GROUNDS OF DISBELIEF. 183 



completed generalization grounded upon a rigorous 

 induction, it is said to be impossible, and is to be 

 disbelieved totally. 



This last principle, simple and evident as it appears, 

 is the doctrine which, on the occasion of an attempt to 

 apply it to the question of the credibility of miracles, 

 excited so violent a controversy. Hume's celebrated 

 principle, that nothing is credible which is contradic- 

 tory to experience, or at variance with laws of nature, 

 is merely this very plain and harmless proposition, 

 that whatever is contradictory to a complete induction 

 is incredible. That such a maxim as this should 

 either be accounted a dangerous heresy, or mistaken 

 for a great and recondite truth, speaks ill for the state 

 of philosophical speculation on such subjects. 



But does not (it may be asked) the very state- 

 ment of the proposition imply a contradiction ? An 

 alleged fact, according to this theory, is not to be 

 believed if it contradict a complete induction. But 

 it is essential to the completeness of an induction that 

 it shall not contradict any known fact. Is it not 

 then a petitio principii to say, that the fact ought to 

 be disbelieved because the induction opposed to it is 

 complete ? How can we have a right to declare the 

 induction complete, while facts, supported by credible 

 evidence, present themselves in opposition to it ? 



I answer, we have that right whenever the 

 scientific canons of induction give it to us ; that is, 

 whenever the induction can be complete. We have 

 it, for example, in a case of causation in which there 

 has been an experimentum crucis. If an antecedent A, 

 superadded to a set of antecedents in all other respects 

 unaltered, is followed by an effect B which did not 

 exist before, A is, in that instance at least, the cause 

 of B, or a necessary part of that cause ; and if A be 



