Sewing Machine’s previous comment isn’t really a definition, but it leads to the following:
“n is a finite ordinal if and only if for all properties P such that P(0) and P(k) implies P(k+1), we have P(n).”
In other words, the finite numbers are “the smallest” collection of objects containing 0 and closed under successorship.
(If “properties” means predicates then our definition uses second-order logic. Or it may mean ‘sets’ in which case we’re using set theory.)
Sewing Machine’s previous comment isn’t really a definition, but it leads to the following:
“n is a finite ordinal if and only if for all properties P such that P(0) and P(k) implies P(k+1), we have P(n).”
In other words, the finite numbers are “the smallest” collection of objects containing 0 and closed under successorship.
(If “properties” means predicates then our definition uses second-order logic. Or it may mean ‘sets’ in which case we’re using set theory.)