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.
|[a1]||A. Grzegorczyk, "An outline of mathematical logic" , Reidel (1974)|
Logical law. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Logical_law&oldid=18440