Changes

However, in some non-standard model of [[Peano Arithmetic]], ∞ is treated as an actual number.

However, in some non-standard model of [[Peano Arithmetic]], ∞ is treated as an actual number.

In [[Zermelo-Fraenkel]] set theory, one must assert that an infinite set exists. This is known as the [[Axiom of Infinity]].

In [[Zermelo-Fraenkel]] set theory, one must assert that an infinite set exists. This is known as the [[Axiom of Infinity]].  Some constructive mathematicians and practicians of elementary techniques work without this axiom, and determine which results may be proved without assuming it.  

[[Category:Mathematics]]

[[Category:Mathematics]]