AND ITS SELF-CONSERVATION. 135 



Still further, in direct opposition to the Zenonian 

 opinion that motion is impossible, it assumes on the con- 

 trary that rest is impossible. And this again follows evi- 

 dently from the conception of the extended world as 

 constituted by and of force. For force, to be force at all, 

 must act, and the action of force must necessarily involve 

 motion. 



But let us inquire what are the further implications of 

 this second law of motion. And first we have to notice 

 more explicitly that the second law is but the positive ex- 

 pression of what is negatively announced in the first. The 

 first law declares substantially that no body has the power 

 to move itself. If it moves it must be moved from with- 

 out; that is, by an "impressed force/' But if its change 

 of motion depends wholly on impressed forces, then it 

 will follow that the change of motion must be propor- 

 tioned to the impressed force, and take place in the direc- 

 tion in which the force acts. And this is precisely what 

 the second law positively affirms. Thus it appears that 

 the first and second laws of motion are merely the posi- 

 tive and negative aspects of the same fundamental prin- 

 ciple of the extended world. 



But this fundamental principle is an all-pervasive one. 

 We have already seen that every force-center is necessa- 

 rily related to every other force-center; that, in fact, 

 each force-center is in its full significance an infinitely 

 extended sphere, which again but indicates the concrete 

 aspect of continuity in force manifested as "matter/' 



This same conception indeed is otherwise expressed 

 in the universal law of gravitation which declares in effect 

 that every body is concretely related to every other body. 

 Every body or force-center, then, acts on every other body 



