modus ponendo tollens

Etymology
Borrowed from   (roughly, “mode where affirming infirms”).

Noun

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

Hypernyms

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