Games theory is that branch of mathematics studying situations where the agents (players) must face some choices. Depending on all players' choices each player has an utility. The set of choices taken by a player constitutes his strategy.

Games theory tries to find good strategies (that is, pursuing some notion of equilibrium) and to explain some social behaviours of the real life. The most commonly-used notion of equilibrium is the Nash equilibrium. It gives an intuition about what people do, it explains some behaviour, but it does not tollerate "faulty" or "unexpected" behaviour, it does not deal with coalitions, it does not take computational aspects into account, and it does not deal with cases where the players are not aware of all aspects of the game. Here, I perform an epistemological analysis about game theory and Nash equilibrium.