 I start by discussing the criterion of prediction. Hypotheses ought to foretell phenomena, “at least all phenomena of the same kind,” Whewell explained, because “our assent to the hypothesis implies that it is held to be true of all particular instances. That these cases belong to past or to future times, that they have or have not already occurred, makes no difference in the applicability of the rule to them. Because the rule prevails, it includes all cases” (1858b, 86). Whewell’s point here is simply that since our hypotheses are in universal form, a true hypothesis will cover all particular instances of the rule, including past, present, and future cases. But he also makes the stronger claim that successful predictions of unknown facts provide greater confirmatory value than explanations of already-known facts. Thus he held the historical claim that “new evidence” is more valuable than “old evidence.” He believed that “to predict unknown facts found afterwards to be true is … a confirmation of a theory which in impressiveness and value goes beyond any explanation of known facts” (1857/1873, II, 557). Whewell claimed that the agreement of the prediction with what occurs (i.e., the fact that the prediction turns out to be correct), is “nothing strange, if the theory be true, but quite unaccountable, if it be not” (1860a, 273–4). For example, if Newtonian theory were not true, he argued, the fact that from the theory we could correctly predict the existence, location and mass of a new planet, Neptune (as did happen in 1846), would be bewildering, and indeed miraculous.