The beliefs of ecomists are t solely determined by empirical evidence in direct relation to the theories and models they hold. Ecomists hold 'ontological presuppositions', fundamental ideas about the nature of being which direct their thinking about ecomic behaviour. In this volume, leading philosophers and ecomists examine these hidden presuppositions, searching for a 'world view' of ecomics. What properties are attributed to human individuals in ecomic theories, and which are excluded? Does ecomic man exist? Do markets have an essence? Do macroecomic aggregates exist? Is the ecomy a mechanism, the functioning of which is governed by a limited set of distinct causes? What are the methodological implications of different ontological starting points? This collection, which establishes ecomic ontology as a coordinated field of study, will be of great value to ecomists and philosophers of social sciences.