Introduction.- Part I. The Ontology of Groups: Their Minds, Intentions, Actions and Interactions.- Chapter 1. Who is Afraid of Group Agents and Group Minds?; Raimo Tuomela.- Chapter 2. Trying to Act Together - The Structure and Role of Trust in Joint Action; Hans Bernhard Schmid.- Chapter 3. Missing the Forest for the Trees: The Theoretical Irrelevance of Shared Intentions; Kendy Hess.- Chapter 4. The Boys Carried the Piano Upstairs: Reconsidering Akratic Action in Groups; Beatrice Kobow.- Chapter 5. Creating Interpersonal Reality through Conversational Interactions; Antonella Carassa and Marco Colombetti.- Part II. Into the Background: Capacties and Cases.- Chapter 6. Social Rules and the Social Background; Michael Schmitz.- Chapter 7. Sharing the Background: Searle, Wittgenstein and Heidegger on the Background of Rule-Governed Behavior; Titus Stahl.- Chapter 8. Becoming Aware of One Another - Two Routes towards Joint Attention; Ulla Schmid.- Chapter 9. Social Ontology, Cultural Sociology, and the War on Terror: Towards a Cultural Explanation of Institutional Change; Werner Binder.- Part III. Social Reality: Its Essence and Constitution.- Chapter 10. Three Ways of Misunderstanding the Power of Rules; Olivier Morin.- Chapter 11. Arbitral Functions and Constitutive Rules; Emanuele Bottazzi and Roberto Ferrario.- Chapter 12. Social Ontology as Embedded in the Tradition of Phenomenological Realism; Alessandro Salice.- Chapter 13. Ontological Dependence and Essential Laws of Social Reality; Francesca de Vecchi.