Possibility Frames and Forcing for Modal Logic

Fuente: arXiv
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Main Author: Holliday, Wesley H.
Format: Preprint
Published: 2025
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author Holliday, Wesley H.
author_facet Holliday, Wesley H.
contents This paper develops the model theory of normal modal logics based on partial "possibilities" instead of total "worlds," following Humberstone (1981) instead of Kripke (1963). Possibility semantics can be seen as extending to modal logic the semantics for classical logic used in weak forcing in set theory, or as semanticizing a negative translation of classical modal logic into intuitionistic modal logic. Thus, possibility frames are based on posets with accessibility relations, like intuitionistic modal frames, but with the constraint that the interpretation of every formula is a regular open set in the Alexandrov topology on the poset. The standard world frames for modal logic are the special case of possibility frames wherein the poset is discrete. We develop the beginnings of duality theory, definability/correspondence theory, and completeness theory for possibility frames.
format Preprint
id arxiv_https___arxiv_org_abs_2501_11768
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Possibility Frames and Forcing for Modal Logic
Holliday, Wesley H.
Logic
Logic in Computer Science
03B45, 03G05
This paper develops the model theory of normal modal logics based on partial "possibilities" instead of total "worlds," following Humberstone (1981) instead of Kripke (1963). Possibility semantics can be seen as extending to modal logic the semantics for classical logic used in weak forcing in set theory, or as semanticizing a negative translation of classical modal logic into intuitionistic modal logic. Thus, possibility frames are based on posets with accessibility relations, like intuitionistic modal frames, but with the constraint that the interpretation of every formula is a regular open set in the Alexandrov topology on the poset. The standard world frames for modal logic are the special case of possibility frames wherein the poset is discrete. We develop the beginnings of duality theory, definability/correspondence theory, and completeness theory for possibility frames.
title Possibility Frames and Forcing for Modal Logic
topic Logic
Logic in Computer Science
03B45, 03G05
url https://arxiv.org/abs/2501.11768