CHAPTEE XIII. 



ENERGY AS ADEQUATE CAUSE OF MOTION. 



HERE, then, we have a further development of the 

 world as a self-measured whole. Each particular 

 phase can only act as it is in turn acted upon, and the 

 reaction is always precisely equal to the action. Every 

 force-center, then, may be said to have its own action 

 reflected back to itself. 



At the same time, the thorough-going externality of 

 the forces of nature is manifest in the fact that in every 

 phase of activity either side may be regarded indifferently 

 as action or as reaction ; though this, too, has its deep- 

 reaching suggestion that all action is equally reaction, and 

 that all reaction is itself a phase of the total initiative, or 

 spontaneous action. 



In fact, as has already become evident, it is only 

 through a balancing of action and reaction that force can 

 be force at all. The centripetal and the centrifugal 

 modes of force cannot exist, save in complete interfusion. 

 And, let us repeat, force can be force at all only through 

 acting. A force that does not act is not a force. And 

 force can act only as a strain against an opposing phase of 

 force. 



Evidently, then, the totality of " forces" in the uni- 

 verse must be completely self-balanced. Equilibrium is 

 the only possible condition in which the totality of 

 energy can be conceived as existing. 



143 



