Chap; II. ANTIENT iMETAPHYSICS. 341 



fenfe of thofe Newtonians who yet defend this Firft Law of Mo- 



tion. 



And, if it be fo, I think it is evident that Sir Ifaac has ufed au 

 improper, as well as an unneceflary, expreffion, when he faid that 

 the Motion is carried on by a Vis Jnfita^ which certainly leads us to 

 believe that it is fome power inherent in the Body, which carries it 

 on. And, as he conftantly diftinguifhes it from the Vis Imprejfa^ 

 by which the Body is fet in Motion, I think it is plain that he be- 

 lieved the one power not to be intrinfic, or belonging to the nature 

 of Body, but extrinfic, or from without, as much as the impreflion 

 of a feal upon wax is, or any preffure or impulfe of one Body upon 

 another ; whereas the other Power by which the Body continues m 

 Motion, he confidered as intrinfic, and of the nature and effence of 

 Body. And this being the cafe, 1 confefs I am a little furprifed that 

 he has only faid barely, that he did not affirm Gravitation was ef- 

 fential to Body : Whereas he ought to have affirmed pofitively, as 

 Mr Cotes does in his Preface to his edition of the Principia, that it 

 •was an inherent quality of Body, and effential to it. And I am fure, of 

 the two, it has much better prctenfions to be of the nature and ef- 

 fence of Body, than what Sir Ifaac calls the Vis Injita : For Gravita- 

 tion adts always, and is the mod conftant Motion we know here on 

 earth ; whereas the Vis Injtta ads only occafionally when the Bodf 

 is impelled by another Body. 



I was once much difpofed to believe that Sir Ifaac, by the 7is In- 

 fita, which carries on the Motion of the Body after the impulfe has 

 ceafed, meant to denote Mind : But, upon confidering more at- 

 tentively his definition above mentioned, of this Vis Inftta^ I think it 

 is evident that he could not have that meaning ; for he makes it to 

 be a power by which Body continues in Reft, as well as in Motion. 

 Now, it is evident that it is not by Mind, but by its own nature and 



effence. 



