GROUNDS OF DISBELIEF. 439 



to be disbelieved provisionally. If, however, an alleged fact be in contra- 

 diction, not to any number of approximate generalizations, but to a com- 

 pleted generalization grounded on a rigorous induction, it is said to be im- 

 possible, 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 cred- 

 ibility of miracles, excited so violent a controversy. Hume's celebrated 

 doctrine, that nothing is credible which is contradictory 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 in- 

 credible. That such a maxim as tliis should either be accounted a danger- 

 ous 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 statement 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 experi- 

 mentuni 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, tlie cause of B, or an indispensable 

 part of its cause; and if A be tried again with many totally different sets 

 of antecedents and B still follows, then it is the whole cause. If these ob- 

 servations or experiments have been repeated so often, and by so many 

 persons, as to exclude all supposition of error in the observer, a law of na- 

 ture is established ; and so long as this law is received as such, the asser- 

 tion that on any particular occasion A took place, and yet B did not follow, 

 without any counteracting cause, must be disbelieved. Such an assertion 

 is not to be credited on any less evidence than what would suffice to over- 

 turn the law. The general truths, that whatever has a beginning has a 

 cause, and that when none but the same causes exist, the same effects fol- 

 low, rest on the strongest inductive evidence possible ; the proposition that 

 things affirmed by even a crowd of respectable witnesses are true, is but an 

 approximate generalization ; and — even if we fancy we actually saw or felt 

 the fact which is in contradiction to the law — what a human being can see 

 is no more than a set of appearances; from which the real nature of the 

 phenomenon is merely an inference, and in this inference approximate gen- 

 eralizations usually have a large share. If, therefore, we make our election 

 to hold by the law, no quantity of evidence whatever ought to persuade us 

 that there has occurred any thing in contradiction to it. If, indeed, the 

 evidence produced is such that it is more likely that the set of observations 

 and experiments on which the law rests should have been inaccurately per- 

 formed or incorrectly interpreted, than that the evidence in question should 

 be false, we may believe the evidence ; but then we must abandon the law. 

 And since the law was received on what seemed a complete induction, it 

 can only be rejected on evidence equivalent; namely, as being inconsistent 

 not with any number of approximate generalizations, but with some other 



