by Pul- 

 fion, and, in the Centripetal Line, by PuHion likewife ; but with 

 this difference, that, in the Line of Projedion, one Pulfion is fuffi- 

 cient to make the Body go on for ever, with the fame velocity ; 

 whereas, in the Centripetal Line, as the velocity is conftantly in- 

 creafing, repeated pulfations are neceflary. This fyflem has fo far 

 the merit of uniformity and fimplicity, that it not only employs the 



5 fame 



