^2 D I S S E R T A T I O N O N 



Of this machine of the heavens, therefore, the two great motions, ac- 

 cording to Sir Ifaac, are, as 1 have faid, the proje^ile motion and gra- 

 vitation. But what are the moving powers which produce thefe mo- 

 tions ? And it is evident, from the principles laid down in the Prin- 

 cipia, as (hall be afterwards (hown, that Sir Ifaac fuppoles both to be 

 produced by bodily impulfe, with this difference, only, that the firfl is 

 produced by a fingle impulfe, the other by repeated impulies : '\nd this 

 is all we can learn of the moving power of this machine from the Princi- 

 pia, where he does not fo much as tell us of what kind the body is which 

 impells the planet, either in the line of projedionjor towards the cen- 

 ter. The machinery, therefore, of the heavens, as explained by him 

 an that work, is certainly very imperfect, as any account of a machine 



mull: 



The matter, I think, may be diftln£lly and fclentifically conceived In this way. 

 'When any body is movid, there muft neceffarily be a moving power, as nothing can 

 be produced without a caufe. This moving povi'er, according to my philofophy, is 

 Mind, of whofc nature and eflence it is to move, as much as it is of the nature and 

 cfTence of Boi'y to be moved. Now, Mind moves Body, either direclly and immedi- 

 ately, or it does not. If in the former wiiy, I fay the motion is not material cur 

 mechanical, but imm.'.terial, the mover being an immaterial power, and acting im« 

 mediately and directly : If in the other way, the motion is by the interven- 

 tion of other bodies, and is commonly communicated from Body to Body ; and 

 this motion I call material and mechanical. Of this kind are all the machines of 

 human conftruclion, becaufe all thofe machines are ultimately moved by Mind, ac- 

 cording to my philofophy, whatever name we may give to the moving power, calling 

 it Air, AVatcr, Fire, Weights, or Springs ; and of the fame kind are the machines 

 of Nature's workmanfhip, fuch as animal bodies, which are moved immediately by 

 mufclcs, fincws, and bones, but ultimately by Mind. To thefe two kinds of motion. 

 Sir Ifaac has been pUafed to add a third, which goes on, not cnly without the direct 

 and immediate agency of Mind, but without any agency at all of Mind, or of any 

 other power except the matter itfelf. This is Sir Ifaac's projectile motion of the pla- 

 nets. Whether there be any fuch thing in Nature as Body moved in this way, by its 

 own power, or by a vis ivfita^ as the Nev;tonians fpeak, I (hall afterwards inquire ; 

 but, in the mean time, fuppofing it to be fo moved, I call that motion likewife mate- 

 rial and mechanical \ for, though the motion be not communicated from Body to Body, 

 as in the cafe of machines commonly fo called, 1 do not know by what other name to 

 call it, in coatradiftiniflion to motion produced immediately and directly by Mind. 



