Clearly, the logic mbC is the minimal extension of CPL + having a consistency operator • and a paraconsistent negation ¬, and such that it is an LFI. In this chapter, several extensions of mbC will be proposed, taking into account different features of mbC that can be strengthened or expanded.
A Wider Form of Truth-Functionality for ConsistencyBy observing the quasi-matrices presented in Sect. 2.3 of Chap. 2, it becomes clear that not every connective of mbC is truth-functional (w.r.t. valuations): the tables for ¬ and • show that non-determinism exists, to a certain extent, in the evaluation process. This aspect is not a defect of the valuations for mbC: it can be proven that mbC (and several extensions of it) are not characterizable by finite matrices, adapting J. Dugundji's argument for modal logics. This topic will be briefly analyzed in Sect. 4.2 of Chap. 4.Returning to the valuation semantics for mbC, it is clear that the truth-value of a formula α partially determines the truth-value of ¬α: if α is false then ¬α must be true, but when α is true the truth-value of ¬α cannot be determined: it can be either true or false. Similarly, the truth-values of α and ¬α partially determine the truthvalue of •α in mbC: if they are both true then •α must be false, but if one of {α, ¬α} is false and the other is true (that is, if the truth-values of α and ¬α are different), the truth-value of •α is undetermined: it can be either true or false. In [1] an extension of mbC called mCi was researched, which guarantees that the truth-values of α and ¬α are sufficient to determine the truth-value of •α. However, this extension also 1 In general, names of logic systems are acronyms for the names of the axioms involved.