# Talk: Johannes Stern (Bristol/MCMP)

Location: Ludwigstr. 31, ground floor, Room 021.

13.02.2020 16:00 – 18:00

## Title:

The Modal Logic of Kripkean Truth (joint work with Carlo Nicolai)

## Abstract:

We determine the modal logic of fixed-point models of truth and their axiomatizations by Solomon Feferman via Solovay-style completeness results. Given a fixed-point model **M**, or an axiomatization S thereof, we find a modal logic M such that a modal sentence A is a theorem of M if and only if the sentence A* obtained by translating the modal operator with the truth predicate is true in **M** or a theorem of S under all such translations. To this end, we introduce a novel possible world semantics featuring both classical and subclassical worlds and establish the completeness of a familiy of non-classical modal logics (in the sense of Segerberg) modal logics, whose internal logic is subclassical, with respect to this semantics. In a second step we show how to emulate the models of the modal logic within the lattice of Kripkean fixed-point models.