Abstract

This article examines some philosophical questions about knowledge of modality, including how we determine whether a proposition is necessary or contingent and what procedures to use for recognizing possibility. It maintains that virtually anything is conceivable, and that conceivability is therefore incapable of providing a reliable test for possibility. Whether a conceivable state of affairs is genuinely possible depends on whether it is compatible with the class of necessary truths. But this means that we must have some independent way of recognizing necessity. The article explains that independent access to necessity in terms of the hypothesis that various modal truths constitute an implicit definition of necessity. To a large extent, our knowledge of necessity derives from our grasp of this definition. The article also criticizes Cartesian modal arguments for dualism, and raises an objection to the view that metaphysical necessity can be reductively explained in terms of subjunctive conditionals.