84 ESSAYS anv OBSERVATIONS 
Un ess this account of the continuation 
of motion can be fhewn to involve fome ab- 
furdity, why fhould. we feek for any other 
caufe of it, than the force impreffed by the 
external agent? . We may be told perhaps, 
«© That motion is a continued aétion:” and 
therefore body continuing to move, is active. 
But is not this either a begging of the que- 
ftion, or taking hold of the ambiguity of 
language to fupport it; inftead of. explain- 
ing, why a motion once excited fhould ceafe 
of itfelf? No doubt, we commonly fay in 
the mechanical philofophy, that one body 
acts upon another by impulfe, and the other 
reacts upon it. Nay, Sir I/aac Newton him- 
felf fpeaks of matter acting by inertia, or 
vis inertia, which, tranflated literally, would 
feem to import an impotent power, or adtive 
inactivity. Such terms cannot eafily be avoid- 
ed, without introducing endlefs circumlocu- 
tions. If more accurate expreffions can con- 
veniently be fubftituted in their place, it 
would be no differvice done to philofophy. 
But we are not to difpute about words, when 
the meaning is clear; or, to confound things 
entirely diftin@t, becaufe they happen fre- 
quently to be called by the fame name. The 
true 
