GROUNDS OF DISBELIEF. 16& 



recondite truth, speaks ill for the state of philosophical specu- 

 lation 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 induc- 

 tion that it shall not contradict any known fact. Is it not 

 then a petitio principii to say, that the fact ought to be disbe- 

 lieved 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 ante- 

 cedent 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 

 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 observations 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 

 nature is established ; and so long as this law is received as 

 such, the assertion 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 overturn 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 

 follow, 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 infe- 



112 



