  Lewis requires that a convention be one among several possible alternatives. Even if one follows Miller in rejecting that requirement, it seems clear that there are many cases, such as the choice of monetary currency, where we must select from among numerous candidate conventions. This raises the question of how we select a particular candidate. An analogous question arises for game theory more generally, since a game may have many Nash equilibria. It is rational to play my part in a Nash equilibrium, if I believe that other agents will play their parts. But why should I believe that others will play their parts in this particular equilibrium? If we assume that players cannot engage in pre-game communication, three basic answers suggest themselves: players converge upon a unique equilibrium through rational reflection on the logic of their strategic situation; or they are guided by psychological factors outside the ambit of purely rational analysis; or they learn from prior experience which equilibrium to choose. One might also combine these three suggestions with one another.