134 THE WORLD-ENEKGY 



indifference. The extended is the indifferent, the uncon- 

 scious, and is therefore capable of action only by way of 

 reaction. And even thus its action, according to this 

 law, is still only of the most external character. It is 

 primarily nothing more than a change of space-relation 

 mere motion of translation. 



But again, since the movement can take place only 

 from external impulse, it is evident that the direction and 

 quantity of the motion will depend upon that impulse. 

 In other words the motion must, both in direction and in 

 quantity, be directly and absolutely proportioned to the 

 impressed force. 



Here, then, is a further fundamental condition of all 

 actual motion. And this condition is formulated in what 

 is known as the 



SECOND LAW OF MOTION. 



Newton's statement of this law is that: " Change of 

 motion is proportional to the impressed force, and takes 

 place in the direction of the straight line in which the 

 force acts." 



This statement, it will be noticed, assumes that all 

 bodies are in motion, and that motion can therefore never 

 be produced, but can only undergo change. This change, 

 however, can only take place by transferrence by one 

 body giving up its motion to another. For thus only can 

 we conceive a force to be "impressed" upon a given 

 body. But this amounts to saying that on the whole 

 motion can neither be increased nor diminished, that the 

 total quantity of motion in the physical universe must 

 forever remain unchanged. 



