SECT. 14.] Credibility of Extraordinary Stories. 419 



writers in order to extricate us from the difficulty. The con 

 troversy about miracles has probably been the most fertile 

 occasion for suggestions of this kind on one side or the 

 other. It is to this controversy, presumably, that the phrase 

 is due, so often employed in discussions upon similar sub 

 jects, a contest of opposite improbabilities. What is meant 

 by such an expression is clearly this: that in forming a 

 judgment upon the truth of certain assertions we may find 

 that they are comprised in two very distinct classes, so that, 

 according as we regarded them as belonging to one or the 

 other of these distinct classes, our opinion as to their truth 

 would be very different. Such an assertion belongs to one 

 class, of course, by its being a statement of a particular 

 witness, or kind of witness ; it belongs to the other by its 

 being a particular kind of story, one of what is called an 

 improbable nature. Its belonging to the former class is so 

 far favourable to its truth, its belonging to the latter is so far 

 hostile to its truth. It seems to be assumed, in speaking of 

 a contest of opposite improbabilities, that when these different 

 sources of conviction co-exist together, they would each in 

 some way retain their probative force so as to produce a 

 contest, ending generally in a victory to one or other of 

 them. Hume, for instance, speaks of our deducting one 

 probability from the other, and apportioning our belief to 

 the remainder 1 . Thomson, in his Laws of Thought, speaks 

 of one probability as entirely superseding the other. 



14. It does not appear to me that the slightest philoso 

 phical value can be attached to any such rules as these. 

 They doubtless may, and indeed will, hold in individual 



1 &quot;When therefore these two opinion, either on one side or the 



kinds of experience are contrary, we other, with that assurance which 



have nothing to do but subtract the arises from the remainder.&quot; (Essay 



one from the other, and embrace an on Miracles.) 



272 



