Can the Universal Set be Defined as the Union of Two Sets?

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Discussion Overview

The discussion revolves around the definition of the universal set in the context of set theory, specifically whether it can be defined as the union of two sets. The scope includes theoretical considerations and implications of such a definition.

Discussion Character

  • Debate/contested

Main Points Raised

  • Kamataat questions the validity of defining the universal set as the union of two sets when proving something about them.
  • One participant asserts that it is permissible to define the universal set as the union of two sets, provided that the theory does not involve the intersection of their complements.
  • Another participant suggests that altering axioms or logic could allow for a genuine universal set.
  • A further reply raises the concern that one might also need to include the intersection of the complements of the two sets in the union to properly define the universal set.

Areas of Agreement / Disagreement

Participants express differing views on the definition of the universal set, with no consensus reached on whether it can be defined solely as the union of two sets or if additional considerations are necessary.

Contextual Notes

The discussion highlights potential limitations related to the axiomatic framework being used and the implications of including or excluding certain set operations.

Kamataat
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Let's say I have to prove something about two sets and I want to make use of the notion of the universal set. Is it OK then to define the universal set as the union of these two sets?

- Kamataat
 
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Wouldn't you also have to union (in addition to the two sets) the intersection of the complements of the two sets?
 

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