Logical law

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in mathematical logic

A logical formula that becomes a true proposition under any interpretation of the variables for propositions and predicates that occur in it. Such formulas are called generally valid, universally valid or tautologies. For example, the tautology $A\lor\neg A$ expresses the law of the excluded middle.



[a1] A. Grzegorczyk, "An outline of mathematical logic" , Reidel (1974)
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Logical law. Encyclopedia of Mathematics. URL:
This article was adapted from an original article by V.E. Plisko (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article