Re: The set of necessary FISONs

On 31.01.2025 02:02, Richard Damon wrote:

On 1/30/25 2:28 PM, WM wrote:

But a set that has union ℕ is a set.

 But since the "Set of Necessary FISONs" isn't actually a "Set"

take the set O of v. Neumann ordinals A(n) that you claim satisfies U(A(n)) = ℕ.
 From this set O every finite subset can be subtracted without changing the result. Therefore,  by induction, no finite A(n) remains. Therefore the set O has no first ordinal. Therefore it is not a set of ordinals. Therefore your claim is wrong.
Regards, WM