http://dx.doi.org/10.5007/1808-1711.2009v13n3p357 Neste trabalho concorda-se com a tese de I. Hacking segundo a qual o significado das constantes lógicas é dado pelas Regras de Introdução e Eliminação do cálculo de sequentes de Gentzen que caracterizam a concepção da noção de consequência lógica abstrata. Perguntamos quais são as regras mínimas que um conectivo deve satisfazer para que seja considerado uma negação genuína. Tomaremos como referência para tratar dessa questão os C-sistemas de Newton da Costa e o sistema LP de Graham Priest. Finalmente, (...) analisaremos esses sistemas na lógica de sequentes a fim de mostrar que a negação paraconsistente ou bem carece das regras puras de eliminação e negação da negação ou ela envolve outros conectivos, o que torna difícil atribuir um significado unívoco à negação paraconsistente. (shrink)

In this paper we present a new hierarchy of analytical tableaux systems TNDC n, 1≤n (...) and also prove that these systems are logically equivalent to the corresponding systems Cn, 1≤nshrink)

In this paper we present a new hierarchy of analytical tableaux systems TNDC n, 1≤n<ω, for da Costa's hierarchy of propositional paraconsistent logics Cn, 1≤n<ω. In our tableaux formulation, we introduce da Costa's “ball” operator “o”, the generalized operators “k” and “(k)”, for 1≤k, and the negations “~k”, for k≥1, as primitive operators, differently to what has been done in the literature, where these operators are usually defined operators. We prove a version of Cut Rule for the TNDC n, 1≤n<ω, (...) and also prove that these systems are logically equivalent to the corresponding systems Cn, 1≤n<ω. The systems TNDC n constitute completely automated theorem proving systems for the systems of da Costa's hierarchy Cn, 1≤n<ω. (shrink)

A conjectural inference is proposed, aimed at producing conjectural theorems from formal conjectures assumed as axioms, as well as admitting contradictory statements as conjectural theorems. To this end, we employ Paraconsistent Informational Logic, which provides a formal setting where the notion of conjecture formulated by an epistemic agent can be defined. The paraconsistent systems on which conjectural deduction is based are sequent formulations of the C-systems presented in Carnielli-Marcos [CAR 02b]. Thus, conjectural deduction may also be considered to be a (...) tool for investigating the properties of paraconsistency in general. (shrink)