18 ESSAYS ayn OBSERVATIONS 
fiftance made in the change from reft to mo- 
tion, or from motion to reft. And it is e+ 
qually obvious, ‘that a ftate of motion is very 
different from a ftate of reft ; and that the 
preferving a body in motion, muft be an o- 
peration of a different kind, from that of 
preferving it at reft. 
In order to handle this fubjet with fome 
degree of accuracy, I fhall endeavour to make 
out the three following propofitions: frff, 
That motion is a continued ation, which 
muft infer fome power continually ating. 
Secondly, That as matter refifts a change from 
re{t to motion, as well as from motion to reft, 
this refiftance is not to be accounted for by 
the mere negation of a caufe, but is a pofi- 
tive effect to require a caufe as much as mo- 
tion does. And, Ja/tly, after explaining the 
caufe of the continuance of motion, I thal! 
endeavour to fhow, that itis an effect of a 
different kind from the refiftance which mat- 
ter exerts againft any impulfe which puts it 
in motion. 
Wirs regard to the firft propofition, mo- 
tion evidently differs from the other proper- 
ties of matter. It is not like extenfion, fi- 
gure, and fuch like qualities effential to mat- 
