Economists increasingly recognise that engagement with social ontology – the study of the basic subject matter and constitution of social reality - can facilitate more relevant analysis. This growing recognition amongst economists of the importance of social ontology is due very considerably to the work of members of the Cambridge Social Ontology Group. This volume brings together important papers by members of this group, some previously unpublished, in a collection that reveals the breadth and vitality of this Cambridge project. It provides a brilliant introduction to the central themes explored, perspectives sustained, insights achieved and how the project is moving forward.