Séance du 13 décembre 2012

On Abramsky's game semantics

Pierre Cardascia

13 décembre, 13h-15
Attention : salle F0.42 (Maison de la Recherche)


(titre provisoire)

Séance du 15 novembre 2012

A Modal Approach to Theoretical Terms

Matthieu Gallais

15 novembre, 13h-15h
Maison de la recherche, salle F1.07


Abstract:
  The purpose of my presentation is to explain some issues related to the understanding of scientific theories as intrinsically modal constructions. In particular, how can one identify an actual object with a theoretical identity if, for example, that entity has idealized properties according to the theory in which it has been defined? I will suggest a solution which consists in using Hintikka's concept of world-line. The aim is not to replace the original individuating functions, but to develop a second-order function to study the behaviour of properties across possible worlds. Finally, I will show the usefulness of that idea concerning the traditional issue of theoretical terms by revisiting their definitions thanks to world-lines.

Séance du 8 novembre 2012

Game-Theoretical Semantics Generalized

Tero Tulenheimo

8 novembre, 13h-15h
Maison de la Recherche, salle F1.07


Abstract:
   I present a way of generalizing Game-Theoretical Semantics, by enriching positions of games with a new component called `mode'. In connection with certain languages (including IF logic) classical negation becomes game-theoretically interpretable. Ways of capturing certain fragment of higher-order logic in this setting are discussed.

Séance du 18 octobre 2012

Au programme de cette première séance de l'année 2012-2013 :

Learning and inferences: a logical model of a cognitive agent

Christel Grimaud

18 octobre, 13h-15h.
Maison de la Recherche, salle F1.07


Abstract:
     In my talk I will present what I think is a suitable logic for modelling the inferences and learning processes of a cognitive agent.
     First, I will recall the theoretical background of belief revision and non-monotonic inferences. The most influential model for belief revision is the AGM model, called after its three originators, Carlos Alchourron, Peter Gardenfors and David Makinson. However this model suffers from a well-known problem, which is that it doesn't allow iteration. I will recall where does this problem come from, and will consequently argue that the AGM model is not suitable for modelling an agent's learning. In the field of non-monotonic logic, an important account was given by Sarit Kraus, Daniel Lehmann and Menachem Magidor, with a family of logics known as KLM logics or inference relations. Amongst there are the so-called rational consistent inference relations, which have been shown to be strictly equivalent to AGM's belief revision. I will recall this result and will argue that learning must be seen not as a revision of beliefs sets as in the AGM model, but rather as revision of an agent's dispositions to infer. That is, that what are to be revised are the very inference relations. There have been a few attempts in this sense, but non of these seems to be fully satisfying. I will argue that this comes from the fact that rational consistent relations are not the ones which are to be revised, but rather the inference relations of a more general class, which has not been characterized yet. I will present this class of inference relations, and will show how these relations can be revised in a natural and intuitive manner. Then I will present my own attempt to caraterize it.

Séance du 12 avril

Jeudi 12 avril, 11h-13h

Salle Corbin

Abramsky's game semantic and dialogic

Pierre Cardascia

Abstract:

My first presentation in this GdT, "Vers une définition de stratégie sans hypothèse métalogique", began by questioning a metaphoric sentence from Girard: "Game semantics is a fighting sport; but a polite and civilised one: there is an arbiter who prevents nasty moves and bad behaviours. Ludics is more like wrestling: we knocked down the arbiter." I tried to interpret this "arbiter" as "metalogical hypotheses", I exposed some ideas about what should be a strategical behaviour in this context, inspired by different analyses of the Nim games (classic MeX-calculus, categorical analysis, question of the meaning of the cheat.

In my second intervention, "Formalism towards strategical behaviours", I showed the formal problems underlying the precedent talk: materialized players, variable number of players, both legal and illegal moves are possible... It gives us a "research plan". Then I finished by suggesting a "convergence" between the representation of dialogues and the representation of the trace in Abramsky's game semantics (with arenas etc).

