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On a definition of finite cardinals in an arbitrary topos. (Spanish) Zbl 0653.18003

This paper presents a definition of finite cardinal in an arbitrary topos, using extensional relations, which turns out to be equivalent to the usual (i.e. Kuratowski-finite, decidable and linearly ordered objects). It is also shown that the full subcategory of finite cardinals forms a topos with the axiom of choice.
Reviewer: M.Bunge

MSC:

18B25 Topoi
03E25 Axiom of choice and related propositions
03E10 Ordinal and cardinal numbers

Keywords:

finite cardinal
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