Talk:Russell's paradox

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Latest comment: 22 January 2023 by CodeTalker in topic Axiom of extensionality
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"The set of all sets that do not contain themselves" listed at Redirects for discussion

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An editor has asked for a discussion to address the redirect The set of all sets that do not contain themselves. Please participate in the redirect discussion if you wish to do so. NineFiveSeven 18:25, 6 January 2020 (UTC)Reply

Can (sequence A053169 in the OEIS) be called “Russell numbers”?

Its definition is like the like the set R in the article: i.e. x belongs to R if and only if x does not belong to x (however, determine whether a positive integer x is a Russell number may be very difficult, the smallest unknown x is 319) 2402:7500:917:8A69:2C6E:A04F:8752:A7E0 (talk) 05:09, 11 July 2022 (UTC)Reply

Axiom of extensionality

The "Formal presentation" section begin with a description of the Axiom of extensionality. However I don't see how this axiom is relevant nor that it is used anywhere in the rest of the section, which just uses Comprehension, Existential instantiation and Universal instantiation. Extentionality is also not mentioned in the source cited. Should the reference to extentionality be deleted? CodeTalker (talk) 20:11, 22 January 2023 (UTC)Reply