The volume includes essays that address the philosophical issues raised in computer support of collaborative learning and by the concept of group cognition. In particular, philosophy of group cognition should tackle the following questions: * What is the nature of group cognition? * What are the conditions of possibility for the existence of group cognition? The essays explore intersubjectivity, joint attention, common ground, collaborative learning and related concepts through analysis of empirical examples and review of the most important philosophic sources.