Numerology in topoi

Peter Freyd

This paper studies numerals, natural numbers objects and, more generally, free actions, in a topos. A pre-numeral is a poset with a constant, 0, and a unary operation, s, such that:
x\leq y implies sx \leq sy
x\leq sx
A numeral is a minimal pre-numeral.

Keywords: numerals, topoi

2000 MSC: 18B25

Theory and Applications of Categories, Vol. 16, 2006, No. 19, pp 522-528.

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