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 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 incredible."(1) He then proceeds to meet possible objections: "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 should not contradict any known fact. Is it not, then, a _petitio principii_ to say, that the fact ought to be disbelieved because the induction 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 cruris_." It will be remarked that Dr. Farrar adopts Mr. Mill's phraseology in one of the above questions to affirm the reverse of his opinion. Mr. Mill decides that the proposition is not a _petitio principii_; Dr. Farrar says, as in continuation of his reference to Mr. Mill, that it is a flagrant _petitio principii_. Mr. Mill proceeds to prove his statement, and he naturally argues that, if observations or experiments have been repeated so often, and by so many persons, as to exclude all supposition of {81}