Core Concepts
The paper deals with the problem of axiomatizing the transitive logic of false belief, which was previously thought to be difficult. It proposes an "almost definability" schema that guides the discovery of core axioms for the transitive and Euclidean logics of false belief. It also introduces a suitable canonical relation that enables uniform completeness proofs for various logics of false belief, including the transitive logic. Furthermore, the paper extends the results to the logic of radical ignorance, showing that the operators of false belief and radical ignorance are interdefinable.
Abstract
The paper focuses on the logical study of false belief and radical ignorance. It starts by introducing the language and semantics of the logic of false belief, and proposes an "almost definability" schema that relates the standard doxastic operator and the false belief operator.
The paper then investigates the expressive power and frame definability of the logic of false belief, showing that it is less expressive than standard doxastic logic on various classes of models. It also identifies a class of narcissistic frames where the two logics are equally expressive.
The main contribution of the paper is the axiomatization of various logics of false belief, including the minimal logic, the serial logic, the transitive logic, and the Euclidean logic. The axiomatization of the transitive logic solves an open problem raised in previous work. The key ideas are: (1) the "almost definability" schema guides the discovery of the core axioms, and (2) a suitable canonical relation is introduced to enable uniform completeness proofs.
Finally, the paper extends the results to the logic of radical ignorance, showing that the operators of false belief and radical ignorance are interdefinable. It axiomatizes the minimal logic and the serial/transitive logic of radical ignorance.