Lógica e Direito : elementos para uma reconstrução formal do raciocínio jurídico

Abstract

Resumo: A tese analisa diversos aspectos do raciocinio juridico de um ponto de vista logico-formal. Paradoxos semanticos, como o paradoxo do mentiroso, e a auto-referencia na linguagem juridica, como a possilibidade de reforma das regras que preveem a reforma de uma Constituicao, segundo o proprio procedimento de reforma constitucional, sao examinados atraves das categorias de linguagem objeto e metalinguagem de A. TARSKI. Utilizando a distincao entre intensao e extensao, os termos modais, referentes as nocoes de necessidade e possibilidade, e os termos deonticos, referentes as nocoes de obrigacao, permissao e proibicao, sao definidos como termos intensionais. Um exemplo simples de semantica intensional e apresentado, alem das similaridades entre as nocoes deonticas e modais. A tese de que ha uma distincao de natureza logica entre regras e principios juridicos, defendida por R. DWORKIN, e examinada atraves de um sistema de Logica baseada em Razoes, formulado por B. VERHEIJ, J.C. HAGE e H.J. VAN DEN HERIK, o qual contradiz esta tese e fornece uma visao integrada entre regras e principios. O carater falivel ou derrotavel dos principios juridicos e do raciocinio juridico, bem como o conflito de normas juridicas sao examinados atraves de varios sistemas logicos. Uma primeira limitacao da logica classica e sua caracteristica monotonica: a adicao de novas informacoes a um conjunto finito de premissas nao altera as conclusoes deduzidas do conjunto inicial, ao contrario do raciocinio juridico, no qual a conclusao muda a cada nova informacao ou premissa. Uma segunda limitacao da logica classica refere-se a impossibilidade de representacao de enunciados contraditorios, ao contrario do raciocinio juridico, o qual considera a possibilidade de normas, informacoes ou premissas contraditorias. Como alternativa a primeira limitacao sao formuladas as logicas nao monotonicas; a segunda limitacao, as logicas paraconsistentes. Sao expostas as propriedades formais que uma relacao de consequencia nao monotonica deve obedecer. As Razoes prima facie de C.E. ALCHOURRON, a extracao e derrogacao de ALCHOURRON e D. MAKINSON, a teoria AGM, uma logica deontica paraconsistente de N.C.A. DA COSTA e W. CARNIELLI, a abordagem paraconsistente da teoria AGM de DA COSTA e BUENO, e a logica paraconsistente anotada sao objeto de discussao e analise sobre as possibilidades e vantagens comparativas de cada um destes sistemas em reconstruir formalmente o raciocinio juridico, de forma que a naomonotonicidade e os conflitos normativos possam ser adequadamente representados. Palavras-chave: raciocinio juridico; paradoxos; principios juridicos; intensionalidade; logica deontica; logica nao-monotonica; logica paraconsistente.

Abstract: The thesis analyzes several aspects of juridical reasoning from a logical-formal point of view. Semantic paradoxes, as the liar's paradox, and the self-reference in juridical language, as the possilibility of reform of the rules that govern the reform of a Constitution, according to the own procedure of constitutional reform, are examined through the categories of language object and meta-language from A. TARSKI. Using the distinction between intension and extension, the modal terms, regarding the necessity and possibility notions, and deontic terms, like the obligation, permission and forbidden notions, are defined as intensional terms. A simple example of intensional semantics and the similarities between deontic and modal notions are presented. The theory that claims that there is a distinction of logical nature between rules and juridical principles, defended by R. DWORKIN, is examined through a system of Logic Based in Reasons, formulated by B. VERHEIJ, J.C. HAGE and H.J. VAN DEN HERIK, which contradicts this theory and supplies a conception in which rules and principles are integrated. The fallible or defeasible character of juridical principles and juridical reasoning, as well as the conflict between juridical norms are examined through several logical systems. A first limitation of classical logic is its monotonic character: the addition of a new information to a finite set of premises does not change the conclusions that can be deduced from the initial set, unlike the juridical reasoning, in which the conclusion changes to each new information or premise added. A second limitation of classical logic refers to the impossibility of representation of contradictory statements, unlike the juridical reasoning, which considers the possibility of contradictory norms, information or premises. As an alternative to the first limitation, the non monotonic logics are formulated; to the second limitation, the paraconsistent logics. The formal properties that a non monotonic consequence relation should obey are exposed. The prima facie Reasons of C.E. ALCHOURRON, the delivery and derogation of ALCHOURRON and D. MAKINSON, the AGM theory, a paraconsistent deontic logic of N.C.A. DA COSTA and W. CARNIELLI, the paraconsistent approach of AGM theory of DA COSTA and BUENO, and the annotated paraconsistent logic are object of discussion and analysis about the possibilities and comparative advantages of each one of these systems in formally reconstructing the juridical reasoning, so that the non-monotony and the normative conflicts can be appropriately represented. Key-words: juridical reasoning; paradoxes; principles ; intensionality; deontic monotonie logic; paraconsistent logic.