This collection of essays presents a sampling of the significant contributions to twentieth-century economic thought and practice by Nobel Prize-winner Milton Friedman. Friedman is widely regarded as the leader of the Chicago school of economics, which stresses the importance of the quantity of money as an instrument of governmental policy and as a major determinant of business cycles and inflation. Making an early impact on the economics profession was his analysis of economics as an empirical science, and in particular, his conclusion that the only relevant test of the acceptability of economic hypotheses is the conformity of the predictions they generate with observation. His permanent income theory of consumption, his restatement of the quantity theory of money, and his hypothesis of natural rate of unemployment has by now become part of received economic doctrine. Outside the economic profession, Friedman is best known for his outspoken statements on public policy, particularly his consistent belief that a free-enterprise system with minimum governmental intervention in the economic process will best preserve and extend both human freedom and economic prosperity. A number of the essays reprinted here are eloquent expressions of his commitment to everyone's freedom to choose.