Informational dynamics of epistemic possibility modals
We investigate, in a logical setting, the expressivist proposal that assertion primarily functions to express and coordinate doxastic states and that ‘might’ fundamentally expresses lack of belief. We provide a formal model of an agent’s doxastic state and novel assertability conditions for an associated formal language. We thereby prove that an arbitrary assertion (including a complex of ‘might’ and ‘factual’ claims) always succeeds in expressing a well-defined (partial) doxastic state, and propose a fully general and intuitive update operation as a model of an agent coming to accept an arbitrary assertion. Leaving a comprehensive philosophical and linguistic defense for elsewhere, we explore technical aspects of our framework, providing, for instance, a complete logic of assertability and reduction axioms for the novel update operations related to our proposal. Finally, we contrast our work with related proposals in the logic literature.
KeywordsEpistemic modality Information dynamics Epistemic possibility Assertion Assertability logic Doxastic update
The authors wish to thank the following people for providing comments that helped in the development of this paper (of course, any remaining errors or other infelicities in the paper remain the authors’ sole responsibility): the audience at LORI-V, Rob Bassett, Johan van Benthem, Michael Cohen, Cleo Condoravdi, Sophie Dandelet, Tom Donaldson, Melissa Fusco, Lelia Glass, Dave Gottlieb, Thomas icard, David Israel, Lauri Kartunnen, Dan Lassiter, Meica Magnani, Katy Meadows, Prerna Nadathur and Seth Yalcin. Special thanks to our anonymous referees and Alex Kocurek for very detailed comments. Thanks to the organizers of LORI-V and especially to Wen-fang Wang. This paper was developed at the Logical Dynamics Lab at CSLi, Stanford University.
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