Valuation semantics for first-order logics of evidence and truth (and some related logics)

Abstract

This paper introduces the logic $QLE{T}_F$, a quantified extension of the logic of evidence and truth $LE{T}_F$, together with a corresponding sound and complete first-order non-deterministic valuation semantics. $LE{T}_F$ is a paraconsistent and paracomplete sentential logic that extends the logic of first-degree entailment ($FDE$) with a classicality operator $\circ$ and a non-classicality operator $\bullet$, dual to each other: while $\circ A$ entails that $A$ behaves classically, $\bullet A$ follows from $A$'s violating some classically valid inferences. The semantics of $QLE{T}_F$ combines structures that interpret negated predicates in terms of anti-extensions with first-order non-deterministic valuations, and completeness is obtained through a generalization of Henkin's method. By providing sound and complete semantics for first-order extensions of $FDE$, $K3$, and $LP$, we show how these tools, which we call here the method of ``anti-extensions + valuations'', can be naturally applied to a number of non-classical logics.