Description: Zero is a natural number. One of Peano's five postulates for arithmetic.
Proposition 7.30(1) of TakeutiZaring p. 42. Note: Unlike most
textbooks, our proofs of peano1 through peano5 do not use the Axiom of
Infinity. Unlike Takeuti and Zaring, they also do not use the Axiom of
Regularity. (Contributed by NM, 15-May-1994)