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Graham Leigh
Professor
Philosophy and Logic unitAbout Graham Leigh
My research concerns the interface of three concepts central to logic: proof, truth and computation. Much of my work examines links between these concepts, such as axiomatic theories of truth, infinitary (and non-wellfounded) notions of proof, and computational content of classical logic. I have published articles on ordinal analysis (proof theory), philosophy of mathematics, intuitionism, and temporal logics, and a monograph The Road to Paradox: A Guide to Syntax, Truth and Modality with Volker Halbach (October 2024).
I joined the logic group as Researcher in 2016 with a Wallenberg Academy Fellowship and was appointed Docent in 2018, Senior Lecturer in 2022 and full professor in Autumn 2024.
For information about our research seminar in logic and activities of our group see our group webpage (external).
My interview with the Wallenberg Foundation: Reflecting on truth with the help of logic.
The Road to Paradox: A Guide to Syntax, Truth and Modality
Co-authored with Volker Halbach (New College, Oxford), The Road to Paradox (CUP) provides a clear and direct introduction to the theory of paradoxes and the Gödel incompleteness theorems. It offers new analyses of the ideas of self-reference, circularity, and the semantic paradoxes, and helps readers to see both how paradoxes arise and what their common features are. The book can be ordered directly from the publisher.
Research projects
- Wallenberg Academy Fellowship Prolongation, 2020. Research project: Taming Jörmungandr: The Logical Foundations of Circularity (2021–2026).
- Wallenberg Academy Fellowship, 2015. Research project: Reflection and Truth (2015–2021).
- VR Starting Grant. Project: Reflecting on Truth and Types (2018–2022).
Research team
- Gianluca Curzi, postdoctoral researcher
- Ivan Di Liberti, postdoctoral researcher
- Anton Pertun Broberg, doctoral student
- Mattias Granberg Olsson, doctoral student
- Giacomo Barlucchi, doctoral student
- Tjeerd Fokkens, doctoral student
- Dominik Wehr, doctoral student
See the logic group homepage to find out about other members.
Preprints and forthcoming work
- Demystifying μ (with Bahareh Afshari and Guillermo Menéndez Turata), January 2024. arXiv: https://arxiv.org/abs/2401.01096
- The limit of recursion in state-based systems (with B. Afshari and Giacomo Barlucchi). Extended abstract in Fixed Points in Computer Science 2024.
- A metapredicative study of μ-arithmetics (with B. Afshari). August 2024.
- Herbrand schemes for first-order logic (with B. Afshari and Sebastian Enqvist), October 2023. Pre-print: https://eprints.illc.uva.nl/id/eprint/2286/.
- Herbrand schemes for cyclic proofs (with B. Afshari and S. Enqvist), December 2023. Pre-print: https://eprints.illc.uva.nl/id/eprint/2292/.
- Uniform interpolation from cyclic proofs (with B. Afshari and G. Menéndez Turata). Full version of the extended abstract in TABLEAUX (2021) with full proofs and application to other modal logics.
- Normal forms for cyclic proofs (with B. Afshari), manuscript. June 2023.
The above manuscripts are available on request.
-
The Road to Paradox: A Guide to Syntax, Truth and
Modality
Volker Halbach, Graham E. Leigh
2024 -
Intuitionistic Master
Modality
Bahareh Afshari, Lide Grotenhuis, Graham E. Leigh, Lukas Zenger
Advances in Modal Logic 2024 - 2024 -
From GTC to RESET : Generating reset proof systems from cyclic proof
systems
Graham E. Leigh, Dominik Wehr
Annals of Pure and Applied Logic - 2024 -
A Compositional Theory of Krivine’s Classical
Realisability
Daichi Hayashi, Graham E. Leigh
Lecture Notes in Computer Science - 2024 -
Cyclic proofs for the first-order
mu-calculus
Bahareh Afshari, S. Enqvist, Graham E. Leigh
Logic Journal of the IGPL - 2024 -
Revisiting the conservativity of fixpoints over intuitionistic
arithmetic
Mattias Granberg Olsson, Graham E. Leigh
Archive for Mathematical Logic - 2024 -
Proof Systems for Two-Way Modal
Mu-Calculus
Bahareh Afshari, Sebastian Enqvist, Graham E. Leigh, Johannes Marti, Yde Venema
Journal of Symbolic Logic - 2023 -
Ill-Founded Proof Systems for Intuitionistic Linear-Time Temporal
Logic
Bahareh Afshari, Lide Grotenhuis, Graham E. Leigh, Lukas Zenger
Automated Reasoning with Analytic Tableaux and Related Methods, 32nd International Conference, TABLEAUX 2023, Prague, Czech Republic, September 18–21, 2023, Proceedings / Editors: Revantha Ramanayake, Josef Urban - 2023 -
A Cyclic Proof System for Full Computation Tree
Logic
Bahareh Afshari, Graham E. Leigh, Guillermo Menéndez Turata
