Modus Ponens and the Logic of Decision

Abstract

This article presents and discusses a prima facie counterexample to modus ponens. To appropriately theorize the case, I argue for conceptualizing the notions of logical consequence and logical commitment in “normative” terms, so that logical commitment does not attach to the premises of a spurious dominance argument—and, more generally, does not attach to unreasonable decision states, or to syntactically specified classes thereof. I also suggest that there is a logical motivation for the restriction to “well-formed” decision states that is characteristic of Savage-style logics of decision.