In the 1970s, the Keynesian orthodoxy in macroeconomics began to break down. In direct contrast to Keynesian recommendations of discretionary policy, models advocating laissez-faire came to the forefront of economic theory. Laissez-faire no longer stood as an exceptional policy endorsed for rare occurrences of market clearing; rather it became the policy standard. This book provides the definitive account of this watershed and traces the evolution of laissez-faire using the cases of its proponents, Frank Knight, Henry Simons, Friedrich von Hayek, Milton Friedman, James Buchanan and Robert Lucas. By elucidating the pre-analytical framework of their writings, Sherryl Kasper accounts for the ideological influence of these pioneers on theoretical work, and illustrates that they played a primary role in founding the theoretical and philosophical use of rules as the basis of macroeconomic policy. A case study of the way in which interwar pluralism transcended to postwar neoclassicism is also featured. The volume concludes that economists ultimately favoured new classical economics due to the theoretical developments it incorporated, although at the same time, since Lucas uncritically adapted some of the ideas and tools of Friedman, an avenue for ideological influence remained. Tracing the evolution of American macroeconomic theory from the 1930s to the 1980s, this book will appeal to those with an interest in macroeconomics and in the history of scholars associated with the Chicago School of economics.