Example image of eyePlorer eyePlorer map for 'Axiom of extensionality': Axiom Computer science Logic Mathematics Set theory Zermelo–Fraenkel set theory Equality (mathematics) Formal language If and only if Set (mathematics) Universal quantification Predicate logic Urelement Type theory Empty set Axiom of regularity Extensionality Paul Halmos Axiom of power set Axiom of union Mostowski collapse lemma Axiom of empty set Axiom of pairing Code (set theory) Positive set theory Zermelo set theory Ackermann set theory Constructive set theory General set theory Kripke–Platek set theory Axiom schema of specification Diaconescu's theorem Kripke–Platek set theory with urelements New Foundations Non-well-founded set theory Quasi-set theory Extension (semantics) Morse–Kelley set theory Axiom of infinity Nigger in the woodpile Extension (mathematics) Naive set theory Von Neumann–Bernays–Gödel set theory Constructible universe Mereotopology Scott–Potter set theory Mereology Willard Van Orman Quine First-order logic