Publication details

EF4, EF4-M and EF4-Ł: A companion to BN4 and two modal four-valued systems without strong Łukasiewicz-type modal paradoxes



Year of publication 2021
Type Article in Periodical
Magazine / Source Logic and logical philosophy
Keywords relevant logics, modal logics, many-valued logics, Belnap-Dunn semantics, modal paradoxes, 4-valued modal logics
Description The logic BN4 was defined by RT Brady as a four-valued extension of Routley and Meyer’s basic logic B. The system EF4 is defined as a companion to BN4 to represent the four-valued system of (relevant) implication. The system Ł was defined by J. Łukasiewicz and it is a four-valued modal logic that validates what is known as strong Łukasiewicz-type modal paradoxes. The systems EF4-M and EF4-Ł are defined as alternatives to Ł without modal paradoxes. This paper aims to define a Belnap-Dunn semantics for EF4, EF4-M and EF4-Ł. It is shown that EF4, EF4-M and EF4-Ł are strongly sound and complete wrt their respective semantics and that EF4-M and EF4-Ł are free from strong Łukasiewicz-type modal paradoxes.

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