CHAPTER IV 



CAUSE AND EFFECT PROBABILITY 



^ I. — Mechanism 



The discussion of the previous chapter has led us to see 

 that law in the scientific sense only describes in mental 

 shorthand the sequences of our perceptions. It does not 

 explain ivhy those perceptions have a certain order, nor 

 why that order repeats itself; the law discovered by 

 science introduces no element of necessity into the 

 sequence of our sense- impressions ; it merely gives a 

 concise statement of how changes are taking place. That 

 a certain sequence has occurred and recurred in the past 

 is a matter of experience to which we give expression in 

 the concept causation ; that it will continue to recur in 

 the future is a matter of belief to which we give expression 

 in the concept probability. Science in no case can demon- 

 strate any inherent necessity in a sequence, nor prove 

 with absolute certainty that it must be repeated. Science 

 for the past is a description, for the future a belief ; it is 

 not, and has never been, an explanation, if by this word is 

 meant that science shows the necessity of any sequence of 

 perceptions. Science cannot demonstrate that a cataclysm 

 will not engulf the universe to-morrow, but it can prove 

 that past experience, so far from providing a shred of 

 evidence in favour of any such occurrence, does, even in 

 the light of our ignorance of any necessity in the sequence 

 of our perceptions, give an overwhelming probability 

 against such a cataclysm. If the reader has once fully 

 grasped that science is an intellectual resume of past 



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