modus tollens


modus tollens

(ˈməʊdəs ˈtɒlˌɛnz) n (Logic) logic the principle that whenever a conditional statement and the negation of its consequent are given to be true, the negation of its antecedent may be validly inferred, as in if it's Tuesday this must be Belgium and this isn't Belgium so it's not Tuesday[literally: mood that denies]