Epistemic considerations of decision making in games

Abstract

From the Ex Ante point of view, an axiomatization of decision making in a game with pure strategies is given, while considering its epistemic aspects in propositional game (epistemic) logic. Our axiomatization consists of four base axioms for predicted final decisions. One of them is an epistemic requirement, which together with the others leads to an infinite regress of the knowledge of these axioms. The resulting outcome of this regress is expressed as the common knowledge of the base axioms. We give meta-theoretical evaluations of the derivation of this infinite regress, and consider its implications in solvable and unsolvable games. For a solvable game, it determines predicted decisions to be the common knowledge of a Nash equilibrium, and for an unsolvable game, it is the common knowledge of a subsolution in Nash’s sense. The latter result needs the common knowledge of the additional information of which subsolution would be played. We give also meta-theoretical evaluations of these results.