Abstract
In this paper, we study the impact of altruism on an interaction between a samaritan and a recipient/parasite in the frame of Buchanan's samaritan's dilemma (1975). We show that, as soon as altruism reaches a certain threshold, the equilibrium of the game corresponds to the situation Buchanan called a samaritan's dilemma. We also show that the Nash equilibrium reached for these levels of altruism is a Pareto-efficient outcome. Thus, the situation Buchanan characterized as a samaritan's dilemma is not a dilemma at all. Both players are satisfied with the situation as it is and need each other, up to the point of giving birth to a sado-masochistic equilibrium. We also show that this result holds if and only if the constitutional rules are given-either the ethical rules followed by the individuals, or the form of the game. This equilibrium could be avoided if the players adopted a constitutional perspective on the situation.