In this paper, we study dialogue as a game, but not only in the sense in which there would exist winning strategies and a priori rules. Dialogue is not governed by game rules like for chess or other games, since even if we start from a priori rules, it is always possible to play with them, provided that some invariant properties are preserved. An important discovery of Ludics is that such properties may be expressed in geometrical terms. The main feature (...) of a dialogue is “convergence”. Intuitively, a dialogue “diverges” when it stops prematurely by some disruption, or a violation of the tacit agreed upon conditions of the discourse. It converges when the two speakers go together towards a situation where they agree at least on some points. As we shall see, convergence may be thought of through the geometrical concept of orthogonality . Utterances in a dialogue have as their content, not only the processes (similar to proofs) which lead to them from a monologic view, but also their interactions with other utterances. Finally, any utterance must be seen as co-constructed in an interaction between two processes. That is to say that it not only contains one speaker’s intentions but also his or her expectations from the other interlocutor. From our viewpoint, discursive strategies like narration , elaboration , topicalization may derive from such interactions, as well as speech acts like assertion, question and denegation. (shrink)

Is it possible to characterize the notion of proof in terms of acts, without focusing on a specific domain of application and a specific linguistic formalization of it? This is the question that this paper addresses through a comparative analysis between two logicians who reflected on this issue: Kurt Gödel and Jean-Yves Girard. A comparative analysis of their respective theoretical frames, their respective results, the similarities and the differences between their methodological assumptions is proposed. More specifically, the aim of the (...) paper is to compare Gödel’s notion of absolute proof and Girard’s notion of Ludic from their common core: a conception of proof in terms of acts. (shrink)

We give the precise correspondence between polarized linear logic and polarized classical logic. The properties of focalization and reversion of linear proofs are at the heart of our analysis: we show that the tq-protocol of normalization for the classical systems and perfectly fits normalization of polarized proof-nets. Some more semantical considerations allow us to recover LC as a refinement of multiplicative.

The aim of this paper is to define a λ-calculus typed in aMixed (commutative and non-commutative) Intuitionistic Linear Logic. The terms of such a calculus are the labelling of proofs of a linear intuitionistic mixed natural deduction NILL, which is based on the non-commutative linear multiplicative sequent calculus MNL [RuetAbrusci 99]. This linear λ-calculus involves three linear arrows: two directional arrows and a nondirectional one (the usual linear arrow). Moreover, the -terms are provided with seriesparallel orders on free variables. We (...) prove a normalization theorem which explicitly gives the behaviour of the order during the normalization procedure. (shrink)

We focus in this paper on the potential uses of Ludics, a logical framework based on recent developments in proof theory, for modeling natural language dialogues. The aim is to be able to grasp and to account for some aspects of incoherence in discourses. Among the properties relevant for studying dialogues, two features of Ludics are of interest for our purpose: the duality of viewpoints of two interlocutors as well as the possibility of ruptures. We illustrate first the potential usefulness (...) of such a model for accounting and analyzing incoherence in dialogues due to cultural gap. We then focus on dialogues with schizophrenic individuals to try to answer the following questions: to what extent does incoherence play a role in schizophrenic discourse? And, would a more precise characterization of “non-standard” rationality help explain the range of potential complications of schizophrenia? (shrink)

The aim of this paper is to extend the classical sequent calculusLC to the second order. This task is realized by a semantical approach mixing the correlation spaces semantics ofLC on the one hand, and the analogy with the interpretation of systemF in coherent spaces on the other hand. This relies on the introduction of a new semantical object:noetherian correlation spaces.From the semantics we deduce the syntax of the second order classical sequent calculusLC2.