This paper introduces the concept of impartial, non-utility based morality to the theory of non-cooperative games. In non-cooperative games, the mathematical description of a game requires a set of players, the strategy set of each player, and a payoff function mapping each strategy combination into the real number space. Behavioural economics broadened the preference domain, thereby changing, for an arbitrarily strong concern to social motives, the value that a payoff function assigns to a given strategy combination for a socially-oriented player. By contrast, the methodology I propose adds an impartial moral judgment function, mapping each strategy combination to the real number space, to the previous paradigm. Using this function I can partition the set of strategies for each individual into morally 'acceptable' and morally 'prohibitive' subsets of strategies. Building on this terminology, I formally define the main concept of the new methodology (Moral Rule) and present best response functions for two moral rules based on moral philosophy. Furthermore, I present some examples to show how the new methodology can be applied to characteristic games used in the literature and end up by discussing the motivation for the new theory, its roots in moral philosophy, psychology, and neuroscience, and its main departures from the classical approach.
[Manuscript in preparation]