arXiv subjects

Abilio Rodrigues

Publications and source records attributed to Abilio Rodrigues.

7 recordsLinked to original sources

arXiv2026

Positive, Negative, and Reliable Information in a First-Order Logic of Evidence and Truth

In this paper we present the first-order logic QLETF+, a quantified version of the logic LETF+, introduced in Coniglio and Rodrigues (Studia Logica 112:561-606, 2024). QLETF+ exhibits several properties that are not always enjoyed by logics equipped with classicality operators. We show that it satisfies the replacement property and admits conjunctive, disjunctive, and prenex normal forms. Alongside extensions and anti-extensions, as in the previously studied first-order semantics for LETs, we make use here of what we call o-extensions: given an n-ary predicate symbol P, the o-extension of P is the set of n-tuples of individuals that satisfy the predicate oP. We prove the soundness and completeness of the deductive system of QLETF+ with respect to the six-valued first-order semantics.

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arXiv2024

On Universally Free First-Order Extensions of Belnap-Dunn's Four-Valued Logic and Nelson's Paraconsistent Logic N4

The aim of this paper is to introduce the logics FFDE and FN4, which are universally free versions of Belnap-Dunn's four-valued logic, also known as the logic of first-degree entailment (FDE), and Nelson's paraconsistent logic QN4 (N-). Both FDE and QN4 are suitable to be interpreted as information-based logics, that is, logics that are capable of representing the deductive behavior of possibly inconsistent and incomplete information in a database. Like QN4 and some non-free first-order extensions of FDE, FFDE and FN4 are endowed with Kripke-style variable domain semantics, which allows representing the dynamic aspect of information processing, that is, how a database receives new information over time, including information about new individuals. We argue, however, that FFDE and FN4 can better represent the development of inconsistent and incomplete information states (i.e., configurations of a database) over time than their non-free versions. First, because they allow for empty domains, which corresponds to the idea that a database may acknowledge no individual at all at an early stage of its development. Second, because they allow for empty names, which get interpreted as information about new individuals is inserted into the database. Also, both systems include an identity predicate that is interpreted along the same lines of the other logical operators, viz., in terms of independent positive and negative rules.

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arXiv2024

A defini\c{c}\~ao de verdade de Tarski

The aim of this text is to present, in a technically accessible way, Tarski's definition of truth, the indefinability theorem, and to discuss two aspects of Tarski's work on truth, namely, whether or not the definition captures the notion of truth as correspondence, and Kripke's objection to the hierarchy of languages.

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arXiv2024

Frege on the reference of sentences

The aim of this paper is to show that Frege's argument which concluded that the reference of a sentence is its truth-value, presented in 'On Sense and Reference' (1892), can be reconstructed taking into account the problems of the notion of conceptual content presented in the 'Begriffsschrift' (1879) and also other passages from a letter to Russell (1902) and the posthumous 'Logic in Mathematics' (1914). Once the `hybrid' notion of conceptual content was rejected as the semantic value of the expressions of the formal language designed to carry out the logicist project, there was no alternative between truth-values and thoughts. I claim that the reconstructed argument is perfectly sound and convincing.

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arXiv2024

Analytic proofs for logics of evidence and truth

This paper presents a sound, complete, and decidable analytic tableau system for the logic of evidence and truth \letf, introduced in Rodrigues, Bueno-Soler \& Carnielli (Synthese, DOI: 10.1007/s11229-020-02571-w, 2020). \letf\ is an extension of the logic of first-degree entailment (\fde), also known as Belnap-Dunn logic. \fde\ is a widely studied four-valued paraconsistent logic, with applications in computer science and in the algebra of processes. \letf\ extends \fde\ in a very natural way, by adding a classicality operator \cons, which recovers classical logic for propositions in its scope, and a non-classicality operator \incon, dual of \cons.

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arXiv2024

Normalization and cut-elimination theorems for some logics of evidence and truth

In this paper, we investigate proof-theoretic aspects of the logics of evidence and truth LETJ and LETF. These logics extend, respectively, Nelson's logic N and the logic of first-degree entailment FDE, also known as Belnap-Dunn four-valued logic, with a classicality operator that recovers classical logic for formulas in its scope. We will present natural deduction and sequent systems for LETJ and LETF, together with proofs of normalization and cut-elimination theorems, respectively. As a corollary, we obtain decidability for both logics.

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arXiv2023

On six-valued logics of evidence and truth expanding Belnap-Dunn four-valued logic

The main aim of this paper is to introduce the logics of evidence and truth LETK+ and LETF+ together with a sound, complete, and decidable six-valued deterministic semantics for them. These logics extend the logics LETK and LETF- with rules of propagation of classicality, which are inferences that express how the classicality operator o is transmitted from less complex to more complex sentences, and vice-versa. The six-valued semantics here proposed extends the 4 values of Belnap-Dunn logic with 2 more values that intend to represent (positive and negative) reliable information. A six-valued non-deterministic semantics for LETK is obtained by means of Nmatrices based on swap structures, and the six-valued semantics for LETK+ is then obtained by imposing restrictions on the semantics of LETK. These restrictions correspond exactly to the rules of propagation of classicality that extend LETK. The logic LETF+ is obtained as the implication-free fragment of LETK+. We also show that the 6 values of LETK+ and LETF+ define a lattice structure that extends the lattice L4 defined by the Belnap-Dunn four-valued logic with the 2 additional values mentioned above, intuitively interpreted as positive and negative reliable information. Finally, we also show that LETK+ is Blok-Pigozzi algebraizable and that its implication-free fragment LETF+ coincides with the degree-preserving logic of the involutive Stone algebras.

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