 For his part, Sidgwick at least claimed that he was part of the new movement, describing himself as a disciple of Jevons: “as Jevons had admirably explained, the variations in the relative market values of different articles express and correspond to variations in the comparative estimates formed by people in general, not of the total utilities of the amounts purchased of such articles, but of their final utilities; the utilities, that is, of the last portions purchased” (Sidgwick 1901: 82). But he did allow that the differences with the older, Millian school had been exaggerated, and he continued, despite his considerable mathematical expertise, to do economics in a qualitative mode. Even so, he showed considerable acumen in setting out and conceptually clarifying the fundamental concepts of economics (wealth, value, labor, money, efficiency, etc.), in bringing out the difficulties involved in cross-cultural and trans-historical comparisons of wealth, and in analyzing the various cases of market failure, from monopoly to collective action problems to negative externalities. Indeed, his accounts of market failure and the possible remedies—the “art” of political economy—have received somewhat more recognition. Even Marshall praised this side of Sidgwick’s work, calling the relevant section of the Principles the best thing of its kind “in any language” (Pigou 1925). It is widely admitted that Marshall’s hand-picked successor at Cambridge, A. C. Pigou, produced a form of welfare economics that largely recapitulated Sidgwick’s contributions (Backhouse 2006; Medema 2009; Cook 2009; Winch 2009; and Schultz 2017).