Weihnachts-Logikkolloquium

20. Dezember 2002

Zeitplan

Philosophisches Seminar
Universität Göttingen
Humboldtallee 19
Seminarraum PH 133

Alle Interessierten sind herzlich eingeladen, an dem Kolloquium teilzunehmen.

Abstracts

Leon Horsten (joint work with Steven Delvaux and Rafael De Clercq):

Best equivalence-approximations and criteria of identity

Let there be given a finite graph G and a finite equivalence relation E, also considered as a graph. We measure the degree of closeness of E to G by the sum of the number of edges of G¤E and the number of edges of E¤G. It is shown that the problem of finding a closest equivalence relation to a given graph G is NP-complete. The extension of the concept of closest equivalence relation to infinite graphs is also discussed. Our technical observations are then brought to bear on philosophical issues relating to criteria of identity for empirical objects, properties and relations. These issues date back to Carnap’s Aufbau and have more recently been discussed by Timothy Williamson.

Hannes Leitgeb:

What Truth Depends on

The guiding idea of my talk is to replace Tarski's Convention T as an adequacy
criterion for theories of truth by the following specification of it:

Convention Td: a theory of truth is materially adequate if and only if every biconditional

Tr("A")<-> A

is derivable from it, where A is any sentence of the object language which depends on non-semantical facts only. The object language is in turn allowed to contain the truth predicate Tr.

But what is meant by 'depends on non-semantical facts only'? In order to answer this question we introduce a notion of semantical dependence holding between sentences and sets of sentences and we study its properties. On the basis of this dependence relation, we are able to define dependence on non-semantical facts only, and we can show that Convention Td may indeed be satisfied despite the presence of vicious selfreferentiality or ungroundedness in the object language.

Philip Welch:

General Frameworks for Possible Worlds, Truth-at-a-world and Tarskian hierarchies

We look at some recent research into the kinds of abstract orderings that support such hierarchies and frames. We report on some unpublished work of Shavrukov and Solovay that has import in this area.

last change: 13 May, 2006

e-mail address (please replace "0" by the usual "@" symbol): volker.halbach at philosophy.oxford.ac.uk