On Łukasiewicz's Four-Valued Modal Logic

摘要

Łukasiewicz's four-valued modal logic is surveyed and analyzed, together with Łukasiewicz's motivations to develop it. A faithful interpretation of it in classical (non-modal) two-valued logic is presented, and some consequences are drawn concerning its classification and its algebraic behaviour. Some counter-intuitive aspects of this logic are discussed in the light of the presented results, Łukasiewicz's own texts, and related literature.