Rationality and Deceit: Why Rational Egoism Cannot Make Us Moral

Abstract

In this paper I claim that social preferences are necessary mechanisms for cooperation. Social preferences include altruistic ones, and these imply a non-instrumental interest in the welfare of other agents. This claim challenges a view common among economists and game theorists, according to which rational egoism is sufficient for cooperation and explains it in humans. Since evidence has been mounting in experimental economics that humans do have social preferences, the question arises: what does the existence of such preferences imply for the view of classical economists and game theorists? Three views are briefly described assuming that humans have been designed for cooperation because it is important for survival: (1) social preferences function as backup mechanisms in case rational egoism contingently fails; (2) cooperation is the rational move in repeated Prisoner’s Dilemmas, but rationality in humans is imperfect by design and requires the presence of social preferences to remedy human imperfection; (3) cooperation is not the rational move for rational egoists when they lack social preferences, because deceit and coercion offer better payoffs. I argue that this third view is the correct one. Morality requires a primitive disposition to take persons as equals, in order to block the use of deception as a rational option.