Benoît Mandelbrot and Marcel-Paul Schützenberger first met at the Institut Poincaré in Paris in the 1950s, when both were working on topics in the then novel field of information theory. Their paths crossed again at the other end of the Atlantic on the East Coast where they were drawn into discussions on formal models of language. This was an important topic in the U.S. because these models could be useful for automatic translation, and for automatic coding of information and of programs for digital computers. In the late 1950s, a vivid debate raged whether probabilistic models or rather grammatical or rule-based models were appropriate for describing (natural) language, with notably Noam Chomsky and his students attacking the probabilistic approach. As Mandelbrot arrived in the U.S., the probabilistic model of language he had developed in his PhD became part of the discussion. Also Schützenberger got involved in the debate with his early work on coding theory. Eventually, Chomsky's arguments against probabilistic models would prevail. As a result, Mandelbrot's research went into a slightly different direction that would bring him to fractal geometry, whereas Schützenberger, via his frequent visits to the U.S., became one of the architects of the mathematics behind formal languages and coding theory.[-]

In his 1947 essay, Tjalling Koopmans criticized the development of an empirical science that had no theoretical basis, what he referred to as measurement without theory. The controversy over the status of relations based on mere statistical inference has not ceased since then. Instead of looking for the contemporary consequences, however, I will inquire into its early beginnings. As early as the 1900s, Walras, Pareto and Juglar exchanged views on the status of theory and its relation to economic data. These private exchanges acquired the status of scientific controversy in the aftermath of the First World War, with the dissemination of Pareto's work. It is precisely this moment that I will try to grasp, when engineers began to read and write pure economic treatises, questioning the relation between theory and empirical problems, the nature of their project and the expectations that the subsequent development of economics has tried to fulfill.

Cournot Centre session devoted to the transformations that took place in mathematical economics during the interwar period.[-]

In order to explore the advances made on the economic issue of business cycles, I will present the work of the American economist Henry Ludwell Moore, who published four works on the question between the years 1911 and 1923. Within this framework, I will introduce several issues, such as the duality of empirical and theoretical approaches, the causal and semiological interpretations of the correlation, the notion of the ceteris paribus law in economics, the notion of non-probabilistic statistical mathematics, the development of the notion of the dynamic model at the end of the 1920s, the diverse analysis techniques of chronological series and their artefacts. I will also make reference to the contributions of other actors in this field.

Cournot Centre session devoted to the transformations that took place in mathematical economics during the interwar period.[-]

Andreï Kolmogorov est un mathématicien russe (1903-1987) qui a apporté des contributions frappantes en théorie des probabilités, théorie ergodique, turbulence, mécanique classique, logique mathématique, topologie, théorie algorithmique de l'information et en analyse de la complexité des algorithmes. Alexander Bufetov, Directeur de recherche CNRS (I2M - Aix-Marseille Université, CNRS, Centrale Marseille) et porteur local de la Chaire Jean-Morlet (Chaire Tamara Grava 2019 - semestre 1) donnera une conférence sur les contributions exceptionnelles et la vie dramatique d'un grand génie du XXe siècle.[-]