# Overview

The workshop aims at bringing together two EUROCORES / LogICCC projects, DiFoS and LoMoReVI, to discuss several aspects of the relationship between the notions of 'proof' and 'dialogues'.

The two projects already organised (together with LcpR) the DIPLEAP workshop, in which the notions of dialogue and proof were in focus. While DIPLEAP stressed the empirical aspects of the notions of inference and of interaction underlying proofs and dialogues, the workshop "Proof and Dialogues" (ProDi) aims at displaying the theoretical questions raised by a comparison of the two from a logical and philosophical standpoint. Thus ProDi is a way of developing the established and reciprocally acknowledged interest of the two projects involved.

The notion of proof is one of the cornerstones of logic. Proof theory is a discipline whose development contributed in an essential manner to our understanding of what is logic. The interest for logical characterisations of the notion of dialogue in the spirit of Lorenzen's work has, on the other hand, only recently spread in the literature. Dialogues were introduced in order to overcome some difficulties that the project of characterising the meaning of logical constants in proof-theoretic terms had to face. One of the main goals of DiFoS is the development of a comparison between proof-theoretic semantics and the dialogical approach to logic. The comparison is developed by looking at the differences in the conceptions of our understanding of the functioning of logical constants the two perspectives yield to.

Among the main aims of LoMoReVI is that of proposing fuzzy logics as a paradigmatic tool for dealing with the notion of vagueness. The proof theory of fuzzy logics proved to be an interesting field of research, and the dialogical setting is being used in offering new possibilities of characterising in an original way the notion of vagueness at the core of 'fuzzy thought'. The workshop appears as the ideal setting for discussing how a dialogical characterisation of fuzzy logics can be worked out and which advantages and disadvantages it has, when compared to a proof-theoretic one.

Hence, it is expected that the workshop will yield new insights to both projects involved.

The workshop is organised by prof. Peter Schroeder-Heister (DiFoS – Tübingen) and prof. Christian Fermüller (LoMoReVI – Wien). Local organisers are Thomas Piecha and Luca Tranchini.

**External Experts**:

- Andreas R. Blass (University of Michigan)
- Laurent Keiff (University of Lille 3)
- Alain Lecomte (University of Paris 8)
- Kuno Lorenz (Universität des Saarlandes)
- George Metcalfe (University of Bern)
- Shahid Rahman (University of Lille 3)
- Helge Rückert (University of Mannheim)
- Morten Heine Sørensen (Formalit)
- Tero Tulenheimo (University of Lille 3)