LUCRETIUS AND THE ATOMIC THEORY 209 



refraction and reflection. To any one of his blind compeers 

 who objected that such a supposition as an influence starting 

 from an amazing distance, occupying no sensible time in the 

 traject, transmitted, reflected, and refracted without the inter- 

 ference of one ray with another, was either miraculous or absurd, 

 and wholly unworthy of consideration as a physical hypothesis, 

 he would have answered : Light exists for all that, and its laws 

 I can prove to you by mathematical reasoning from experiment. 

 He would have been perfectly right, as he was about gravitation, 

 but that need not have prevented subsequent philosophers from 

 devising the undulatory theory of light if they had been clever 

 enough ; quite similarly, the fact that gravitation as discovered 

 by Newton does exist need not prevent our trying to devise a 

 scheme which shall explain its action, starting from much 

 simpler postulates than that of a universal influence of each 

 atom on all others at a distance. 



The action of a body on its neighbour can be explained 

 without the idea of a force acting even across a small void, by 

 the simple assumption that two bodies cannot be in the same 

 place at the same time, an assumption only tacitly made by 

 Lucretius, and generally received as undeniable, though it 

 admits of rational doubt, for experiment is by no means conclu- 

 sive as to its certainty. Still, most people will be and have 

 been unable to doubt it. With this assumption, motion and 

 influence of all kinds can be transmitted either through a fluid 

 constituting a plenum, or from one atom to another, as they 

 clash in a vacuum. By successive blows or extended currents 

 action can produce results at a great distance from its origin 

 upon either of these hypotheses, without the assumption that 

 matter can act where it is not. Some explanation of gravity 

 may be found requiring only the above assumption coupled with 

 the other dogma, that matter once in motion will continue to 

 move till stopped, and no atomic theory can be received as 

 complete which does not explain gravitation as one of its con- 

 sequences. 



Lesage, a Genevese, undertook to deduce the laws of gravi- 

 tation as a necessary consequence of the atomic theory, revert- 

 ing, however, to the chaotic motion of atoms in all directions 

 taught by Democritus, instead of the rectilinear parallel motions 

 VOL. I. P 



