# A Russell-like paradox

**URL:** <https://boards.straightdope.com/t/a-russell-like-paradox/124032>\
**Category:** Factual Questions\
**Created:** [August 15, 2002, 3:47pm UTC](https://boards.straightdope.com/t/a-russell-like-paradox/124032 "2002-08-15T15:47:57Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\
**Post date:** [August 15, 2002, 8:06pm UTC](https://boards.straightdope.com/t/a-russell-like-paradox/124032/21 "2002-08-15T20:06:43Z")

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Note that most people are taught about the idea of a “universal set” that contains everything.

This Is A Bad Idea.

The farther away from a “universal set” you get, the happier you’ll be.

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**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\
**Post date:** [August 15, 2002, 8:35pm UTC](https://boards.straightdope.com/t/a-russell-like-paradox/124032/22 "2002-08-15T20:35:04Z")

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**Jabba** ’s proof of why we cannot have a sets x and y each containing the other is valid, but not satisfying. What you have shown is that the existence of x and y is not allowed by the Axiom of Regularity, not how the existence of x and y (in the absence of AoR) would create a Russell-like paradox.

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**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\
**Post date:** [August 15, 2002, 8:58pm UTC](https://boards.straightdope.com/t/a-russell-like-paradox/124032/23 "2002-08-15T20:58:03Z")

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> [@](#):
>
> \*Originally posted by ftg \*  
> \*\*Note that most people are taught about the idea of a “universal set” that contains everything.
> 
> This Is A Bad Idea.
> 
> The farther away from a “universal set” you get, the happier you’ll be. \*\*

I’m kinda ambivalent on this issue. For the non-mathematician, it really doesn’t matter that much. But yeah, once you get into any sort of advanced math, you need to do away with it.

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