Re: The set of necessary FISONs

On 28.01.2025 10:19, joes wrote:

Am Tue, 28 Jan 2025 09:58:14 +0100 schrieb WM:

On 27.01.2025 18:10, joes wrote:

Am Mon, 27 Jan 2025 15:33:01 +0100 schrieb WM:

>

Also an infinite set needs a first element.

No problem, any infinite set of FISONs has one.

But no set of FISONs the union of which is ℕ has a first element.

Yes it does. Any infinite set of FISONs has a first element.
 

But any set of FISONs fails.

If an
infinite set was existing, you could easily find a first not completely
useless element.

No, as you have shown, no element is necessary.

When every not necessary or not useful element has been discarded nothing remains.
Regards, WM