modus tollendo ponens

Etymology
Borrowed from   (roughly, “mode where negating confirms”).

Noun

 * 1)  A valid form of argument in which the antecedent of a conditional proposition is negated, thereby entailing the affirmation of the consequent. Modus ponendo tollens has the form:
 * 1. Either P or Q.
 * 2. non-P.
 * 3. Therefore, Q.

Hypernyms

 * See also Thesaurus:argument form
 * See also Thesaurus:argument form