Chap. IV. ANTIENT METAPHYSICS. 369 



on ? And, fo far we have already advanced in this inquiry, as to 

 have difcovered, that, fuppofing it to have begun by Impulfe of 

 Body, it could not go- on by that Impulfe merely, without fome 

 continued agency of either Body or Mind. 



As we can have no Idea of the Motions in the Heavens, but from 

 what we obferve here on earth, fo that our reafoning concerning 

 thofe Motions muft be all of the analogical kind, I will firfl; try to 

 difcover by what power the Motions here on earth are begun and 

 carried on. And 1 am fure the Newtonians will approve much of 

 this way of reafoning, as it is by the analogy betvt'ixt the Motions 

 of Projectiles here on Earth, and of the Celeftial Bodies, that Sir 

 Ifaac has afcertained the Law of the Planetary Motions. 



And, in the Jirji place, it is evident that the Bodies here muft ne- 

 ceflarily be moved in one of two ways ; for, either they muft move 

 themfelves, or they muft be moved by fomething different from 

 themfelves. Thofe that are moved in this latter way can only be 

 moved, either by other Bodies, or by Mind. There are, therefore, 

 only three ways in which it is poflible, by the nature of things, that 

 Bodies on this Earth can be moved j for they muft either move 

 themfelves, or they muft be moved by other Bodies, or, laftly, they 

 muft be moved by Mind *. 



Vol. II. A a a That 



* This way of reafoning, by enumeration of all poflible cafes relating to the 

 thing in queftion, one or other of which muft ncceflarily eicift, is very much ufed 

 by Ariftotle; and he commonly adds to the enumeration, «•< wa(» t««t« ..^r, 

 which I think I may add here : And, if it be fhown that none of the cafes can cxift 

 but one, the conclufion is demonftrative ; and, accordingly, it is a method of rea- 

 ibuing much ufed by the Mathematicians. 



