In logic, mous tollendo tollens (Latin for "the way that denies by denying") is the formal name for indirect proof or proof by contraposition (contrapositive inference), often abbreviated to MT or modus tollens. It can also be referred to as denying the consequent, and is a valid form of argument (unlike similarly-named but invalid arguments such as affirming the consequent or denying the antecedent). It is closely related to another valid form of argument, modus ponens or "affirming the antecedent".