Definitions for modus tollens
This page provides all possible meanings and translations of the word modus tollens
A valid form of argument in which the consequent of a conditional proposition is denied, thus implying the denial of the antecedent. Modus tollens has this form:
Origin: From modus tollendo tollens, from modus and forms of tollo.
In propositional logic, modus tollens is a valid argument form and a rule of inference. The first to explicitly state the argument form modus tollens were the Stoics. The inference rule modus tollens, also known as the law of contrapositive, validates the inference from implies and the contradictory of, to the contradictory of . The modus tollens rule can be stated formally as: where stands for "P implies Q", stands for "it is not the case that Q". Then, whenever "" and "" each appear by themselves as a line of a proof, "" can validly be placed on a subsequent line. The history of the inference rule modus tollens goes back to antiquity. Modus tollens is closely related to modus ponens. There are two similar, but invalid, argument forms known as affirming the consequent and denying the antecedent.
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"modus tollens." Definitions.net. STANDS4 LLC, 2014. Web. 8 Mar. 2014. <http://www.definitions.net/definition/modus tollens>.