This volume is the result of a conference held at the Institute for Advanced Studies, Vienna. There is still a gap reflected both in fundamental meth- odological differences and in the style of analysis between the Walrasian (and Edgeworthian) tradition of general equilibrium theory and the theo- retical and policy problems raised in the framework of Keynesian and post-Keynesian macroeconomics. The conference succeeded in bringing together economic theorists working in fields ranging from abstract prob- lems of mathematical equilibrium analysis to applied macroeconomic theory, and it is hoped that the present volume will contribute to bridging the above-mentioned hiatus. As organizer of the meeting and editor of its proceedings I want to thank the Institute for Advanced Studies for providing facilities and funds. I am also sincerely grateful to all my colleagues from the Institute for their generous help, in particular to Mrs Monika Herkner without whose assistance and organizational talent the conference would certainly not have been the success it in fact - in the opinion of all participants - turned out to have been. Furthermore, I wish to express my gratitude towards all participants in the meeting and contributors to the volume whose patient support of the whole enterprise proved indispensable. To Mrs Elfriede Auracher I am deeply indebted for her skillful and effective general management of the editorial work and her invaluable assistance in compiling the indexes.