Helping somebody may undermine his incentives to work. What Buchanan identified more than 25 years ago as the Samaritan's dilemma is basically a time-inconsistency problem. The paper discusses possible solutions of the dilemma such as punishment within an iterated game, reshaping the game in the...

In evolutionary models of indirect reciprocity, reputation mechanisms can stabilize cooperation even in severe cooperation problems like the prisoner's dilemma. Under certain circumstances, conditionally cooperative strategies, which cooperate iff their partner has a good reputation, cannot be...