14 ANTIENT METAPHYSICS. Book I. 



of our fenfes, and, by confequence, our Ideas, which all arlfe from thofe 

 perceptions; fo that the philofophy oi" mind is likewife, In this refped, 

 founded upon tnotioju There is nothing, therefore, In philofophy,, 

 which it Is of greater importanccL to underliand well, than the nature 

 of motion. 



According to Mr Locke, there can be no definition of motion^ be- 

 caufe It is what he calls an idea of fenfation ; that is, in proper philo- 

 fophical language, a perception of fenfe. If this be true, there cannot, 

 for the fame reafon, be any definition, nor, by confequence, any fci- 

 ence of any of the fubjefts of natural philofophy ; for they are all 

 perceived by the fenfes, as well as motion. Sounds for example, is 

 perceived by the ear^ as motion is perceived both by the ear and eye^ 

 and even by the touch ; therefore, according to Mr Locke's dodrine, 

 there Is o^ found neither art nor fclence : Nay, there can be no fcience 

 even of geometry ; for the fubjeds of geometry are ideas, which are 

 all abftraded from perceptions of fenfe, from whence all our know- 

 ledge of every kind is derived. If, therefore, thtre be any truth at all 

 in Mr Locke's obfervatlon, it is this, that there can be no fcience of 

 the particular perceptions of fenfe; but we mufl: firft form, by abfirac- 

 tion, general ideas from thofe particular perceptions. But this may 

 be applied equally to every thing that is made the fubjed: of fcience. 

 Let us try, therefore, whether we cannot make of motion an objed of 

 intelled, or wlicthcr It mufl: continue always to be perceived only by 

 the fenfes, in the fame manner that it is perceived by the brute ani- 

 mals. 



The objeds of Intelled being fomething fixed and permanent. It 

 feems at firft ImpofTible to make an objed of intelled of a thing fo 

 fleeting and tranfitory as motion^ which is not one moment the fame 

 thing, butcxifts by perpetual change and variation. But there is one 

 thing which the intelled immediately apprehends in this fo change- 

 able 



