The Real truth

TL;DR

This paper introduces R-valued logic, an extension of continuous propositional logic with unbounded truth values, establishing its semantics, deduction rules, and completeness properties, and relating it to Lukasiewicz logic.

Contribution

It develops the formal framework of R-valued logic, including semantics, deduction, and completeness, and connects it to existing many-valued logics.

Findings

Proves completeness for finite theories in R-valued logic.

Characterizes unital and Archimedean theories within R-valued logic.

Provides alternative calculi for Lukasiewicz and continuous propositional logic.

Abstract

We study a real valued propositional logic with unbounded positive and negative truth values that we call R-valued logic. Such logic slightly extends continuous propositional logic which, in turn, builds on Lukasiewicz many-valued logic. After presenting the deduction machinery and the semantics of R-valued logic, we prove a completeness theorem for finite theories. Then we define unital and Archimedean theories, in accordance with the theory of Riesz spaces. In the unital setting, we prove the equivalence of consistency and satisfiability and an approximated completeness theorem similar to the one that holds for continuous propositional logic. Eventually, among unital theories, we characterize Archimedean theories as those for which strong completeness holds. We also point out that R-valued logic provides alternative calculi for Lukasiewicz and for propositional continuous logic.