In
and the rule
Every regular modal logic is classical, and every
References
Chellas, Brian. "Modal Logic: An Introduction". Cambridge University Press, 1980.
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Modal logic — is a type of formal logic that extends classical propositional and predicate logic to include operators expressing modality. Modals words that express modalities qualify a statement. For example, the statement John is happy might be qualified by… … Wikipedia
Classical modal logic — In modal logic, a classical modal logic L is any modal logic containing (as axiom or theorem) the duality of the modal operators which is also closed under the rule Alternatively one can give a dual definition of L by which L is classical iff it… … Wikipedia
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Modal verb — A modal verb (also modal, modal auxiliary verb, modal auxiliary) is a type of auxiliary verb that is used to indicate modality that is, likelihood, ability, permission, and obligation.[1]:p.33 The use of auxiliary verbs to express modality is… … Wikipedia
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Interior algebra — In abstract algebra, an interior algebra is a certain type of algebraic structure that encodes the idea of the topological interior of a set. Interior algebras are to topology and the modal logic S4 what Boolean algebras are to set theory and… … Wikipedia
Method of analytic tableaux — A graphical representation of a partially built propositional tableau In proof theory, the semantic tableau (or truth tree) is a decision procedure for sentential and related logics, and a proof procedure for formulas of first order logic. The… … Wikipedia
Admissible rule — In logic, a rule of inference is admissible in a formal system if the set of theorems of the system is closed under the rule. The concept of an admissible rule was introduced by Paul Lorenzen (1955).DefinitionsThe concept of admissibility, as… … Wikipedia
