A representational account of mutual belief

Although the notion of common or mutual belief plays a crucial role in game theory, economics and social philosophy, no thoroughly representational account of it has yet been developed. In this paper, I propose two desiderata for such an account, namely, that it take into account the possibility of inconsistent data without portraying the human mind as logically and mathematically omniscient. I then propose a definition of mutual belief which meets these criteria. This account takes seriously the existence of computational limitations. Finally, I point out that the epistemic logic (or theory) needed to make the definition work is subject to the Kaplan/Montague Paradox of the Knower. I argue that this is not a defect of the account, and I discuss briefly the bearing of recent work on the paradox of the Liar upon this problem.Much of this work was carried out with the support of a grant from the National Science Foundation to the Center for Cognitive Science at the University of Texas at Austin (Grant No. IRI-8719064). Much thanks to Tyler Burge, Nicholas Asher, and Brian Skyrms for their criticisms and suggestions.