at least in relation to certain conditions, to put one's own will into a 'pool of wills' dedicated, as one, to a single goal (or whatever it is that the pool is dedicated to)". If two or more people have openly expressed such willingness in relation to a particular goal, in conditions of common knowledge, then the pertinent pool of wills is set up. In other words, the people concerned constitute the plural subject of the goal. As an alternative to talking of a pool of wills Gilbert refers also to joint commitment as when she writes: "the wills of the parties are jointly committed" (198). In later work she has preferred the language of joint commitment. Gilbert compares the plural subject to the singular subject and argues, with allusion to Durkheim, that "In order for individual human beings to form collectivities, they must take on a special character, a 'new' character, insofar as they need not, qua human beings, have that character. Moreover, humans must form a whole or unit of a special kind...a plural subject". In subsequent writings Gilbert has continued the development and application of her plural subject theory. Each of the essay collections Living Together (1996), Sociality and Responsibility (2000) and Marcher Ensemble (in French) (2003) is composed of relevant papers authored by Gilbert. In her book A Theory of Political Obligation (2006; 2008) Gilbert offers a new perspective on a classical problem in political philosophy, generally known as 'the' problem of political obligation. As Gilbert makes clear in her book, there are many versions of this problem. She addresses the question whether there is something about one's being the member of a particular society that means one is obligated to uphold the political institutions of that society. Unlike most contemporary writers on the subject, she does not insist that the obligation in question is a matter of moral requirement. Gilbert argues that there are obligations of a different sort, and that these that are a function of membership in a political society construed as membership in a particular kind of plural subject constituted, as are all plural subjects, by a joint commitment. Other topics Gilbert has addressed in one or more of her publications include agreements and promises, authority, collective emotions, collective responsibility, personal decisions and intentions, marital love, mutual recognition, patriotism, rights (in particular claim-rights), shared attention, shared values, social rules, and social unity.