Debates around the assumption of rationality in economic theory abound and are too numerous to be listed here. Traditionally, rationality of a decision maker is captured by a set of (testable) axioms, whose meaning and strength can be discussed. These rationality axioms however do not all have the same status in the sense that they bear on different things. One could actually distinguish three ...

Arrow’s impossibility theorem states that if a collective choice rule satisfies unrestricted domain, weak Pareto, independence of irrelevant alternatives, and collective rationality, then there exists a dictator. Among others, Arrow’s postulate of collective rationality is controversial. We propose a new axiom for a collective choice rule, decisiveness coherence, which is weaker than collective...

The paper discusses rationality at two levels. According to a common opinion the key to rationality at the group level is a willingness to contribute unselfishly at the individual level. I claim that even when rationality at the individual level is denied, it is often achieved by social punishment. The difficulty to organize a social project is exaggerated. The relative ease of implementing ind...

Bounded rationality has often been invoked in the theory of economic organization, mainly to rationalize contractual incompleteness. I argue that one may distinguish between " thin " and " thick " notions of bounded rationality; that models that rely on thin notions are often effectively indistinguishable from models that rely on full rationality; and that the value-added in terms of economic c...

Rational requirements have a special status in the theory of rationality. This is obvious in one sense: they supply the content of that theory. But I want to suggest that rational requirements have another special status—as objects of the theory of rationality. In slogan form, my thesis is: Fixed Point Thesis: Mistakes about the requirements of rationality are mistakes of rationality. The key c...