We introduce a new understanding of deontic modals that we callobligations as weakest permissions. We argue for its philosophical plausibility, study its expressive power in neighborhood models, provide a complete Hilbert-style axiom system for it and show that it can be extended and applied to practical norms in decision and game theory.

David Lewis is widely regarded as the philosopher who introduced the concept of common knowledge. His account of common knowledge differs greatly from most later accounts in philosophy and economy, with the central notion of his theory being ‘having reason to believe’ rather than ‘knowledge’. Unfortunately, Lewis’s account is rather informal, and the argument has a few gaps. This paper assesses two major attempts to formalise Lewis’s account and argues that these formalisations are missing a crucial aspect of this account. (...) Therefore, a new reconstruction is proposed, which explicitly discusses ‘reasons’ and uses a logic inspired by justification logic. (shrink)

:Most game-theoretic accounts of institutions reduce institutions to behavioural patterns the players are incentivized to implement. An alternative account linking institutions to rule-following behaviour in a game-theoretic framework is developed on the basis of David Lewis’s and Ludwig Wittgenstein's respective accounts of conventions and language games. Institutions are formalized as epistemic games where the players share some forms of practical reasoning. An institution is a rule-governed game satisfying three conditions: common understanding, minimal awareness and minimal practical rationality. Common understanding has (...) a strong similarity with Ludwig Wittgenstein's concept of lebensform while minimal awareness and minimal practical rationality capture the idea that rule-following is community-based. (shrink)

This paper examines the perceptual and reasoning processes that underpin regularities in behaviour. A distinction is made between situations as they are, or as described by an omniscient external observer, and situations as agents see or frame them. Different frames can stem from differences in culture, experience and personality, as well as from other context-specific factors. Drawing upon David Lewis’sConvention(1969), I show that consistency between reasoning and experience does not preclude individuals from understanding the same state of affairs differently, and (...) that agents’ beliefs about others’ beliefs may well be wrong. As a result, cases may occur in which conventions are sustained by false but mutually consistent and self-confirming beliefs. (shrink)

En 1975, David Gauthier a discuté la question desjeux de coordination purede Schelling et desjeux Hi-Lode Hodgson. Tout en proposant une analyse originale de la façon dont les joueurs rationnels se coordonnent sur des «points focaux», Gauthier a soutenu contre Schelling et Hodgson que dans ces jeux, une coordination réussie ne dépend pas de déviations par rapport aux principes conventionnels du choix rationnel individuel. J’avance que l’analyse de la maximisation contrainte proposée par Gauthier dansMorals by Agreement, qui s’éloigne de façon (...) notoire de la théorie des jeux conventionnelle, présente d’importantes similarités avec les analyses de la coordination de Schelling et Hodgson. La maximisation contrainte peut être envisagée comme une variante pragmatique et contractualiste de l’approche du raisonnement par équipe introduite par Hodgson. (shrink)

IntroductionA quick glance at the opening paragraphs in many of the classic logic textbooks reveals a common view: Logical methods highlight the reasoning patterns of a single agent engaged in some form of mathematical thinking.A sampling from my bookshelf: Shoenfield’s Mathematical Logic: “Logic is the study of reasoning; and mathematical logic is the study of the type of reasoning done by mathematicians”; Enderton’s A Mathematical Introduction of Logic: “Symbolic logic is a mathematical model of deductive thought”; and Chiswell and Hodges (...) Mathematical Logic: “In this course we shall study some ways of proving statements.” However, this traditional view of the “subject matter” of logic is expanding. There is a growing literature using phrases such as “rational interaction” or “information flow” to describe its subject matter while still employing traditional logical methods. The clearest example of this can be found in the work of Johan van Benthem and others on l .. (shrink)