A Note on Flagg and Friedman's Epistemic and Intuitionistic Formal Systems

Abstract

We report our findings on the properties of Flagg and Friedman's translation from Epistemic into Intuitionistic logic, which was proposed as the basis of a comprehensive proof method for the faithfulness of the Goodel translation. We focus on the propositional case and raise the issue of the admissibility of the translated necessitation rule. Then, we contribute to Flagg and Friedman's program by giving an explicit proof of the soundness of their translation.