NOL Seminar with Henry Towsner
published: 2026-01-16
event date:
2026-01-26
The Nordic Online Logic Seminar
is organised monthly over Zoom, with expository talks on topics of interest for
the broader logic community. The seminar is open for professional or aspiring
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Date Monday, 26 January 2026 at 16:00 CET (UTC+1) on Zoom
Speaker Henry Towsner (Associate Professor, University of Pennsylvania)
Title What proofs can be
Abstract
Throughout proof theory, proofs are often taken to be well-founded (often
finite) trees of inferences. Theories of inductive definitions, among other
theories, bump up against the limitations of this perspective, and a variety of
formalisms have been used to push beyond this - Girard’s beta-proofs,
non-well-founded proofs, proofs-as-functions. We briefly describe some features
of these approaches, the way these perspectives are essentially equivalent, and
the way well-foundedness reasserts itself as a core property of proofs.