14 x\NTIENT METAPHYSICS. Book I. 



Having thus fhown the nature of Sir Ifaac's doctrine of motion, 

 and to what confequences it tends, I will now prove that it has no 

 foundation in nature ; and this I think may be proved both a priori^ 

 from the nature of motion, and from fadl and obfervation. 



And, Jirjl, as to the nature of motion ; wherever any thing is 

 moved, there mufl; be both adlion and paffion in the cafe, that 

 is, there rauft be fomeihing that moves, or adls, and fomething 

 that is moved, that is fuflfers or is paflive ; for adlion and paffion 

 are relatives. Now, there can be no relation except betwixt two 

 things at lead ; for we cannot conceive the fame thing as relating 

 to itfelf. And, therefore, the fame thing cannot, at the fame time 

 and in the fame refpedt, both ad and fuffer : So that the fame body 

 cannot both move and be moved at the fame time ; and, therefore, 

 •when we fay that an animal moves itfelf, we muft not underftand 

 that the body of the animal moves itfelf, but that it is moved by the 

 mind of the animal. 



I will here fay no more upon this argument, from the nature of 

 the thing, which, I think, is demonftrative; but I will refer the reader 

 to what I have laid at foine length in the firft Vol. of this Work, 

 Book 2. Chap. 3. — where I have faid a great deal of the Category 

 of Relation, and proved, I think, moft clearly, that it can only fub- 

 fift betwixt two different things ; and have illuftrated it by exam- 

 ples *. 



But adion and paffion, fuch as moving and being moved^ are not only 

 relatives, but are oppoiites ; fo that it is (\ill more inconceivable how 

 they fhould exift in the fame fubjed: at the fcime time : For though 

 contraries, fuch as heat and cold, may exifl, and often do exifl, 

 in the fame fubjed, it is at different times ; but it is abfolutely in- 

 conceivable 



* Page 69. 



