Example image of eyePlorer eyePlorer map for 'Axiom of empty set': Axiom General set theory Kripke–Platek set theory Set theory Zermelo–Fraenkel set theory Existential quantification Formal language Set (mathematics) Axiom of extensionality Empty set Axiom of infinity Axiom schema of specification Formal system Axiom schema of replacement Paul Halmos Binary set Positive set theory Singleton (mathematics) Axiom of pairing Naive set theory Constructible universe Morse–Kelley set theory