52 THE WORLD-ENERGY 



Lastly, conceive the sphere to be the total quantity of 

 matter in the universe, in which case it is evident that we 

 should again have the total of attractions so reacting upon 

 itself as to unfold into an exactly balancing total of 

 repulsions. For in the physical universe as a whole (that 

 is, the only extended universe we can ever know) the sum 

 of reactions in attraction, just as the sum of reactions in 

 repulsion, must be equal to the sum of the actions. 



And the more fully to satisfy ourselves that this is the 

 case, we have only to repeat that the action of a force in 

 any given direction necessarily implies that there is resist- 

 ance to overcome. In other words, there can only be 

 action in so far as there is reaction. In the sum-total of 

 the physical world it could not, in the nature of things, 

 be otherwise than that " action and reaction are equal, 

 and in opposite directions." 



Thus, once more, attraction and repulsion prove to be 

 but the complementary modes of an all-pervading force or 

 energy, which constitutes the fundamental characteristic, 

 the inmost essence, of "matter" of whatever is real 

 and at the same time extended. They are thus the truly 

 essential " properties of matter." 



