394 AN TIE NT METAPHYSICS. Book V. 



under ^ne line. And, therefore, he has begun his definitions of fi- 

 gures with the definition of a Circle, as the moft fimple of nil fi- 

 gures. Now, if the circle be a fimple figure, I think i^ follows of 

 neceflary confequence, that the Motion, which defcribes it, muft like- 

 wife be fimple. And, accordingly, Ariftotle every where fpeaks of the 

 Motion in a circle being as fimple as the Motion in a ftraight line. 

 The mlftake, I imagine, arifes from confounding the Circular or El- 

 liptical Motion produced by Body, with the fame Motion produced 

 by Mind, and not rightly underftanding the nature of Motion by 

 Mind ; for, if the Circular Motion is produced by Bodily Impulfe, it 

 is evident that the Motion will be a compounded Motion, as the 

 figure defcribed by it will not be a fimple figure, contained under one 

 line, but a figure of many lines, that is, a polygon : But the Mo- 

 tion by Mind being produced by inceflant energies, does not produce 

 a figure compofed of different fides ; and, as the figure is uncom- 

 pofed, fo is the Motion. 



• There is another reafon given why the Planetary Motion muft be 

 compofed, that otherwife the fimilarities, which Sir Ifaac Newton has 

 difcovered betwixt the Motion of the Planets and of Projedtiles, 

 could not exift. If this were true, I fhould think the argument 

 conclufive ; for, if I fee evidence of the exiftence of one thing, and 

 if it is proved to me that there is another thing which neceffarily 

 muft exift in confequence of the exiftence of the firft thing, it is to 

 me proof fufiicient that the other thing muft likewife exift. But, 

 without entering into this argument at prefent, as I intend to fay 

 more of it in the fequel, I will proceed to inquire, whether, upon 

 the fuppofition of the Motion of Projediles being a compounded 

 Motion, it neceflarily follows, that the Motion of the Planets is 

 likewife a compounded Motion, and that there is Projedion and 

 Gravitation in the Heavens, as well as on the Earth. And it will 

 be faid that this argument from the Projeftile Motion is the ftrong- 

 er, that, I fay, the Projedik Motion is carried en by Mind, as 

 well as the Motion of the Planets, 



But 



