4 ESSAYS AND OBSERVATIONS 



upon him to fet out with a definition of 

 motion. And, in a thing io fimple, it may 

 appear flrange to find fuch a variety of 

 definitions : Whence one thing may be ga^ 

 thered, that none of thofe definitions have 

 been approved of by fucceeding authors. 

 Epicurus defines motion to be *' a paiTage 

 ** from one place to another :" And he 

 might as well have defined it to be motion 

 from one place to another; becaufe paflage 

 in this fentence means nothing different 

 from motion. Sturmeus defines motion 

 to be ^^fticcejjwa ret motae in di'uerfts locis 

 " exiffentia" which is juftly blamed by 

 Leibnitz as defcribing theeffe(5l of motion, 

 rather than the formal nature of it. And 

 yet Leibnitz's own definition, " motus ejl 

 ** continua loci mutatio^' is not more fatis- 

 factory. But, of all the definitions that 

 ever were attempted, Ariftotle's definition 

 of motion is the moft unintelligible, " Ac- 

 ** tus entis in potentia quatenus in potentia'^'' 

 which Locke condemns as abfolute jargon; 

 and which, he fays, would puzzle any ra- 

 tional man, to whom it was not already 

 kinown by its famous abfurdity, to guefs 



■ , what 



