Journal of Philosophical Logic

, Volume 38, Issue 2, pp 179–227 | Cite as

Inexact Knowledge with Introspection

  • Denis Bonnay
  • Paul Égré


Standard Kripke models are inadequate to model situations of inexact knowledge with introspection, since positive and negative introspection force the relation of epistemic indiscernibility to be transitive and euclidean. Correlatively, Williamson’s margin for error semantics for inexact knowledge invalidates axioms 4 and 5. We present a new semantics for modal logic which is shown to be complete for K45, without constraining the accessibility relation to be transitive or euclidean. The semantics corresponds to a system of modular knowledge, in which iterated modalities and simple modalities are not on a par. We show how the semantics helps to solve Williamson’s luminosity paradox, and argue that it corresponds to an integrated model of perceptual and introspective knowledge that is psychologically more plausible than the one defended by Williamson. We formulate a generalized version of the semantics, called token semantics, in which modalities are iteration-sensitive up to degree n and insensitive beyond n. The multi-agent version of the semantics yields a resource-sensitive logic with implications for the representation of common knowledge in situations of bounded rationality.


Inexact knowledge Epistemic logic Kripke semantics Token semantics Centered semantics Introspection Luminosity Vagueness Margin for error Common knowledge Bounded rationality 


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Département d’Etudes Cognitives, IHPSTEcole Normale SupérieureParisFrance
  2. 2.Département d’Etudes Cognitives, Institut Jean-Nicod, EHESS/ENS/CNRSEcole Normale SupérieureParisFrance

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