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...

If we take it that, at least in the social sciences, "realistic" implies "finite", then countless economic models involving infinitary assumptions must obviously be classified as unrealistic - for example, models with infinitely divisible goods, a continuum of traders, consumers optimizing over...