modal tautology

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• Entailment — For other uses, see Entail (disambiguation). In logic, entailment is a relation between a set of sentences (e.g.,[1] meaningfully declarative sentences or truthbearers) and a sentence. Let Γ be a set of one or more sentences; let S1 be the… …   Wikipedia

• Propositional calculus — In mathematical logic, a propositional calculus or logic (also called sentential calculus or sentential logic) is a formal system in which formulas of a formal language may be interpreted as representing propositions. A system of inference rules… …   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

• Outline of logic — The following outline is provided as an overview of and topical guide to logic: Logic – formal science of using reason, considered a branch of both philosophy and mathematics. Logic investigates and classifies the structure of statements and… …   Wikipedia

• Ontological argument — The ontological argument for the existence of God (or simply ontological argument) is an a priori proof for the existence of God. The ontological argument was first proposed by the eleventh century monk Anselm of Canterbury, who defined God as… …   Wikipedia

• Kripke semantics — (also known as relational semantics or frame semantics, and often confused with possible world semantics) is a formal semantics for non classical logic systems created in the late 1950s and early 1960s by Saul Kripke. It was first made for modal… …   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

• Logical truth — is one of the most fundamental concepts in logic, and there are different theories on its nature. A logical truth is a statement which is true and remains true under all reinterpretations of its components other than its logical constants. It is… …   Wikipedia

• Doxastic logic — is a modal logic concerned with reasoning about beliefs. The term doxastic derives from the ancient Greek δόξα, doxa, which means belief. Typically, a doxastic logic uses Bx to mean It is believed that x is the case, and the set denotes a set of… …   Wikipedia

• Logical consequence — Therefore redirects here. For the symbol, see therefore sign. Logical consequence is a fundamental concept in logic. It is the relation that holds between a set of sentences (or propositions) and a sentence (proposition) when the former entails… …   Wikipedia

• Deontic logic — is the field of logic that is concerned with obligation, permission, and related concepts. Alternatively, a deontic logic is a formal system that attempts to capture the essential logical features of these concepts. Typically, a deontic logic… …   Wikipedia