Collective Intentionality is a relatively new label for a basic social fact: the sharing of attitudes such as intentions, beliefs and emotions. This volume contributes to current research on collective intentionality by pursuing three aims. First, some of the main conceptual problems in the received literature are introduced, and a number of new insights into basic questions in the philosophy of collective intentionality are developed (part 1). Second, examples are given for the use of the analysis of collective intentionality in the theory and philosophy of the social sciences (part 2). Third, it is shown that this line of research opens up new perspectives on classical topics in the history of social philosophy and social science, and that, conversely, an inquiry into the history of ideas can lead to further refinement of our conceptual tools in the analysis of collective intentionality (part 3).