Group deliberation is a discursive process whereby participants seek to reach understanding by exchanging considerations, aiming to build consensus for the purpose of action-coordination. My PhD thesis develops formal (mathematical) models to study the mechanics of group deliberation. In this talk, I first address the question of whether formal models are appropriate to study group deliberation in the first place. On Jürgen Habermas' influential theory of communicative action, formal models are inappropriate to study processes of communicative action (such as deliberation), because they model agents as engaging in purposive strategic action, rather than as acting so as to reach understanding. I develop a concept, deliberative strategic action, and argue that it provides a conceptual warrant to study deliberation using formal models. An agent engaged in deliberative strategic action relies on purposive rationality to carry out a plan of action for the end of reaching understanding. Second, I present a framework, objects of deliberation. Here, deliberating agents seek consensus on one or more parts of a hypothetical imperative: ends, means, or facts. I argue that this framework helps us make sense of the diversity of formal models of deliberation.
