Allard Tamminga on Collective Obligations and Joint Plans

Allard Tamminga (University of Groningen), gave a lecture entitled "Collective Obligations and Joint Plans" at the "Formal philosophy" seminar on March 24.

Abstract:  We study relations between collective obligations, member obligations and individual obligations. Anindividual obligation is what an individual ought to do irrespective of the collective obligations of the groups of which this individual is a member. We say that an individual agent fulfills her individual obligation if and only if she performs one of her optimal individual actions. Likewise, a group fulfills its collective obligation if and only if it performs one of its optimal group actions. A member obligation is what an individual group member ought to do in order to ensure that the group itself fulfills its collective obligation. Member obligations are generated by a joint plan that specifies for every group member which individual actions may be performed. Technically, the public acceptance of a joint plan updates the deontic ideality of the action profiles in a coordination game. We show that if a coordination game is updated with a good plan (in a sense to be specified below), then for every individual member of the collective it holds that an individual action is allowed by a joint plan if and only if that individual action is optimal for that individual in the coordination game that results from updating the original coordination game with the joint plan. We thus establish a strong relation between collective rationality and individual rationality.