Rather less than a century ago Morelli began a revolution in art-historical method by demonstrating that every painter has his formulae for rendering details—ears, eyes, hands, drapery-folds and so on—amounting to a personal system; and that, for attribution, a study of these minutiae affords a valuable check on, if not a sounder basis than, a general sense of style; or rather that the two together form the only sound basis. There is no rule of thumb. Formulae are the artist's servants, not his masters. They appear and vanish, change and merge, according to the development of his technique and style, the influences he undergoes, the speed at which he is working, all the circumstances of his art; but in much of any painter's work they will be found recurring; rarely, as a system, in another's. Morellian method can only be effectively used by one who, like Morelli himself, is sensitive to works of art not only as aesthetic achievements but as expressions of personality; but without the tools of his forging it is impossible for sensitivity alone to make much headway. The study of Italian painting before Morelli was a chaos of unchecked traditions and conflicting hunches. Despite fine work by Hartwig, Furtwängler and others, the study of red-figure vase-painting remained much the same (without the traditions) until Beazley brought to it a rare combination of sensitivity to personal artistic style with Morellian discipline.