PHYSICAL AND LITERARY. 95 



fclf ? No doubt, we commonly fay in the 

 mechanical philofophy, that one body ads 

 upon another by impulfe, and the other 

 reaas upon it. Nay, Sir Ifaac Newton 

 himlclf fpeaks of matter ading by inertia, 

 or vis inertits, which, tranflated literally, 

 would feem to import an impotent pow- 

 er, or adive inactivity. Such terms can- 

 not eafily be avoided, without introducing 

 endlefs circumlocutions. If more accu- 

 rate expreffions can conveniently be fub- 

 flituted in their place, it would be no dif- 

 fervice done to philofophy. But we are 

 not to difpute about words, when the 

 meaning is clear ; or to confound things 

 entirely diftind, becaufe they happen fre- 

 quently to be called by the fame name. 

 The true diftindlion between adtive force, 

 properly fo called, and the vis inertia^ 

 feems to confift in this, that fome beings 

 can begin motion where there was none 

 before, either in themfelves, or in the bo- 

 dy to be moved : In other beings, the 

 motion, when begun from fome excernal 

 caufe, is continued I'or want of a power to , 

 ftop it. The fiid of theib may be proper- 

 ly 



