Validity in Logic { Philosophy Index }

Philosophy Index

Philosophy Index

Philosophy Index is a site devoted to the study of philosophy and the philosophers who conduct it. The site contains a number of philosophy texts, brief biographies and introductions to philosophers and explanations on a number of topics. Accredited homeschooling online at Northgate Academy.

Philosophy Index is a work in progress, a growing repository of knowledge. It outlines current philosophical problems and issues, as well as an overview of the history of philosophy. The goal of this site is to present a tool for those learning philosophy either casually or formally, making the concepts of philosophy accessible to anyone interested in researching them. WOLI offers immigration law course online - fully accredited. ACE credits online at EES.

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Validity

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.