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  2. Set theory - Wikipedia

    en.wikipedia.org/wiki/Set_theory

    Set theory is the branch of mathematical logic that studies sets, which can be informally described as collections of objects. Although objects of any kind can be collected into a set, set theory — as a branch of mathematics — is mostly concerned with those that are relevant to mathematics as a whole. The modern study of set theory was ...

  3. Zermelo–Fraenkel set theory - Wikipedia

    en.wikipedia.org/wiki/Zermelo–Fraenkel_set_theory

    In set theory, Zermelo–Fraenkel set theory, named after mathematicians Ernst Zermelo and Abraham Fraenkel, is an axiomatic system that was proposed in the early twentieth century in order to formulate a theory of sets free of paradoxes such as Russell's paradox. Today, Zermelo–Fraenkel set theory, with the historically controversial axiom ...

  4. Martin's axiom - Wikipedia

    en.wikipedia.org/wiki/Martin's_axiom

    In the mathematical field of set theory, Martin's axiom, introduced by Donald A. Martin and Robert M. Solovay, [1] is a statement that is independent of the usual axioms of ZFC set theory. It is implied by the continuum hypothesis, but it is consistent with ZFC and the negation of the continuum hypothesis. Informally, it says that all cardinals ...

  5. Kripke–Platek set theory - Wikipedia

    en.wikipedia.org/wiki/Kripke–Platek_set_theory

    If any set is postulated to exist, such as in the axiom of infinity, then the axiom of empty set is redundant because it is equal to the subset {}.Furthermore, the existence of a member in the universe of discourse, i.e., ∃x(x=x), is implied in certain formulations [1] of first-order logic, in which case the axiom of empty set follows from the axiom of Δ 0-separation, and is thus redundant.

  6. Von Neumann–Bernays–Gödel set theory - Wikipedia

    en.wikipedia.org/wiki/Von_Neumann–Bernays...

    Von Neumann–Bernays–Gödel set theory. In the foundations of mathematics, von Neumann–Bernays–Gödel set theory (NBG) is an axiomatic set theory that is a conservative extension of Zermelo–Fraenkel–choice set theory (ZFC). NBG introduces the notion of class, which is a collection of sets defined by a formula whose quantifiers range ...

  7. List of axioms - Wikipedia

    en.wikipedia.org/wiki/List_of_axioms

    Together with the axiom of choice (see below), these are the de facto standard axioms for contemporary mathematics or set theory. They can be easily adapted to analogous theories, such as mereology. Axiom of extensionality; Axiom of empty set; Axiom of pairing; Axiom of union; Axiom of infinity; Axiom schema of replacement; Axiom of power set ...

  8. Russell's paradox - Wikipedia

    en.wikipedia.org/wiki/Russell's_paradox

    t. e. In mathematical logic, Russell's paradox (also known as Russell's antinomy) is a set-theoretic paradox published by the British philosopher and mathematician Bertrand Russell in 1901. [1][2] Russell's paradox shows that every set theory that contains an unrestricted comprehension principle leads to contradictions. [3]

  9. Axiom schema of specification - Wikipedia

    en.wikipedia.org/wiki/Axiom_schema_of_specification

    In many popular versions of axiomatic set theory, the axiom schema of specification, [ 1 ] also known as the axiom schema of separation (Aussonderungsaxiom), [ 2 ]subset axiom[ 3 ], axiom of class construction, [ 4 ] or axiom schema of restricted comprehension is an axiom schema. Essentially, it says that any definable subclass of a set is a set.