DEMONSTRATION, AND NECESSARY TRUTHS. 315 



found it quite easy to conceive, and which everybody 

 now knows to be true. There was a time when men 

 of the most cultivated intellects, and the most eman- 

 cipated from the dominion of early prejudice, could 

 not credit the existence of antipodes ; were unable to 

 conceive, in opposition to old association, the force 

 of gravity acting upwards instead of downwards. The 

 Cartesians long rejected the Newtonian doctrine of the 

 gravitation of all bodies towards one another, on the 

 faith of a general proposition, the reverse of which 

 seemed to them to be inconceivable the proposition 

 that a body cannot act where it is not. All the 

 cumbrous machinery of imaginary vortices, assumed 

 without the smallest particle of evidence, appeared 

 to these philosophers a more rational mode of explain- 

 ing the heavenly motions, than one which involved 

 what seemed to them so great an absurdity*. And 

 they no doubt found it as impossible to conceive that 

 a body should act upon the earth, at the distance of 

 the sun or moon, as we find it to conceive an end to 



* It would be difficult to name a man more remarkable at once 

 for the greatness and the universality of his intellectual powers, than 

 Leibnitz. Yet this great man gave as a reason for rejecting New- 

 ton's scheme of the solar system, that God could not make a body 

 revolve round a distant centre, unless either by some impelling 

 mechanism, or by miracle: "Tout ce qui n'est pas explicable" 

 says he in a letter to the Abbe Conti, " par la nature des creatures, 

 est miraculeux. II ne suffit pas de dire : Dieu a fait une telle loi 

 de nature; done la chose est naturelle. II faut que la loi soit exe- 

 cutable par les natures des creatures. Si Dieu donnait cette loi, par 

 exemple, a un corps libre, de tourner a 1'entour d'un certain centre, 

 il faudrait ou qu'il y joignit d'autres corps qui par leur impulsion 

 lolligeassent de rester toujours dans son orbite circulaire, ou qu'il mit 

 un ange a ses trousses^ ou en/in il faudrait quit y concourut extra- 

 ordinairement ; car naturellement il s'ecartera par la tangente." 

 Works of Leibnitz, ed. Dutens, iii. 446. 



