314 INDUCTION. 



cumstances were repeated, it would occur again ; and not only if all, 

 but there is some particular portion of those circumstances upon which 

 the phenomenon is invariably consequent. With most of them, how- 

 ever, it is not connected in any peiTnanent manner : its conjmiction 

 with those is said to be the effect of chance, to be merely casual. 

 Facts casually conjoined are separately the effects of causes, and 

 therefore of laws; but of different causes, and causes not connected 

 by any law. 



It is incorrect, then, to say that any phenomenon is produced by 

 chance ; but we may say that two or more phenomena are conjoined 

 by chance, that they coexist or succeed one anotlier only by chance j 

 meaning that they are in no way related through causation ; that they ai'e 

 neither cause and effect, nor effects of the same cause, nor effects of 

 causes between which there subsists any law of coexistence, nor even 

 effects of the same original collocation of piimeval causes. 



If the same casual coincidence never occurred a second time, we 

 should have an easy test for distinguishing such from the coincidences 

 which are results of a law. As long as the phenomena had been found 

 together only once, so long, unless we knew some more general laws 

 from which the coincidence might have resulted, we could not distin- 

 guish it from a casual one ; but if it occurred twice, we should know 

 that the phenomena so conjoined must be in some way connected 

 through their causes. 



There is, however, no such test. A coincidence may occur again 

 and again, and yet be only casual. Nay, it would be inconsistent with 

 what we know of the order of nature, to doubt that every casual coin- 

 cidence will sooner or later be repeated, as long as the phenomena 

 between which it occurred do not cease to exist, or to be produced. 

 The recurrence, therefore, of the same coincidence more than once, 

 or even its fi-equent recurrence, does not prove that it is an instance of 

 any law ; does not prove that it is not casual, or, in common language, 

 the effect of chance. 



And yet, when a coincidence cannot be deduced fi'om knowni laws, 

 nor proved by experiment to be itself a case of causation, the fi-equency 

 of its occurrence is the only evidence fi'om which we can infer that.it 

 is the result of a law. Not, however, its absolute fi-equency. The 

 question is not whether the coincidence occurs often or seldom, in the 

 ordinary sense 'of those terms ; but whether it occurs 7fiore often than 

 chance will account for; more often than might rationally be expected 

 if the coincidence were casual. We have to decide, therefore, what 

 degi'ee of frequency in a coincidence chance will account for. And to 

 this there can be no general answer. We can only state the piinciple 

 by which the answer must be deteiiained : the answer itself will be 

 different in every different case. 



^ Suppose that one of the phenomena, A, exists always, and the other 

 phenomenon, B, only occasionally : it follows that every instance of B 

 will be an instance of its coincidence with A, and yet the coincidence 

 will be merely casual, not the result of any connexion between them. 

 The fixed stars have been constantly in existence since the beginning 

 of human experience, and all phenomena that have come under human 

 observation have, in every single instance, coexisted with them ; yet 

 this coincidence, although equally, invariable with that which exists 

 between any of those phenomena and its ovni cause, does not prove 



