86 ESSAYS awn OBSERVATIONS 
Activity may be varioufly applied. An acti- 
on may be with-held by an oppofite and equal 
action, as in the cafe of two contrary preflures: 
or, it may be employed in deftroying the ef- 
fect of fome former action, as when it ftops 
or retards a moving body. But the genuine 
characteriftic of an active being, is a power 
of beginning motion either in itfelf or ano- 
ther, without the means of preceeding mo- 
tion*. Thus a man from a ftate of reft can 
begin a motion which fhall move another 
body: or he can begin a motion which fhall 
ftop or retard another motion. And it will 
readily be admitted, that whatever active be- 
ing can thus begin motion in another, without 
the means of previous motion, will of courfe 
be able to confume motion in another, with- 
out receiving any itfelf. 
WHEN one body ftrikes upon another and 
moves it, we commonly indeed call this an 
action: yet there is no refemblance between 
this mechanical communication of motion, | 
and 
* All mer: mechanical communications of motion, are not 
Properly action, but mere pafivenc/s, both in the bodies that 
impell, and that are impelled. ion is the beginning of a 
motion where there was none before, from a principle of 
life or aStivity. Clark’s Lett. to Leibnitz p. 327- 
