While standard accounts of the theoretical debates in 1930s economic thought invariably pit John Maynard Keynes against Friedrich von Hayek, this reflexive dichotomy is in many respects exceedingly superficial. It is the argument of this book that both Keynes and Hayek developed their respective theories of the business cycle within the tradition of Swedish economist Knut Wicksell, and that this shared genealogy manifested itself in significant theoretical affinities between the two apparent antagonists. The salient features of Wicksell’s work, namely, the importance of money, the role of uncertainty, coordination failures, and the element of time in capital accumulation, all motivate the Keynesian and Hayekian theories of economic fluctuations, and contributed, The author argues to a fundamental convergence between the two economists during the course of the 1930s. Moreover, this shared, “Wicksellian” vision of the economic problem points to a very different research agenda from that of the Walrasian-style, general equilibrium analysis that has dominated postwar macroeconomics. The book aims not only to deconstruct some of the historical misconceptions of the Keynes versus Hayek debate but also to suggest how the insights thus uncovered can inform and instruct modern theory. While much of the analysis is quite technical, it does not assume previous knowledge of 1930s economic theory and thus should be accessible to economists, political scientists, and historians with general economics training, as well as to graduate students in these fields.