ABSTRACT
In seeking the postulate or postulates required to make inductive probabilities approach certainty as a limit, there are two desiderata. On the one hand, the postulate or postulates must be sufficient, from a purely logical point of view, to do the work that is asked of them. On the other hand—and this is the more difficult requirement—they must be such that some inferences which depend upon them for their validity are, to common sense, more or less unquestionable. For example: you find two verbally identical copies of the same book, and you assume unhesitatingly that they have a common causal antecedent. In such a case, though every one will admit the inference, the principle which justifies it is obscure, and is only to be discovered by careful analysis. I do not demand that a general postulate arrived at by this method should itself possess any degree of self-evidence, but I do demand that some inferences which, logically, depend upon it, shall be such as any person who understands them, except a sceptical philosopher, will consider so obvious as to be scarcely worth stating. There must, of course, be no positive grounds for regarding a suggested postulate as false. In particular, it should be self-confirmatory, not self-refuting, i.e. inductions which assume it should have conclusions consistent with it.
