, Volume 27, Issue 1–2, pp 29–39 | Cite as

Common Knowledge and Convention

  • Giacomo SillariEmail author


This paper investigates the epistemic assumptions that David Lewis makes in his account of social conventions. In particular, I focus on the assumption that the agents have common knowledge of the convention to which they are parties. While evolutionary analyses show that the common knowledge assumption is unnecessary in certain classes of games, Lewis’ original account (and, more recently, Cubitt and Sugden’s reconstruction) stresses the importance of including it in the definition of convention. I discuss arguments pro et contra to argue that, although the assumption might be relevant to a descriptively adequate account of social convention, it is not required for its rational reconstruction. I then point out that Lewis’ account, properly speaking, is of common reason to believe, rather than of common knowledge, and argue that, in order to formalize aptly the distinction between reason to believe and belief, standard formal epistemic models need to be supplemented with so-called awareness structures. Finally, I stress that the notion of knowledge implicit in Lewis’ text involves interesting elements that cannot be captured in the standard propositional formalizations, but need the full expressive force of quantified epistemic logic.


David Lewis Convention Common knowledge Awareness Quantified epistemic logic 



The author wishes to thank Cristina Bicchieri, Ken Binmore, Margaret Gilbert, Herbert Gintis, Luca Tummolini, Peter Vanderschraaf and two anonymous referees for valuable comments, suggestions and criticisms.


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Philosophy, Politics and Economics ProgramUniversity of PennsylvaniaPhiladelphiaUSA

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