Axiomatizing Category Theory in Free Logic
Abstract
Starting from a generalization of the standard axioms for a monoid we present a stepwise development of various, mutually equivalent foundational axiom systems for category theory. Our axiom sets have been formalized in the Isabelle/HOL interactive proof assistant, and this formalization utilizes a semantically correct embedding of free logic in classical higher-order logic. The modeling and formal analysis of our axiom sets has been significantly supported by series of experiments with automated reasoning tools integrated with Isabelle/HOL. We also address the relation of our axiom systems to alternative proposals from the literature, including an axiom set proposed by Freyd and Scedrov for which we reveal a technical issue (when encoded in free logic where free variables range over defined and undefined objects): either all operations, e.g. morphism composition, are total or their axiom system is inconsistent. The repair for this problem is quite straightforward, however.
Keywords
Cite
@article{arxiv.1609.01493,
title = {Axiomatizing Category Theory in Free Logic},
author = {Christoph Benzmüller and Dana S. Scott},
journal= {arXiv preprint arXiv:1609.01493},
year = {2018}
}
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17 pages