Philosophy Index


The term validity is most frequently used to describe whether or not an argument appropriately uses reason to determine its conclusion, though it may also refer to the truth-value or a proposition.

Validity of Arguments

An argument form is considered to be valid when no valuation of its terms makes all of its premises true and all of its conclusions false. More genearlly, a valid argument is one which, if all of its premises are true, always produces a true conclusion.

Several valid argument forms are known, and are used by logicians and philosophers to evaluate arguments.

Arguments that produce false conclusions despite the truth of their conclusions are called invalid. The use of an invalid argument form may lead to a logical fallacy.

Semantic Validity of Formulas

Semantic validity with respect to an individual formula, such as β or ((A ∨ B) → C), refers to whether or not a formula is true on every valuation of its terms. A semantically valid formula is therefore a tautology.