Over the last forty years, Professor David Gale has played a leading role in developing two themes of fundamental importance to economic first, the formulation of appropriate concepts of economic equilibrium in the tradition of Walras and Cournot; second, the analysis of evolution of economic agents and institutions in a dynamic environment. As a tribute to his creative research, this volume contains contributions from leading researchers who explore different directions in these areas. Some have extended the existing literature, others have stressed the need for new directions. The volume will be of particular interest to researchers in economic theory.