SECT. 10.] The Rule of Succession. 201 



to pronounce that any line of enquiry is impossible ; but 

 the difficulties would certainly be enormous. And interesting 

 as the facts would be, supposing that we had succeeded 

 in securing them, they would not be of the slightest im 

 portance in Logic. However the question were settled : 

 whether, for instance, we proved that the sentiment or 

 emotion of belief grew up slowly and gradually from a sort 

 of zero point under the impress of repetition of experience ; 

 or whether we proved that a single occurrence produced 

 complete belief in the repetition of the event, so that 

 experience gradually untaught us and weakened our con 

 victions ; in no case would the mature mind gain any aid 

 as to what it ought to believe. 



I cannot but think that some such view as this must 

 occasionally underlie the acceptance which this rule has re 

 ceived. For instance, Laplace, though unhesitatingly adopt 

 ing it as a real, that is, objective rule of inference, has gone 

 into so much physiological and psychological matter towards 

 the end of his discussion (Essai philosophique) as to suggest 

 that what he had in view was the natural history of belief 

 rather than its subsequent justification. 



Again, the curious doctrine adopted by Jevons, that the 

 principles of Induction rest entirely upon the theory of 

 Probability, a very different doctrine from that which is 

 conveyed by saying that all knowledge of facts is probable 

 only, i.e. not necessary, seems unintelligible except on some 

 such interpretation. We shall have more to say on this 

 subject in our next chapter. It will be enough here to 

 remark that in our present reflective and rational stage 

 we find that every inference in Probability involves some 

 appeal to, or support from, Induction, but that it is im 

 possible to base either upon the other. However far back 

 we try to push our way, and however disposed we might be 



