These original essays focus on a wide range of topics related to Frank Hahn'sdistinguished work in economics. Ranging from market analysis and game theory to the microeconomicfoundations of macroeconomics and from equilibrium and optimality with missing markets to economicsand society, they reflect the diversity of modem research in economic theory. What distinguishesHahn's work and many of the essays in this book is that the motivation often comes from practicalconcerns about unemployment, savings and investment, poverty, or the stability of markets.The essaysin Part I deal with the microeconomic foundations of macroeconomics - a field in which Hahn has madeimportant contributions, most notably in the theory of monetary economics. Topics include anevaluation of Hahn's contribution to the theory of distribution and such macroeconomic themes ascoordination failure, multiple equilibria, and strategic issues.Part II contains recentcontributions to game theory reflecting Hahn's interest in the question of what is rationalbehavior. The essays in Part III concentrate on general-equilibrium theory with missing markets, afield in which Hahn has made major advances. Although the essays address a different set of issues,they share with Hahn's works such themes as market failure, indeterminacy of equilibrium, and therole of money.Partha Dasgupta is Professor of Economics at Cambridge University. Douglas Gale isProfessor of Economics at Boston University. Oliver Hart is Professor of Economics at theMassachusetts Institute of Technology. Eric Maskin is Professor of Economics at HarvardUniversity.