PHYSICAL ann LITERARY. 5 
viz. to give a definition of a fimple idea. . 
They might as well have attempted a defini- 
tion of colour or found, of pain or any other 
{imple feeling. Itis to be regreted, that na- 
tural philofophers and mathematicians are 
not always well {killed in logics, and of this 
truth we fhall have but too often occafion to 
give examples. 
Sc aRcCE any author that I know has 
thought of giving a definition of reft; yet it is 
not a more fimple object than motion. TI can 
guefs at the reafon, that reft is the more fa- 
miliar object; a greater number of things 
appearing to be in a quiefcent ftate than in 
motion. If every thing about us appeared 
to move, we fhould be furprifed the’ firft 
time we faw a body at reft, and probably 
would endeavour to explain the thing to o- 
thers: but both are equally incapable of a 
definition. They are fimple objects of fight 
and perhaps of touch. Deprive us of thefe 
two fenfes, and we could never have the 
leaft notion either of reft or motion. 
WueEn a being moves itfelf or moves, we 
‘conceive the being as acting; and in this 
d view motion is a fpecies of action: » But, 
when a body is moved by being acted upon, 
ok we 
