Le 5 décembre 2014 en salle D 116 de 17h à 18h30, Theo Kuipers (University of Groningen), donnera une conférence (en anglais) à la Maison de la recherche, 28 rue serpente 75006 Paris. Titre : Models and postulates, enabling a two–sided account of nomic truth approximation Abstract The qualitative theory of nomic truth approximation, presented in my From Instrumentalism to Constructive Realism (2000), in which ‘the truth’ concerns the distinction between nomic, e.g. physical, possibilities and impossibilities, rests on a very restrictive assumption. Fully recognizing two different functions of theories, viz. excluding and representing, this paper drops the restrictive assumption by conceiving theories as tuples of postulates and models, where the postulates claim to exclude nomic impossibilities and the models claim to represent nomic possibilities. Revising theories becomes then a matter of adding or revising models and/or postulates in the light of increasing evidence, captured by a special kind of theories, viz. ‘data-theories’. Achieving empirical progress in this way, assuming the truth of the data-theory, provides good reasons for the abductive conclusion that truth approximation has been achieved as well. In this account, the notions of truth approximation and empirical progress are formally direct generalizations of the earlier ones. However, truth approximation is now explicitly defined in terms of increasing truth-content and decreasing falsity-content of theories, while empirical progress is defined in terms of lasting increasing accepted and decreasing rejected content in the light of increasing evidence. These definitions are strongly inspired by a paper of Gustavo Cevolani, Vincenzo Crupi and Roberto Festa, viz., “Verisimilitude and belief change for conjunctive theories” ( Erkenntnis , 2011).