>>776より Thomas Jechの 証明 再録（>>667より） P48 Theorem 5.1 (Zermelo’s Well-Ordering Theorem) Every set can be well-orderd. Proof： Let A be a set. To well-order A, it suffices to construct a transfinite one-to-one sequence （aα: α < θ) that enumerates A. That we can do by induction, using a choice fiunction f for the family S of all nonempty subsets of A. We let for every α aα=f(A-{aξ：ξ<α}) if A-{aξ：ξ<α} is nonempty. Let θ be the least ordinal such that A = {αξ: ξ < θ}. Clearly,（aα：α< θ) enumerates A. ■
