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...

David Lewis (1974, 1994/1999) proposed to reduce the facts about mental representation sensory evidence, dispositions act, and rationality. Recently, Robert Williams (2020) Adam Pautz (2021) have taken up developed Lewis's project in sophisticated novel ways. In this paper, we aim present, clarify, ultimately object core thesis that they all build their own views around. The different developme...