22 ESSAYS AND OBSERVATIONS 



power continually exerted to preferve a 

 body in motion. Again, if motion be con- 

 fidered as an effe6l, it can only be compa- 

 red to figure or colour, with regard to that 

 part of it which is paft : What part re- 

 mains to be performed, is fo far from a 

 compleated effedl, that it is not fo much 

 as commenced ; and therefore muft ne- 

 ceflarily be conceived as a different effeifl, 

 to the pro4u<!lion of which there muft be 

 a new exertion of power. Motion then 

 is a continued effect, or rather a feries 

 of different effeds, to require a caufe in 

 continue4 a<5lion. Accordingly, -when 

 •we attend to our own perceptions, we do 

 not inquire for a caufe, when a body cea- 

 fes to move, If the caufe of the motion 

 ceafe, we feek no other reafon for the 

 ceafing of the motion. If a thing fo evi- 

 dent can admit of illuftration, let us fi- 

 gure an animal in motion. It never 

 came into the mind of any perfon, that a 

 man is paffive in the adlion of walking 

 or running. In this cafe we reafon juft- 

 ly, that walking or running requires a 

 continued exertion of power. It requires 



no 



