modus ponens in full, modus ponendo ponens (Latin, ‘proposing method’), (1) the argument form ‘If A then B; A; therefore, B’, and arguments of this form (compare fallacy of affirming the consequent); (2) the rule of inference that permits one to infer the consequent of a conditional from that conditional and its antecedent. This is also known as the rule of /-elimination or rule of /- detachment. See also COUNTERFACTUALS , FOR- MAL FALLAC. G.F.S.