Knowability as De Re Modality: A Certain Solution to Fitch Paradox

Tomasz Jarmużek; Krzysztof Krawczyk; Rafał Palczewski

doi:10.18290/rf20684-14

Tomasz Jarmużek Nicolaus Copernicus University in Toruń, Faculty of Philosophy and Social Sciences, Poland https://orcid.org/0000-0003-3456-3859
Krzysztof Krawczyk Nicolaus Copernicus University in Toruń, Faculty of Philosophy and Social Sciences, Poland https://orcid.org/0000-0003-4367-4796
Rafał Palczewski Nicolaus Copernicus University in Toruń, Faculty of Philosophy and Social Sciences, Poland

DOI: https://doi.org/10.18290/rf20684-14

Keywords: anti-realism, de dicto modality, de re modality, epistemic logic, Fitch Paradox, knowability logic, knowability principle, modal logic, tableaux methods

Abstract

In the paper, we try to find a new, intuitive solution to the Fitch paradox. We claim that traditional expression of Knowability Principle (p → ◊Kp) is based on erroneous understanding of knowability as de dicto modality. Instead, we propose to understand knowability as de re modality. In the paper we present the minimal logic of knowability in which Knowability Principle is valid, but Fitch Paradox does not hold anymore. We characterize the logic semantically as well as by an axiomatic and tableaux procedure approach.

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