Chap. IT. ANTIENT METAPHYSICS. 19 



of another bodv, yet it is impoflible to fuppofe an infinite fucceffion 

 of bodies impelling one another; as then the caufes of motion would 

 be infinite, and, confequently, there would be no caufe at all that 

 could be affigned for the motion of any body. 



But Sir Ifaac appears not to have had fo much as the idea ot 

 motion by mind, as, I think, I have fhown from the account he has 

 given of the caufe of attraction or gravitation *, where, among the 

 various caufes that he affigns for this phaenomenon, which is the 

 grand principle of his philofophy, he does not fo much as mention 

 ni'iTid, though he is reduced to the neceflity of accounting for it 

 from a very extraordinary caufe, which to me is quite unintelligi- 

 ble f- The caufe 1 mean is " ethers^ ain^or fome we^//V/ra corporeal 

 or incorporeal, impelling the bodies, fwimming in it, towards one 

 another." Now, thofe who are more verfant in his philofophy than 

 I am may underftand how bodies can fwim in a medium incorpo- 

 real, and be impelled by that medium towards one another; but 

 to me it is quite unintelligible. I will only fay further upon 

 this fubjed:, that this phaenomenon of attraction, which is the 

 grand principle of Sir Ifaac's aftronomy, is, I think, of itfclf, de- 

 monftrative evidence of motion's being produced by mind: For it is 

 impoflible to conceive that bodies, fometimes at the greateft diflance, 

 can tend towards one another, by their action upon one another; 

 as we are as fure, as we can be of any thing perceived by our fen- 

 fes, that body can only a£t upon body by contadt. And this makes 

 Sir Ifaac's dodtrine of the motion of the Tides as unintelligible as his 

 dodrine of attradion: For he fays, that the flux and reflux of the 

 fea arifes from the adtion of the fun and the moonf. Now, how can 

 we conceive that thofe bodies, fo far removed from the fea, Ibould 

 adt upon it ? though we can very well conceive that the tides can be 

 moved, like other bodies, by mind, and in conformity with the 



C 2 motions 



* Vol. IV. p. 371. f See on this fubjeft, p. 10. of this vn! 



X Phji. Nat. prop. 24. theorem, 19, ^ 



