188 INDUCTION. 



may draw an inference as to the antecedent improba- 

 bility of their having been present in any particular 

 case. And neither in respect to known nor unknown 

 causes are we required to pronounce upon the pro- 

 bability of their existing in nature, but only of their 

 having existed at the precise time and place at which 

 the transaction is alleged to have happened. We are 

 seldom, therefore, without the means (when the cir- 

 cumstances of the case are at all known to us) of 

 judging how far it is likely that such a cause should 

 have existed at that time and place without manifest- 

 ing its presence by some other marks, and (in the 

 case of an unknown cause) without having hitherto 

 manifested its existence in any other instance. Ac- 

 cording as this circumstance or the falsity of the 

 testimony appears more improbable, that is, conflicts 

 with an approximate generalization of a higher order, 

 we believe the testimony, or disbelieve it ; with a 

 stronger or a weaker degree of conviction, according 

 to the preponderance: at least until we have sifted 

 the matter further. 



So much, then, for the case in which the alleged 

 fact conflicts, or appears to conflict, with a real law of 

 causation. But a more common case, perhaps, is 

 that of its conflicting with uniformities of mere co- 

 existence, not proved to be dependent on causation: in 

 other words, with the properties of Kinds. It is with 

 these uniformities principally, that the marvellous 

 stories related by travellers are apt to be at variance : 

 as of men with tails, or with wings, and (until con- 

 firmed by experience) of flying fish ; or of ice, in the 

 celebrated anecdote of the Dutch travellers and the 

 King of Siam. Facts of this description, facts previ- 

 ously unheard of, but which could not from any 

 known law of causation be pronounced impossible, 