For this session, "Abramsky's game semantics and dialogic", I will do more than suggesting, I will construct algorithms of translation between them, thanks to one little but new theorem of "arena-making dialogue":

For each set of particle rules , for each game, there exists a concrete justification [legitimation] such that this game forms a justified sequence of moves in an arena

It shall allow us to implement new results in dialogic (from categorial GS: Abramsky, Hyland, Ong ...) and fulfill the desiderata of the precedent talk. But we won't go too fast: to prove this theorem, I shall present and discuss the concepts of Abramsky's GS.

Séance du 5 avril

Jeudi 5 avril, 11h-13h
Salle D. Corbin

A Dynamic Logic of Interrogative Inquiry

Yacin Hamami

(Vrije Universiteit Brussel)

Abstract :

In this talk, I will propose a dynamic-epistemic analysis of the different epistemic operations constitutive of the process of interrogative inquiry, as described by Hintikka's Interrogative Model of Inquiry (IMI). I will develop a dynamic logic of questions for representing interrogative steps, based on Hintikka's treatment of questions in the IMI, along with a dynamic logic of inferences for representing deductive steps, based on the tableau method. I will then merge these two systems into a dynamic logic of interrogative inquiry which articulates a joint treatment of questions and inferences, providing thereby a unified framework representing the informational dynamics of interrogative inquiry.

I will provide sound and complete axiomatic systems for the three dynamic logics that I introduce, I will compare the framework with existing approaches and I will finally propose several directions for further works. This work is meant as a first step towards linking the IMI with the field of dynamic logics of information and rational agency.

Séance du 15 mars

Jeudi 15 mars, 11h-13h.

Salle Corbin

Husserl on Intentional Attitudes

Giuliano Bacigalupo

Abstract:

In my presentation, I start by addressing the semantics developed by Husserl in his lecture Alte und Neue Logik (1908/9), which may be labelled as "sheres semantics". In the second part, I rely on this semantics as an interpretation grid for Husserl's analysis of intentional attitudes in Ideen I (1913) and argue for an interpretation of the noema as reference to non-actual objects or, what is tantamount to the same, to a non-actual sphere. Thirdly, I address Husserl's discussion of a prosteriori identities in the third section of Ideen I and how this bears on the previous discussion, especially on the notion of object simpliciter. Finally, I turn on the vexed question wether Husserl is a Fregean.

Séance du 16 février

Jeudi 16 février, 11h-13h

Salle Corbin

Playing with or without a list of announcements?

Sébastien Magnier

Abstract:

In a previous presentation, I have argued that a public announcement does not correspond to any conditional connectives. But in fact there are algorithms of translation that turn any public announcement in a conditional way. These translations do not yield an immediate material implication of annoucement propositions. They give us complex or embedded conditionals whose complexity directly depends of the post-condition of the announcement operator. Now, our aim is to compare the dialogues with those propositions (the one with the public announcement operator on the one hand and its corresponding translation on the other hand). As we shall see, such a study underlines the meaning of the list of announcements. This list represents the story of the commitment of the players. It emphasizes the two distinct levels: play and strategy level which occur in the dialogical framework. The comparison between them also suggests some improvements of the rule (SR-A.1) that will probably entail a weakening of the formal rule.

Séance du 2 février 2012

Jeudi 2 février, 11h-13h

Against the so-called “fictional nature” of Law

Juliele Sievers

Abstract:

In my presentation I will try once more to attack the notion of fiction in Law, this time by using some elements of Amie Thomasson’s artefactual theory and Hans Vaihinger’s Philosophy of As-If. Since the first lecture of those works seems to give the idea that norms have the same characteristics of fictions, I will present some arguments against this interpretation. One of them refers to the multiplicity of interpretations of the term “fiction”, which often leads to confusion in its use. Starting by comprehending that the definition of fiction in Literature, in Science and in Law has totally different aspects will lead us to a strong consequence: that the presence of this term in a prescriptive ambit it’s in fact a misuse of it (and we will also understand why this improper practice is nevertheless so widely spread).

Attention : les horaires du GdT ont changé (voir le message ci-dessous).

Dates et Horaire des séances à venir

Changement de semestre et d'emplois du temps obligent, les séances du Groupe de Travail auront désormais lieu à des horaires différents.

Les séances auront lieu de 11 heures à 13 heures les jeudis suivants :

2 février, 16 février.

8 mars, 22 mars.

5 avril, 12 avril.

10 mai, 24 mai.

7 juin, 28 juin.