Chap. III. ANTIENT METAPHYSICS. 357 



by which he certainly means the Celeftial Motions, were not produ- 

 ced by any original Force impreflcd upon them, but only by the 

 continual exertion of Mind, if he had not underftood that the pro- 

 jcdile or progrefTivc Motion, by which the Planet h carried on, was 

 not produced by any original imprellcd Force ; for Gravitation docs 

 no more than dircdt the ProgrcfTive Motion, and binder it from 

 going on in a flraight line. And, indeed, it is evident to mc, that 

 he had in his view Sir Ifaac's Firft Law of Motion, though he does 

 not mention it, (out of regard, it is likely, to Sir Ifaac, with whom 

 he lived in great friendfhip\ by which the Motion of the Planets, 

 once begun, was to go on forever, by virtue of the original impulfc, 

 without any further agency of Mind or Body. 



The next authority 1 flxall quote is that of a living author, Dr 

 Horfley, not a lefs authority, in my opinion, than that of Dr Clarke. 

 He is well known as a Mathematician ; and he is likewife a fchobr, 

 and, in my opinion, an excellent philofopher, having fludied the 

 antient as w^ell as the modern philofophy. He has favoured me 

 with fome obfervations upon the Firft Volume of my Metaphyfics ; 

 and, indeed, without the encouragement and the inftru£lion I have 

 got from him, I believe I ftiould not have perjTifted in my attempt to 

 revive the Antient Philofophy, nor troubled the world with this Se- 

 cond Volume of Metaphyfics. Though he muft be fuppofed to be 

 greatly prejudifed in favour of Sir Ifaac, yet he is fo candid as fairly 

 to acknowledge, that Sir Ifaac's Firft Law of Motion cannot be de- 

 fended upon the principles of found philofophy ; and he has furnifti- 

 cd me with the argument that I have fo much infifted on, from the 

 nature of Motion, which I will here give in the Doctor's own words, 

 exprefled with all the clearnefs and brevity of a Geometer. * 1 be- 

 * lieve, with the Author of the Antient Metaphyfics, that fome ac- 

 ' tive principle is neceflary for the continuance, as well as for the 

 ' beginning of Motion. I know that many Newtonians will riot 



' allow 



