THE NEWTONIAN PHILOSOPHY. 537 



impenetrability, and even extenfion *. The efTence of Mind, on 

 the other hand, they faid, confifted in aHivity : And therefore body- 

 is primarily and originally moved by Mind : But it is alfo,at fecond 

 hand, moved by body ; and this in two different ways, as 1 have ob- 

 ferved, either by trufion or by pulfion. 



In one or other of thefe ways body is moved, according to the doc- 

 trine of antient philofophy. When Mind is immediately and diredly 

 the caufe of the motion, it is evident that this caufe muft adt conliantly 

 and inceflantly .while the motion continues ; and I will venture to fay, 

 that we have no idea of Mind moving body otherwife : And when it 

 is moved by trufion, or the preffure of another body upon it, the 

 caufe, in the fame manner, operates conftantly and inceflantly, while 

 the motion continues. But, what Ihall we fay of motion by puiiion, 

 or i^Uy as Sir Ifaac exprefles it t ? How is it continued after the pul- 

 fion that produced it has ceafed ? To fay that the pulfion is the 

 caufe of it, is an anfwer that may pafs with a vulgar man ; but it will 

 not fatisfy a philofopher, who will fay that pulfion was indeed the 

 caufe of the beginning of the motion, but never can be the caufe of 

 its continuance ; for nothing that has ceafed to exift can be the caufe 

 of any thing prefent ; fo that, to fay that the pulfion is ftill the caufe 

 of the motion, is to fay, in effed, that the motion is without any 

 caufe. And, indeed, to fay that an efficient caufe, fiich as pulfion is 

 of motion, produces any effed, without operating, or, what is the fame 

 thing, after it has ceafed to operate, is to fpeak without ideas. And the 

 fame holds with refped to other efficient caufes. Thus, an artift is the 

 efficient caufe of the work he produces ; but, after his operation has 

 ceafed, he is not the caufe of the continuance of that work, nor of any 



Y y y move- 



• See what I have faid upon this fubjeO under the difference beturixt matter and 

 body, chap. r. book 2. p. 53. and chap. 2. p. 6j. 



+ Definit. 4. lib. i. 



