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arXiv · 1803.02472

Abstraction Principles and the Classification of Second-Order Equivalence Relations

Sean C. Ebels-Duggan
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Abstract

This paper improves two existing theorems of interest to neo-logicist philosophers of mathematics. The first is a classification theorem due to Fine for equivalence relations between concepts definable in a well-behaved second-order logic. The improved theorem states that if an equivalence relation $E$ is defined without non-logical vocabulary, then the bicardinal slice of any equivalence class---those equinumerous elements of the equivalence class with equinumerous complements---can have one of only three profiles. The improvements to Fine's theorem allow for an analysis of the well-behaved models had by an abstraction principle, and this in turn leads to an improvement of Walsh and Ebels-Duggan's relative categoricity theorem.

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BibTeXRIS

Sean C. Ebels-Duggan. 2018-03-06. Abstraction Principles and the Classification of Second-Order Equivalence Relations. https://doi.org/10.1215/00294527-2018-0023

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