I once tried to go down this rabbit hole but gave up quickly as it's a really deep subject. Maybe start here: https://en.wikipedia.org/wiki/Set-theoretic_def

I once tried to go down this rabbit hole but gave up quickly as it's a really deep subject. Maybe start here: https://en.wikipedia.org/wiki/Set-theoretic_definition_of_natural_numbers https://en.wikipedia.org/wiki/Set-theoretic_definition_of_na...