Modus tollens

Anglais

Modus tollens

n propositional logic, modus tollens[1][2][3][4] (or modus tollendo tollens and also denying the consequent)[5] (Latin for "the way that denies by denying")[6] is a valid argument form and a rule of inference. It is an application of the general truth that if a statement is true, then so is its contra-positive.

The first to explicitly describe the argument form modus tollens were the Stoics.[7]

The inference rule modus tollens validates the inference from P {\displaystyle P} P implies Q {\displaystyle Q} Q and the contradictory of Q {\displaystyle Q} Q to the contradictory of P {\displaystyle P} P.