Description: Define the class of
natural numbers as the smallest inductive set, which
is valid provided we assume the Axiom of Infinity. Definition 6.3 of
[Eisenberg] p. 82.
Note: the natural numbers are a subset of the ordinal numbers
df-on 4228. Later, when we define complex numbers, we
will be able to
also define a subset of the complex numbers with analogous properties
and operations, but they will be different sets. (Contributed by NM,
6-Aug-1994.) Use its alias dfom3 4444 instead for naming consistency with
set.mm. (New usage is discouraged.) |