May 3, 2012 – ENS, 45 rue d'Ulm 75005 Paris
Salle de séminaire du Cirphles, Département de Philosophie (sous-sol du pavillon Pasteur)
Patrick Blackburn (University of Roskilde)
Hybrid Proof Theory
Abstract: In this talk I will discuss and motivate hybrid proof theory. Hybrid proof theory comes in a number of styles: I will try to make clear what is common to them all, but will concentrate on tableaux systems. Although this is a proof on truth theory, a lot of my observations will be semantic, since I believe the heart of hybrid proof theory to be the tools it offers for constructing Robinson diagrams. I shall try to indicate the flexibility this offers by noting both classical applications and recent work on indexicals.
For the most part I shall examine the two basic tools offered by hybrid logic, nominals and @-operators, since these are two most relevant to hybrid proof theory. Time permitting, however, I may talk a little about the more powerful downarrow binder and it proof-theoretic impact.