Found:

tautology

**SEMANTICS: **a sentence which is always true, not due to its word meanings but to its **logical form**. A tautology is
also called a logical truth or a
**necessary truth**. A sentence of
**propositional logic** is a tautology
when it is true for every possible assignment of
**truth value**s to the
**propositional letters** of that
sentence. The formula p v Neg p is a tautology of propositional logic. A sentence
of **predicate logic** is a tautology when
it is true for every possible denotation of the variables and individual and
predicate constants that it contains. The formula All(x) [ P(x) v Neg P(x) ] is a
tautology of predicate logic.

LIT. | Gamut, L.T.F. (1991) |