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arXiv · 2408.13769

Suszko's Thesis and Many-valued Logical Structures

Sayantan Roy·Sankha S. Basu·Mihir K. Chakraborty
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Abstract

In this article, we try to formulate a definition of ''many-valued logical structure''. For this, we embark on a deeper study of Suszko's Thesis ($\mathbf{ST}$) and show that the truth or falsity of $\mathbf{ST}$ depends, at least, on the precise notion of semantics. We propose two different notions of semantics and three different notions of entailment. The first one helps us formulate a precise definition of inferentially many-valued logical structures. The second and the third help us to generalise Suszko Reduction and provide adequate bivalent semantics for monotonic and a couple of nonmonotonic logical structures. All these lead us to a closer examination of the played by language/metalanguage hierarchy vis-á-vis $\mathbf{ST}$. We conclude that many-valued logical structures can be obtained if the bivalence of all the higher-order metalogics of the logic under consideration is discarded, building formal bridges between the theory of graded consequence and the theory of many-valued logical structures, culminating in generalisations of Suszko's Thesis.

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Sayantan Roy, Sankha S. Basu, Mihir K. Chakraborty. 2026-03-01. Suszko's Thesis and Many-valued Logical Structures. https://arxiv.org/abs/2408.13769

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