In 1950, Armen Alchian published his paper "Uncertainty, Evolution and Economic Theory" (reprinted in this volume), a paper of striking originality, whose importance was immediately perceived and which gained him international recognition. It was clear that economics had a new master. Alchian has made important contributions to the economic analysis of inflation and unemployment and to the theory of costs and of the firm. He has played the leading role in the development of a theory of property rights. His writing is distinguished by his ability to disentangle the essential from the trivial and, above all, by his skill in showing how the same basic economic forces are at work in a wide variety of apparently completely different social settings. Armen A. Alchian is Professor Emeritus of Economics at UCLA. Ronald H. Coase is Professor Emeritus at the University of Chicago Law School. He was awarded the 1991 Nobel Prize in Economics.