Clement Lion

“Logic and Agon” is the text of a lecture given in Rome in 1958 by the German philosopher and mathematician Paul Lorenzen. In this inaugural text are laid the foundations of the dialogic logic, which represents an alternative approach to the question of meaning and logical truth, based on a dynamic formalism. Through the enrichment of the standard approach to logic with original tools, it allows a philosophical explanation of the foundations of the concept of formal validity. Clément Lion proposes an unpublished French translation of this text as well as a presentation, in which he tries to show that the initial ambition of Paul Lorenzen was not so much to propose a new logical formalism as to question in principle any enterprise based on the use of such a formalism.

“Logic and Agon” is the text of a lecture given in Rome in 1958 by the German philosopher and mathematician Paul Lorenzen. In this inaugural text are laid the foundations of the dialogic logic, which represents an alternative approach to the question of meaning and logical truth, based on a dynamic formalism. Through the enrichment of the standard approach to logic with original tools, it allows a philosophical explanation of the foundations of the concept of formal validity. Clément Lion proposes an unpublished French translation of this text as well as a presentation, in which he tries to show that the initial ambition of Paul Lorenzen was not so much to propose a new logical formalism as to question in principle any enterprise based on the use of such a formalism.

Avec l’article « Aristotle’s natural deduction system », publié en 1974, J. Corcoran a contribué à diffuser une nouvelle perspective sur les écrits logiques d’Aristote et sur la théorie du syllogisme en particulier. Dans cet article, Corcoran affirme que, dans les premiers chapitres des Premiers Analytiques, Aristote ne propose pas un système axiomatique, qui supposerait une logique sous-jacente, ainsi que le pensait Łukasiewicz, mais plutôt un système de déduction naturelle, avec des dimensions métalogiques. Notre propos est ici basé sur une courte monographie de Kurt Ebbinghaus, intitulée Ein formales Model der Syllogistik des Aristoteles (1964), où est fixé le canon de cette nouvelle perspective mentionnée plus haut et qui a été développé dans le cadre conceptuel de la « logique opérative » de Paul Lorenzen. Ebbinghaus développe une reconstruction formelle montrant que l’approche d’Aristote relève de la « théorie de la preuve », non seulement pour ce qui concerne le système d’inférence sous-jacent, mais aussi pour ce qui concerne les éléments métalogiques. C’est notamment à travers ce dernier aspect que se manifeste une différence majeure par rapport à la reconstruction de Corcoran. Alors que celui-ci pose que le système d’inférence d’Aristote est enraciné dans une sémantique de théorie des modèles (élaborée par Corcoran lui-même), Ebbinghaus comprend que la théorie du syllogisme a été développée à partir d’une approche de la signification par des règles (« rule based »), semblables aux règles d’un jeu. En fait, la reconstruction d’Ebbinghaus offre une lecture pragmatiste de la syllogistique d’Aristote, qui, tel est notre propos, paraît non seulement beaucoup plus proche du point de vue d’Aristote que ne l’est la sémantique de théorie des modèles proposée par Corcoran, mais qui, de plus, permet de saisir l’unité systématique de la théorie du syllogisme.

We argue that the recent developments of the dialogical framework towards the incorporation of materiality within dialogues certainly enables one to extend its possible applications beyond the domain of logic. We ask the question of linking Bakhtin’s criticism of literary formalism, based on advocating dialogical features within novels, and the dialogical sight on formalism, in order to assess the program of constituting a dynamical formalism as a means towards literary analysis, enabling to speak of subjectivity without falling into psychologism. By the way, we propose a dialogical reading of the alleged non constructivity of Kripke’s schema in and we indicate a new path towards another understanding of its constructive content.

We argue that no attempt of reducing meaning to a systematic set of rules, according to which the role of linguistic expressions is to be normatively defined, can be abstracted from an irreducibly decisional compound. By comparing Lorenzen ’s project of building an Ortho-language and Brandom ’s inferentialist take on meaning, we distinguish two ways of acknowledging this fact, while claiming that Lorenzen ’s take is more genuinely constructive, insofar as choices be thought of as genuine features of constructions. It brings into a new perspective the relation between dialogical constructivism and Brouwer ’s intuitionism. Finally we bring up a philosophical argument for the claim that interaction rules should be indexed on players and on their choices, when providing deontic bases to semantics.

We argue that no attempt of reducing meaning to a systematic set of rules, according to which the role of linguistic expressions is to be normatively defined, can be abstracted from an irreducibly decisional compound. By comparing Lorenzen’s project of building an Ortho-languageand Brandom’s inferentialist take on meaning, we distinguish two ways of acknowledging this fact, while claiming that Lorenzen’s take is more genuinely constructive, insofar as choices be thought of as genuine features of constructions. It brings into a new perspective the relation between dialogical constructivism and Brouwer’s intuitionism. Finally we bring up a philosophical argument for the claim that interaction rules should be indexed on players and on their choices, when providing deontic bases to semantics.