Date of Completion


Embargo Period



Margaret Gilbert, joint commitment, social epistemology, collective intentionality, group belief

Major Advisor

Michael Lynch

Associate Advisor

Donald Baxter

Associate Advisor

Austen Clark

Field of Study



Doctor of Philosophy

Open Access

Open Access


We often credit groups with reasoning well. Juries can be diligent, or committees negligent. We even credit the groups independently of crediting the members. But what are groups? How can they form beliefs, and how are those beliefs epistemically evaluated? This dissertation aims to answer these questions.

The first chapter addresses a question about shared action. What does it take for some people to do something together, as a group? I defend a view based on Margaret Gilbert’s work, where joint commitment is the basic building block of togetherness. Joint commitments are directive-like representations which people direct towards themselves and others, and which they take up from themselves and others. This view avoids the problems typically attributed to Gilbert’s account while capturing its virtues.

In the second chapter, I address metaphysical worries about plural subjects, or jointly-committed people. One concern is that groups are entities “over and above” their members (a view which some have endorsed). I develop a broadly reductionist theory about group ontology, where facts about group persistence are replaced with facts about the history of joint commitments. This captures the sense in which groups are nothing but their members, even though there is more to groups than facts about their members.

The third chapter explains group belief, and why it matters. The view developed here largely follows Gilbert’s own theory, that group belief is a joint commitment phenomenon. However, the view that groups establish their beliefs by jointly committing to beliefs via negotiation has drawn serious criticisms, which I answer here.

Finally, the fourth chapter develops a virtue-theoretic account of epistemic evaluation for group beliefs. Since we often credit groups for their epistemic responsibility, I apply the theories which take epistemic responsibly seriously – namely, virtue responsibilist theories – to group belief. What results is an account of group virtue, where well-formed beliefs flow from joint attitudes of the sort constitutive of virtue. The overall view takes joint commitment to be central at every stage of analysis: central to groups, central to their beliefs, and central to their epistemic agency