222 THE PRINCIPLES OF SCIENCE. [CHAP. 



Logic the term cause seems to have re-asserted its old 

 noxious power. Not only does Mill treat the Laws of 

 Causation as almost coextensive with science, but he so 

 uses the expression as to imply that when once we pass 

 within the circle of causation we deal with certainties. 



The philosophical danger which attaches to the use of 

 this word may be thus described. A cause is defined as 

 the necessary or invariable antecedent of an event, so 

 that when the cause exists the effect will also exist or 

 soon follow. If then we know the cause of an event, we 

 know what will certainly happen ; and as it is implied 

 that science, by a proper experimental method, may attain 

 to a knowledge of causes, it follows that experience may 

 give us a certain knowledge of future events. But nothing 

 is more unquestionable than that finite experience can 

 never give us certain knowledge of the future, so that 

 either a cause is not an invariable antecedent, or else we 

 can never gain certain knowledge of causes. The first 

 horn of this dilemma is hardly to be accepted. Doubtless 

 there is iu nature some invariably acting mechanism, such 

 that from certain fixed conditions an invariable result 

 always emerges. But we, with our finite minds and 

 short experience, can never penetrate the mystery of 

 those existences which embody the Will of the Creator, 

 and evolve it throughout time. We are in the position 

 of spectators who witness the productions of a compli- 

 cated machine, but are not allowed to examine its inti- 

 mate structure. We learn what does happen and what 

 does appear, but if we ask for the reason, the answer 

 would involve an infinite depth of mystery. The simplest 

 bit of matter, or the most trivial incident, such as the 

 stroke of two billiard balls, offers infinitely more to learn 

 than ever the human intellect can fathom. The -word 

 cause covers just as much untold meaning as any of the 

 words substance, matter, thought, existence. 



Confusion of Two Questions. 



The subject is much complicated, too, by the confusion 

 of two distinct questions. An event having happened, we 

 may ask 



