THE DOCTRINE OF ENERGY 95 



The doctrine of Energy therefore puts in a new 

 and clearer light the whole theory of Causation. 



It is common for philosophers to talk of invariable 

 sequence as the criterion of Causality. But, in fact, 

 that is quite fallacious. No one ever regards a 

 phenomenon as the cause of another phenomenon. 

 We ascribe Causality to the energetic transmuta- 

 tion which in some form or other we inevitably 

 believe to accompany the appearance of every 

 phenomenon. We never postulate a causal relation 

 between day and night the most notable case 

 of invariable sequence. When we say the fire 

 warms the room, or the horse draws the cart, or 

 the sun ripens the corn, it is the Energy which 

 we rightly or wrongly associate with the visual 

 sensation referred to in the words " fire " and 

 " horse " and " sun " of which we are thinking, 

 and by no means of these visual sensations them- 

 selves. As has been well said, we never suppose that 

 the leading carriage of the train draws those behind 

 it, although their relation of sequence is quite as 

 close to it as to the engine. 



True, it is and must be from and by phenomena 

 only that I infer and measure the transmutations 

 of Energy, but the transmutations measured are 

 operations of the real thing-in-itself postulated 

 by Science. The existence of such Energy is 



