Re: The set of necessary FISONs

Am 10.03.2025 um 22:04 schrieb Alan Mackenzie:

WM <wolfgang.mueckenheim@tha.de> wrote:

Z₀ is defined by induction: {} ∈ Z₀, and if {{{...{{{}}}...}}} with n
curly brackets ∈ Z₀ then {{{...{{{}}}...}}} with n+1 curly brackets ∈ Z₀.

Actually, Z₀ is NOT "defined" (WM) by that. But for Z₀ the following holds:
             {} ∈ Z₀
and
             Ax e Z₀: {x} e Z₀
            [Ax(x e Z₀ -> {x} e Z₀]
We don't "count" "curly brackets" in this context.
Hint: Mückenheim does not comprehend the difference between a mathematical object and a (some) name for that mathematical object.