Abstract

Lee Archie argued that if any truth-values are consistently assigned to a natural language conditional, where modus ponens and modus tollens are valid argument forms, and affirming the consequent is invalid, this conditional will have the same truth-conditions as a material implication. This argument is simple and requires few and relatively uncontroversial assumptions. We show that it is possible to extend Archie’s argument to three- and five-valued logics and vindicate a slightly weaker conclusion, but one that is still important: Even if you do not believe in bivalence and the classical negation operator, you would still have good reasons to accept that natural language conditionals and the material implication share truth-conditions.