Logic List Mailing Archive

CfPart: ExtenDD Seminar Series on Definite Descriptions, starting 25 October 2023, online

Dear Listmembers,

as part of Prof. Andrzej Indrzejczak’s ERC Advanced Grant ExtenDD: Coming to Terms (project number: 101054714) held at the University of Lodz, Poland, we will hold a seminar on the topic of the grant, the proof theory of definite descriptions and other term forming operators, to which we are inviting interested participants.

The Project
The project is concerned with two areas which so far have rarely come together: complex terms and proof theory. ExtenDD focuses on definite descriptions as the most important and troublesome singular terms and on sequent calculus and its generalisations as the most important tools of modern proof theory.
Since Russell’s ‘On Denoting’, regarded as a paradigm of analytic philosophy, definite descriptions occupy a central place in philosophical research and many deep and detailed studies have been carried out. The second half of the 20th century saw the development of new approaches to this phenomenon based on non-classical logics, in particular free logic in which, contrary to Frege’s and Russell’s classical logic, it is not assumed that every term refers. Yet despite the long history of research into definite descriptions, a paradigm of formal logic has so far rarely been applied to them: proof theory. The methods developed by Gentzen, in particular those relating to his sequent calculus, provide the means for the deepest study of proofs and their properties. Yet only a small effort has so far been put into the adequate treatment of definite descriptions in this framework. The same counts for other complex singular terms such as set abstracts and number operators. ExtenDD fills this important gap in research.
Applying the methods of proof theory to definite descriptions is profitable to both sides. Competing theories of definite descriptions and complex terms in general, their advantages and shortcomings, are shown in a new light. The behaviour of complex terms needs subtle syntactical analysis and requires enriching the toolkit of proof theory. ExtenDD deals with both challenges: it develops formal theories of definite descriptions and modifies the machinery of proof theory to cover new areas of application. The realisation of ExtenDD affects significantly the field of proof theory, automated deduction and philosophy of language.

The Seminar Series
We aim to hold a seminar roughly every two weeks on Wednesdays from 4 to 6pm CET during term time. It will be held online on Teams. There will be speakers from amongst the ExtenDD team as well as external speakers.

The series kicks off on the 25. October

25th October:  Andrzej Indrzejczak: Constructive Proof of the Craig Interpolation Theorem for Russellian Logic of Definite Descriptions

15th November: Andrzej Indrzejczak: Russellian Logic of Definite Descriptions and Anselm's God

29th November: Przemysław Wałęga: Bisimulation for propositional modal logic with definite descriptions

13th December: Nils Kürbis: Some Thoughts on Formalising Definite Descriptions with Binary Quantifiers in Modal Logic

The first, tentative dates for next year are 10th and 14th of January and 7th of February, with speakers to be announced.

If you wish to participate, please email Yaroslav Petrukhin ( yaroslav.petrukhin@gmail.com<mailto:yaroslav.petrukhin@gmail.com> ) to register your interest. You’ll then receive a link to the Teams Meeting and regular updates on the seminar series.

With the very best wishes,


Nils Kürbis
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