Quick question about cardinals

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Discussion Overview

The discussion revolves around the definition and properties of uncountable sets of cardinal numbers, particularly in the context of ordinal numbers and equipollence. Participants explore the implications of their definitions and the nature of cardinality.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant proposes a definition of cardinal numbers based on the least ordinal number that is equipollent to a set A.
  • Another participant asserts that an uncountable set is simply an uncountable set, regardless of its relation to cardinals.
  • A participant questions how to define an uncountable set of cardinals, suggesting that under their model, all sets of cardinals "up to x" appear to be countable.
  • Another participant challenges the assertion that all cardinals are countable and suggests posting a proof, introducing the concept of uncountable ordinals and their relation to uncountable cardinals.

Areas of Agreement / Disagreement

Participants express differing views on the nature of uncountable sets of cardinals, with no consensus reached on the definitions or implications of cardinality in this context.

Contextual Notes

The discussion includes assumptions about the relationship between ordinals and cardinals, as well as the implications of countability, which remain unresolved.

Dragonfall
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Assuming we define the cardinal number for a set A as the least ordinal number b such that A and b are equipollent, how would you define an uncountable set of cardinal numbers?
 
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It's just an uncountable set. That it happens to be a set of cardinals is immaterial.
 
What I mean is that under this model every set of cardinals "up to x" seems to be countable. So how to define an uncountable one?
 
How does that imply that all cardinals are countable? Why not post a proof of that statement if it 'seems' to be so. Hint, let w be an uncountable ordinal. Such exist. It is not in bijection with any countable initial segment, so it must define an uncountable cardinal too.
 
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