PROPOSITION I. 



Force can act only between organized bodies of 

 material. 



To every action there is a reaction. 



If we lift a hundred-pound weight, our feet press 

 the ground with a hundred pounds additional pres- 

 sure. The engine must be bolted to the floor to 

 turn the shaft. When a boy throws a rock he 

 kicks the earth with his feet, and this may easily 

 be verified on a scale. The force that propelled the 

 rock came into play between the boy and the rock ; 

 the boy had to stand on something that did not 

 give way. And so, in every manifestation of force, 

 we may perceive, we must needs have two identities 

 perceptible directly to our senses. The great mass 

 of void matter contained in the Universe cannot be 

 the stable background from which force may act 

 or react upon, because every primary sphere of 

 void matter in the Universe can freely move out of 

 its place without hindrance ; and no change of posi- 

 tion of any organized body floating in that great 

 sea of unresisting primary spheres will make either 

 more or less room in the Universe. Neither can 

 the bodies, moving in unresisting primary spheres, 

 act as a stable base for the action of force, unless 

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