Remark 3.4.12 The axioms of set theory that we have introduced (Axiom 3.1-3.11, excluding the dangerous Axiom 3.8) are known as the Zermelo-Fraenkel axioms of the theory, after Ernest Zermelo (1871-1953) and Abraham Fraenkel (1891-1965). There is one further axiom we will eventually need, the famous axiom of choice (see Section 8.4), giving rise to the Zermelo-Fraenkel-Choice (ZFC) axioms of set theory, but we will not need this axiom for some time.