25 January 2010
REPORT: Formal Philosophy Seminars
Posted by Rasmus Rendsvig under: Conference and workshop reports; Dynamic Logic; Modal Logic .
Sebastian Sequoiah-Grayson continues to reports on the Formal Philosophy Seminars hosted by the Formal Epistemology Project at the University of Leuven:
Sonja Smets – Groningen (joint work with Alexandru Baltag from the Oxford Comlab) talked to us about “Merging beliefs by talking your way into agreement”. The issue concerns modeling the the phenomenon of doxastic agreement amongst groups of agents. The actual process brining about such agreements is, of course, the the exchange of information. Taking the goal of such informational exchange to be total agreement amongst the agents in the group, various rules for the “exchange game”, such as public communication, sincerity, and persuasiveness were laid down. The hard (and fun!) work turned on the properties required by the various dynamic belief-merging operations. Some of these operations operate on particular beliefs, and others on entire doxastic structures! Question time went overtime, and this was one of my favourite FPS talks so far.
Toby Meadows provided a tableau system and a completeness proof for a revised version of Carnap’s semantics for quantified modal logic. Recall that for Carnap, a sentence is possible if it is true in some first order model. This is a fundamentally semantic conception of modality. As with second order logic, no sound and complete proof theory can be provided for this semantics. Arguably this contributed to the disappearance of Carnapian modal logic from contemporary philosophical discussion. The proof theory proposed by Toby comes much closer to Carnap’s semantic vision and provides an interesting counterpoint to mainstream modal logic.
Marie Duzi took us from extensions, via intensions, to hyperintensions! The procedural semantic framework that she develops (Tichy’s Transparent Intensional Logic) makes procedures first class entities. The point os to concretely realise Frege’s Modes of Presentation, and give us a way to semantically individuate necessary, a priori truths. In this presentation, Marie concentrated on the phenomena of definite descriptions, as framed by the debate between Russell and Strawson. Marie mounted a careful argument for Donellen’s claim that sentences of the for “The F is a G” are ambiguous. However, she argued that theor ambiguity does not concern a shift in meaning of the definite description ‘the F’, but that it concerns different “topic-focus” artuculations of such sentences. This analysis was parsed in terms of differing suppositions are involved in the relevant interpretations, but where the one and the same meaning occurs. In case anyone thought that such a distinction turns on pragmatic as opposed to semantic considerations, Marie had some careful arguments for why it is that topic-focus articulation is a concretely semantic beast.
Next time: Katya Tentori (29/01/10) and Jan Sprenger (05/02/10)!
Photos of fun at FPS and other events at FEP may be found here: http://formalphilosophy.org/gallery
Sebastian Sequoiah-Grayson
Formal Epistemology Project
Leuven
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