| A number of related fully quantified epistemic-doxastic logics are developed from a study of various epistemic principles. These logics countence constructions such as "Everyone knows that ...", hence are more expressive then Hintikka's epistemic-doxastic logic. A two sorted presupposition-free base logic is employed to distinguish those things capable of knowledge and belief from those which are not, and to distinguish denoting from non-denoting terms. Logics for both concurrent and virtual senses of "Knowledge" and "belief" are developed, both axiomatically and semantically. The logic of occurrent knowledge and belief requires only that knowledge entail both truth and belief. Inconsistent belief sets are permitted. The logics for virtual knowledge and belief require in addition logical omniscience, and optionally the KK-thesis. Three sorts of epistemic contexts are considered, transparent, opaque in the sense of Hintikka, and fully opaque contexts. At various points, both frame-theoretic and truth-value semantic accounts are employed. Soundness and completeness theorems are provided for representative logics, the latter being of the Henkin sort. |
