Abstract

We approach the traditional problem of the relationship between opinion and truth, objects and appearances, from the standpoint and tools of logic of belief, combining an informal and technical approach. We describe and comment on some logics of individual concepts and modes of representation, and address the question of how to explain the possibility of a contradictory de re belief integrated with the corresponding non-contradictory de dicto belief. The QB logic is proposed, where the semantic problem is resolved (1) by extending the framework and model domain with the domain of appearances, with a special S-accessibility relation among worlds, and with non-rigid interpretation of appearance names, as well as (2) redefining the concept of satisfaction (and truth), including the satisfaction of identity statements, by relativizing satisfaction to the difference between things and appearances and to the S-accessibility of different epistemic alternatives. In doing so, all worlds are classical within themselves, while inconsistency and incompleteness in beliefs stem from different ways of connecting (merging and separating) worlds in determining the satisfaction of a formula.