NOL Seminar with David Makinson
published: 2025-10-16
event date:
2025-10-27
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, 27 October 2025 at 16:00 UTC+1 on Zoom
Speaker Monday, 29 September 2025 at 16:00 CEST (UTC+2) on Zoom
Title Decomposing Arrows with Parity
Abstract
The idea of articulating a propositional logic that adds a relevance-sensitive
implication connective to the usual truth-functional ones has been approached in
many ways, e.g. using axioms and derivation rules, natural deduction systems,
possible worlds or states equipped with relations or operations, algebraic
structures, consecution systems etc. None are very satisfactory. In the 1970s,
semantic decomposition trees (aka truth-trees, semantic tableaux, analytic
tableaux) were briefly considered, but they did not get far and were swept away
by the tsunami of Routley/Meyer possible worlds with ternary relations. We renew
that approach using a notion of parity for the branches of a tree or,
alternatively, an even more global one of sibling-parity for the entire tree.
There are some nice results and, above all, some big open questions.