A Hilbert Calculus for Logic of Truth-Functional Contingency

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Studies in Logic, Vol. 14, No. 3 (2021): 24–36   PII: 1674-3202(2021)-03-0024-13

Fei Liang   Zhongxu Tian   Xinyu Yang

Abstract.

A statement is truth-functionally contingent, if it is neither a tautology nor a contradiction in classical propositional logic. The logic of truth-functional contingency, is to capture all these contingent statements. In this paper, we introduce a sound and complete Hilbert calculus for the logic of truth-functional contingency, where every formula introduced in a deduction is a contingent formula, and it is introduced only if it is a contingent axiom, or it follows by one of the contingent rules of inference from contingent formulas introduced earlier in the deduction.