The fundamental problem of logical omniscience

Peter Hawke, Aybüke Özgün, Franz Berto

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1 Citation (Scopus)


We propose a solution to the problem of logical omniscience in what we take to be its fundamental version: as concerning arbitrary agents and the knowledge attitude per se. Our logic of knowledge is a spin-off from a general theory of thick content, whereby the content of a sentence has two components: (i) an intension, taking care of truth conditions; and (ii) a topic, taking care of subject matter. We present a list of plausible logical validities and invalidities for the logic of knowledge per se for arbitrary agents, and isolate three explanatory factors for them: (1) the topic-sensitivity of content; (2) the fragmentation of knowledge states; (3) the defeasibility of knowledge acquisition. We then present a novel dynamic epistemic logic that yields precisely the desired validities and invalidities, for which we provide expressivity and completeness results. We contrast this with related systems and address possible objections.
Original languageEnglish
Number of pages40
JournalJournal of Philosophical Logic
VolumeOnline First
Early online date20 Dec 2019
Publication statusE-pub ahead of print - 20 Dec 2019


  • Aboutness
  • Subject matter
  • Logical omniscience
  • Dynamic epistemic logic
  • Thick content


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