The book presents a thoroughly elaborated logical theory of generalized truth-values understood as subsets of some established set of truth values. After elucidating the importance of the very notion of a truth value in logic and philosophy, we examine some possible ways of generalizing this notion. The useful four-valued logic of first-degree entailment by Nuel Belnap and the notion of a bilattice constitute the basis for further generalizations. By doing so we elaborate the idea of a multilattice, and most notably, (...) a trilattice of truth values – a specific algebraic structure with information ordering and two distinct logical orderings, one for truth and another for falsity. Each logical order not only induces its own logical vocabulary, but determines also its own entailment relation. We consider both semantic and syntactic ways of formalizing these relations and construct various logical calculi. (shrink)

RESUMO O presente artigo apresenta uma semântica baseada nas atitudes cognitivas de aceitação e rejeição por uma sociedade de agentes para lógicas inspiradas no First Degree Entailment de Dunn e Belnap. Diferente das situações epistêmicas originalmente usadas em E, as atitudes cognitivas não coincidem com valores-de-verdade e parecem mais adequadas para as lógicas que pretendem considerar o conteúdo informacional de proposições “ditas verdadeiras” tanto quanto as proposições “ditas falsas” como determinantes da noção de validade das inferências. Após analisar algumas lógicas (...) associadas à semântica proposta, introduzimos a lógica E B cuja relação de consequência semântica subjacente - o B-entailment - é capaz de expressar diversos tipos de raciocínio em relação às atitudes cognitivas de aceitação e rejeição. Apresentamos também um cálculo de sequentes correto e completo para E B.ABSTRACT In the present work I introduce a semantics based on the cognitive attitudes of acceptation and rejection entertained by a given society of agents for logics inspired on Dunn and Belnap’s ‘First Degree Entailment’. Distinctly from the original epistemic situation of E, the cognitive attitudes do not coincide with truth-values and it seems more suitable for logics that intend to consider the informational content of propositions “said to be true” as well as propositions “said to be false” as determinants of the notion of logical validity. After analyzing some logics associated with the proposed semantics, we introduce the logic E B, whose underlying semantic entailment relation - the B-entailment - is able to express several kinds of reasoning towards the cognitive attitudes of acceptance and rejection. Acorrect and complete sequent calculus for E B is also presented. (shrink)

In this paper we present a solution of the axiomatization problem for the Fmla-Fmla versions of the Pietz and Rivieccio exactly true logic and the non-falsity logic dual to it. To prove the completeness of the corresponding binary consequence systems we introduce a specific proof-theoretic formalism, which allows us to deal simultaneously with two consequence relations within one logical system. These relations are hierarchically organized, so that one of them is treated as the basic for the resulting logic, and the (...) other is introduced as an extension of this basic relation. The proposed bi-consequences systems allow for a standard Henkin-style canonical model used in the completeness proof. The deductive equivalence of these bi-consequence systems to the corresponding binary consequence systems is proved. We also outline a family of the bi-consequence systems generated on the basis of the first-degree entailment logic up to the classic consequence. (shrink)