LIRa session: Peter Hawke

Speaker: Peter Hawke (ILLC, Amsterdam)

Date and Time: Thursday, November 23rd 2017, 16:00-17:30

Venue: KdVI Seminar Room F3.20, Science Park 107.

Title: Epistemic Logic as Knowability Relative to Information.

Abstract. We present a formal semantics for epistemic logic, aimed at capturing the notion of knowability relative to information (KRI). We move from Dretske’s account of the nature of information, along with his insight that what an agent can know depends on her (empirical) information. We treat operators of the form KAB (‘B is knowable on the basis of information A’) as variably strict quantifiers over worlds with a topic- or aboutness- preservation constraint. Thus, we develop epistemic logic as a conditional logic. Variable strictness models the non-monotonicity of knowledge acquisition while ensuring a more basic sense in which knowledge is stable. Aboutness-preservation models the topic-sensitivity of information, allowing us to invalidate controversial forms of epistemic closure while validating less controversial ones. Thus, unlike the standard modal framework for epistemic logic (i.e. in the style of Hintikka), KRI accommodates various plausible approaches to the Kripke-Harman dogmatism paradox. KRI also strikes a better balance between agent idealization and a non-trivial logic of knowledge ascriptions. In this talk, we focus on foundational motivations, leaving meta-logical results for elsewhere.