# Logical law

From Encyclopedia of Mathematics

*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 expresses the law of the excluded middle.

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#### References

[a1] | A. Grzegorczyk, "An outline of mathematical logic" , Reidel (1974) |

**How to Cite This Entry:**

Logical law.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Logical_law&oldid=18440

This article was adapted from an original article by V.E. Plisko (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article