CAUSATION 



tlonal. When we judge that the succession of 

 night and day is a derivative sequence, depend- 

 ing on something else, we proceed on grounds 

 of experience. It is the evidence of experience 

 which convinces us that day could equally exist 

 without being followed by night, and that night 

 could equally exist without being followed by 

 day. To say that these beliefs * are not gener- 

 ated by our mere observation of sequence,' is 

 to forget that twice in every twenty-four hours, 

 when the sky is clear, we have an experimentum 

 crucis that the cause of day is the sun. We have 

 an experimental knowledge of the sun which 

 justifies us on experimental grounds in con- 

 cluding, that if the sun were always above the 

 horizon there would be day, though there had 

 been no night, and that if the sun were always 

 below the horizon there would be night, though 

 there had been no day. We thus know from 

 experience that the succession of night and day 

 is not unconditional. Let me add, that the ante- 

 cedent which is only conditionally invariable is 

 not the invariable antecedent. Though a fact 

 may, in experience, have always been followed 

 by another fact, yet if the remainder of our 

 experience teaches us that it might not always 

 be so followed, or if the experience itself is such 

 as leaves room for a possibility that the known 

 cases may not correctly represent all possible 



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