The Unanticipated Examination in View of Kripke’s Semantics for Modal Logic

Abstract

Any attempt to characterize formally the set of sentences which a given person X knows to be true probably requires a certain amount of idealization. For the fact that he knows A to be true and knows B to be true can, one hopes, be determined by some kind of empirical investigation. If so, these facts are stubborn and irreducible, and X may know A but not B despite the fact that in some proposed formal system, A implies B. Still, it may be argued that X can be persuaded of B, given that he knows A, without informing him of any new contingent truths. For example, B may simply be a logical consequence of A, or it may follow, given certain other assumptions about knowledge which are held to be true of rational knowers.