Modus tollens

Modus tollendo tollens (Latin: the way that denies by denying) is a valid, simple argument form in classical logic. It is referred to as denying the consequent. It is closely related to another valid form of argument, modus ponens or affirming the antecedent. Modus tollens is a very common rule of inference, and takes this form:
If P, then Q.
Not Q.
Therefore, not P.University of North Carolina, Philosophy Department, Logic Glossary .

References

Category:Rules of inference