Leibniz International Proceedings in Informatics, LIPIcs Volume 2521, February 2023, EACSL Annual Conference on Computer Science Logic, CSL 2023, Warsaw, 13 February 2023 through 16 February 2023 - 2023 -
From Paradox to
Truth
Graham E. Leigh
Özgün, A., Zinova, Y. (eds) Language, Logic, and Computation. TbiLLC 2019. Lecture Notes in Computer Science, vol 13206 - 2022 -
Lyndon Interpolation for Modal
μ-Calculus
Bahareh Afshari, Graham E. Leigh
Language, Logic, and Computation, 13th International Tbilisi Symposium, TbiLLC 2019, Batumi, Georgia, September 16–20, 2019, Revised Selected Papers / editors: Aybüke Özgün, Yulia Zinova - 2022 -
The Copernican Multiverse of
Sets
Paul Kindvall Gorbow, Graham E. Leigh
The Review of Symbolic Logic - 2022 -
Uniform Interpolation from Cyclic Proofs: The Case of Modal
Mu-Calculus
Bahareh Afshari, Graham E. Leigh, Guillermo Menéndez Turata
Automated Reasoning with Analytic Tableaux and Related Methods, 30th International Conference, TABLEAUX 2021, Birmingham, UK, September 6–9, 2021, Proceedings / Anupam Das, Sara Negri (eds.) - 2021 -
Herbrand's theorem as higher order
recursion
Bahareh Afshari, Stefan Hetzl, Graham E. Leigh
Annals of Pure and Applied Logic - 2020 -
An infinitary treatment of full
mu-calculus
Bahareh Afshari, Gerhard Jäger, Graham E. Leigh
Lecture Notes in Computer Science 26th International Workshop, WoLLIC 2019, Utrecht, The Netherlands, July 2-5, 2019, Proceedings / editors: Iemhoff, Rosalie, Moortgat, Michael, de Queiroz, Ruy - 2019 -
Axiomatic Theories of
Truth
Volker Halbach, Graham E. Leigh
Stanford Encyclopedia of Philosophy - 2018 -
Herbrand’s Theorem as Higher Order
Recursion
Bahareh Afshari, Stefan Hetzl, Graham E. Leigh
2018 -
Truth is
Simple
Leon Horsten, Graham E. Leigh
Mind - 2017 -
Cut-free completeness for modal
mu-calculus
Bahareh Afshari, Graham E. Leigh
32nd Annual ACM/IEEE Symposium on Logic in Computer Science (LICS), 20-23 June 2017, Reykjavik Iceland - 2017 -
Herbrand confluence for first-order proofs with
Π2-cuts
Bahareh Afshari, Stefan Hetzl, Graham E. Leigh
Concepts of Proof in Mathematics, Philosophy, and Computer Science / Dieter Probst, Peter Schuster (eds.) - 2016 -
Herbrand's theorem
revisited
Bahareh Afshari, Stefan Hetzl, Graham E. Leigh
Proceedings of Applied Mathematics and Mechanics. Joint 87th Annual Meeting of the International Association of Applied Mathematics and Mechanics (GAMM) and Deutsche Mathematiker-Vereinigung (DMV), Braunschweig 2016; Editors: V. Bach and H. Fassbender - 2016 -
On the Herbrand content of
LK
Bahareh Afshari, Stefan Hetzl, Graham E. Leigh
Proceedings Sixth International Workshop on Classical Logic and Computation (CL&C16). Porto, Portugal , 23th June 2016 - 2016 -
Reflecting on
Truth
Graham E. Leigh
IfCoLog Journal of Logics and their Applications - 2016 -
Finitary Proof Systems for Kozen’s
μ
-
Circular proofs for the modal
mu-calculus
Bahareh Afshari, Graham E. Leigh
Proceedings of Applied Mathematics and Mechanics. Joint 87th Annual Meeting of the Gesellschaft für Angewandte Mathematik und Mechanik, held 7 – 11 March 2016 at TU Braunschweig, Germany. - 2016 -
Herbrand disjunctions, cut elimination and context-free tree
grammars
Bahareh Afshari, Stefan Hetzl, Graham E. Leigh
Leibniz International Proceedings in Informatics, LIPIcs - 2015 -
Some Weak Theories of
Truth
Graham E. Leigh
Unifying the Philosophy of Truth - 2015 -
Conservativity for theories of compositional truth via cut
elimination
Graham E. Leigh
Journal of Symbolic Logic - 2015 -
Axiomatic theories of
truth
Graham E. Leigh, Volker Halbach
Stanford Encyclopedia of Philosophy (Summer 2014 Edition) - 2014 -
On closure ordinals for the modal
μ-calculus
Bahareh Afshari, Graham E. Leigh
Leibniz International Proceedings in Informatics, LIPIcs - 2013 -
A proof-theoretic account of classical principles of
truth
Graham E. Leigh
Annals of Pure and Applied Logic - 2013 -
Axiomatic truth, syntax and metatheoretic
reasoning
Graham E. Leigh, Carlo Nicolai
Review of Symbolic Logic - 2013 -
Revision
Revisited
Leon Horsten, Graham E. Leigh, Hannes Leitgeb, Philip Welch
The Review of Symbolic Logic - 2012 -
The Friedman-Sheard programme in intuitionistic
logic
Graham E. Leigh, Michael Rathjen
Journal of Symbolic Logic - 2012 -
A proof-theoretic account of classical principles of truth (extended
abstract)
Graham E. Leigh
Numbers and truth, Göteborg, Sweden, October 19-21, 2012 - 2012 -
An ordinal analysis for theories of self-referential
truth
Graham E. Leigh, Michael Rathjen
Archive for Mathematical Logic - 2010 -
Proof-theoretic investigations into the Friedman-Sheard theories and other theories of
truth
Graham E. Leigh
2010 -
Five papers on axiomatic theories of
truth
Graham E. Leigh
Bulletin of Symbolic Logic - 2010