 There was in the eighteenth and nineteenth centuries a passionate debate about scientific method—at stake was the ‘method of hypothesis’ which postulated hypotheses about unobservable entities which ‘saved the phenomena’ and thus were arguably true (see Laudan 1981a). Critics of this method pointed out that hypotheses could always be adjusted artificially to accommodate any amount of data. But it was noted that some such theories had the further virtue of generating specific predictions of heretofore unobserved phenomena—thus scientists like John Herschel and William Whewell argued that hypotheses that saved phenomena could be justified when they were confirmed by such ‘novel’ phenomena. Whewell maintained that predictions carry special weight because a theory that correctly predicts a surprising result cannot have done so by chance, and thus must be true (Whewell 1849 [1968: 294]). It thus appeared that predicted evidence confirmed theory more strongly than accommodated evidence. But John Stuart Mill (in his debate with Whewell) categorically denied this claim, affirming that 