In logic, specifically in deductive reasoning, an argument is valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. It is not required for a valid argument to … 展开

In logic, an argument is a set of related statements expressing the premises (which may consists of non-empirical evidence, empirical … 展开

Validity of deduction is not affected by the truth of the premise or the truth of the conclusion. The following deduction is perfectly valid: 展开

In truth-preserving validity, the interpretation under which all variables are assigned a truth value of 'true' produces a truth value of 'true'. 展开

A formula of a formal language is a valid formula if and only if it is true under every possible interpretation of the language. In propositional logic, they are tautologies. 展开

Model theory analyzes formulae with respect to particular classes of interpretation in suitable mathematical structures. On this reading, a formula is valid if all such interpretations make it true. An inference is valid if all interpretations that validate the … 展开

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