Le fantôme de la modalité
We introduce various kinds of fixed-point properties for modal logics, and we classify the most prominent systems according to these. Our goal is to do a first step towards a complete characterization of provability logics of (possibly non standard) derivability predicates for Peano Arithmetic.
In this paper we present logics about stable and unstable versions of several well-known relations from mereology: part-of, overlap and underlap. An intuitive semantics is given for the stable and unstable relations, describing them as dynamic counterparts of the base mereological relations. Stable relations are described as ones that always hold, while unstable relations hold sometimes. A set of first-order sentences is provided to serve as axioms for the stable and unstable relations, and representation...