Chap. V. ANCIENT METAPHYSICS. 



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But the difference betwixt the two Motions is very great, in thig 

 refpedt, that the Motion of the projectile is begun by Bodily Im- 

 pulfe, whereas the Motion of the Planet is begun as well as carried 

 on by Mind : For, it is impoffible that an Immaterial Subftance, 

 which has no furface — can neither refifl: nor be refifted — and there- 

 fore cannot impell or be impelled, {hould begin Motion in that 

 way. And, not only is this evident from the Nature of the thing, 

 but from fa6b and experience : For we know, from the moft certain 

 of all knowledge, that it is not in that way that Mind moves Body, 

 being confcious that our Minds do not move our Bodies in that 

 way : And it is only by this Confcioufnefs, as I have elfewhere ob- 

 ferved *, that we have any idea at all of the Motion of Body by 

 Mind. If, therefore, there be no impulfe or Projedion of the Celef- 

 tial Bodies, it will follow, of neceflary confequence, that there is 

 no Gravitation ; for thefe two muft always go together : So that 

 the Motion of the Celeftial Bodies will not be compounded of Pro- 

 jedlion and Gravitation, as the Motion of Projediles is fuppofed to 

 be. 



But, 2do, in order to make out a perfed fimilarity betwixt the 

 Motion of Projediles and of the Planets, we muft fuppofe that the 

 Planets, before they were projeded, had that centripetal tendency 

 which the Projedile has, by which it is carried towards the centre, 

 with a force increafing, as the fquares of the diftance decreafe. 

 Now, this is mere hypothcfis, fupported by no fad or experience, 

 nor, I think, by any juft reafoning from analogy ; for, becaufe 

 the Bodies on the furface of our Planets have that tendency to the 

 centre of the Planet, we can never from thence juftly infer, that 

 the Planet itfelf, or other Planets, have that tendency towards the 

 fun. The fartheft, I think, that the argument from analogy can 

 go, is to fuppofe that the Bodies upon the furface of the other Pla- 

 nets have the fame tendency towards the centre of thofe Planets. 

 And even this analogical argument is by no means conclufive ; for 



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