• Media type: E-Article
  • Title: Derivation rules as anti-axioms in modal logic
  • Contributor: Venema, Yde
  • imprint: Cambridge University Press (CUP), 1993
  • Published in: Journal of Symbolic Logic
  • Language: English
  • DOI: 10.2307/2275109
  • ISSN: 0022-4812; 1943-5886
  • Origination:
  • Footnote:
  • Description: <jats:title>Abstract</jats:title><jats:p>We discuss a ‘negative’ way of defining frame classes in (multi)modal logic, and address the question of whether these classes can be axiomatized by<jats:italic>derivation rules</jats:italic>, the ‘non-ξ rules’, styled after Gabbay's Irreflexivity Rule. The main result of this paper is a metatheorem on completeness, of the following kind: If<jats:italic>⋀</jats:italic>is a derivation system having a set of axioms that are special Sahlqvist formulas and<jats:italic>⋀</jats:italic><jats:sup>+</jats:sup>is the extension of<jats:italic>⋀</jats:italic>with a set of non-ξ rules, then<jats:italic>⋀</jats:italic><jats:sup>+</jats:sup>is strongly sound and complete with respect to the class of frames determined by the axioms and the rules.</jats:p>