Margaret Gilbert

This article explores the question: what is it for two or more people to intend to do something in the future? In a technical phrase, what is it for people to share an intention ? Extending and refining earlier work of the author’s, it argues for three criteria of adequacy for an account of shared intention (the disjunction, concurrence, and obligation criteria) and offers an account that satisfies them. According to this account, in technical terms explained in the paper, people share an intention when and only when they are jointly committed to intend as a body to do such-and-such in the future. This account is compared and contrasted with the common approach that treats shared intention as a matter of personal intentions, with particular reference to the work of Michael Bratman.

Does one have special obligations to support the political institutions of one’s own country precisely because it is one’s own? In short, does one have political obligations? This book argues for an affirmative answer, construing one’s country as a political society of which one is a member, and a political society as a special type of social group. The obligations in question are not moral requirements derived from general moral principles. They come, rather, from one’s participation in a special kind of commitment: a joint commitment. This theory is referred to as the plural subject theory of political obligation since, by the author’s definition, those who are party to any joint commitment constitute a plural subject of some action in a broad sense of the term. Several alternative theories are compared and contrasted with plural subject theory, with a particular focus on the most famous — actual contract theory — according to which membership in a political society is a matter of participation in an agreement. The book offers plural subject accounts of both social rules and everyday agreements, and includes discussion of political authority and punishment.

Philosophers using game-theoretical models of human interactions have, I argue, often overestimated what sheer rationality can achieve. (References are made to David Gauthier, David Lewis, and others.) In particular I argue that in coordination problems rational agents will not necessarily reach a unique outcome that is most preferred by all, nor a unique 'coordination equilibrium' (Lewis), nor a unique Nash equilibrium. Nor are things helped by the addition of a successful precedent, or by common knowledge of generally accepted personal principles. Commitments like those generated by agreements may be necessary for rational expectations to arise. Social conventions, construed as group principles (following the analysis in my book On Social Facts), would suffice for this task.

What is it for a group to believe something? A summative account assumes that for a group to believe that p most members of the group must believe that p. Accounts of this type are commonly proposed in interpretation of everyday ascriptions of beliefs to groups. I argue that a nonsummative account corresponds better to our unexamined understanding of such ascriptions. In particular I propose what I refer to as the joint acceptance model of group belief. I argue that group beliefs according to the joint acceptance model are important phenomena whose aetiology and development require investigation. There is an analogous phenomenon of social or group preference, which social choice theory tends to ignore.