INFLUENCE ON RECENT SCIENCE 77 



chaotic masses are slowly changing into the more stable 

 form of stellar systems. 



Side by side with the belief in atoms, separated from 

 each other in empty space, had grown up the directly 

 contrary idea that substance is continuous and space 

 is a plenum. This doctrine permits us to make no 

 essential difference between space and matter. Space 

 becomes a continuous substance unvaried, and so im- 

 perceptible to our senses, while matter is merely a 

 localized variation of this same substance of such a 

 nature as to make it perceptible. And it is significant 

 of these two systems, that although they begin with 

 contradictory premises, they both lead to the same 

 conclusions after apparently rigorous deductions. 



The doctrine of continuity owes its rise to Hera- 

 clitus and, amongst the Greeks, was most highly de- 

 veloped by Aristotle. They announced this postulate 

 because the notion that a body can attract another 

 through an intervening vacuum and cause it to move 

 introduces an occult or inexplicable idea. Our experi- 

 ence teaches us that motion results only from a push or 

 impact between bodies actually in contact. But it is 

 quite evident, that in refusing to accept a force which 

 acts contrary to our experience, which all goes to show 

 that a material link is necessary to produce motion 

 between bodies, they fell into as serious a difficulty, 

 for they were compelled to create an occult substance 

 to serve as the material link between bodies, and occult 



