Ambrus, Attila2009-08-072009Ambrus, Attila. 2009. Theories of coalitional rationality. Journal of Economic Theory 144(2): 676-695.0022-0531http://nrs.harvard.edu/urn-3:HUL.InstRepos:3204917This paper generalizes the concept of best response to coalitions of players and offers epistemic definitions of coalitional rationalizability in normal form games. The (best) response of a coalition is defined to be an operator from sets of conjectures to sets of strategies. A strategy is epistemic coalitionally rationalizable if it is consistent with rationality and common certainty that every coalition is rational. A characterization of this solution set is provided for operators satisfying four basic properties. Special attention is devoted to an operator that leads to a solution concept that is generically equivalent to the iteratively defined concept of coalitional rationalizability.en-USepistemic foundations of solution conceptscoordinationcoalitional agreementsnormal form gamesJournal Article10.1016/j.jet.2007.03.010