Yvon Gauthier

Cet article propose une nouvelle approche dans l'analyse et l'interprétation des théories physiques. La théorie des modèles ou sémantique ensembliste est rejetée au profit d'une syntaxe ou théorie des démonstrations qui s'attache d'abord à la structure formelle d'une théorie physique. On donne plusieurs exemples d'une théorie de la preuve , exemples qui relèvent surtout de la mécanique quantique et qui vont dans le sens de la thèse principale de l'auteur : la surdétermination de la théorie physique par sa structure mathématique.This paper deals with a novel approach in the interpretation of physical theories. Model theory or set-theoretical semantics is here replaced by a proof-theoretical analysis which is applied to the formal structure of a physical theory. Many examples are given, mainly in Quantum Mechanics, which aim at illustrating the main thesis of the paper: that a physical theory is over-determined by its mathematical structure and cannot be defined by the class of its empirical structures

Hermann Weyl as a founding father of field theory in relativistic physics and quantum theory always stressed the internal logic of mathematical and physical theories. In line with his stance in the foundations of mathematics, Weyl advocated a constructivist approach in physics and geometry. An attempt is made here to present a unified picture of Weyl's conception of space-time theories from Riemann to Minkowski. The emphasis is on the mathematical foundations of physics and the foundational significance of a constructivist philosophical point of view. I conclude with some remarks on Weyl's broader philosophical views.

This paper aims at a logico-mathematical analysis of the concept of chaos from the point of view of a constructivist philosophy of physics. The idea of an internal logic of chaos theory is meant as an alternative to a realist conception of chaos. A brief historical overview of the theory of dynamical systems is provided in order to situate the philosophical problem in the context of probability theory. A finitary probabilistic account of chaos amounts to the theory of measurement in the line of a quantum-theoretical foundational perspective and the paper concludes on the non-classical internal logic of chaos theory. Finally, deterministic chaos points to a philosophy which asserts that chaotic systems are no less measurable than other physical systems where predictable and non–predictable phenomena intermingle in a constructive theory of measurement.

Le réalisme se porte mal: des philosophes comme Putnam ou van Fraassen qui naguère encore défendaient des points de vue à tout le moins apparentés au réalisme proposent des thèses anti-réalistes ou qui sont aux antipodes du réalisme métaphysique. Et ceux qui tiennent encore au réalisme le voilent prudemment. Quant au réalisme critique de Popper et des poppériens, il est relégué aujourd'hui au rôle d'une thèse historique sur le développement rationnel de la science que contredit la doctrine kuhnienne. Reste le réalisme naïf.

My discussion centers around Ulrich Kohlenbach's Applied Proof Theory: Proof Interpretations and their Use in Mathematics [21 ] which appears as a major work in the "proof mining project" of recent proof theory. The emphasis is on the tradition of proof theory originating with Hilbert and his motivations. I examine also Hilbert's Kroneckerian inspiration and I maintain that Hilbert's programme is the continuation of Kronecker's programme by logical and metamathematical means. I conclude that despite Kreisel's proposal of a shift of emphasis in traditional proof theory, Hilbert's original proof-theoretical ideal is still alive and proof mining is in the purview of Hilbert programme. © 2011 Elsevier B.V., All rights reserved.