User blog comment:Syst3ms/YAUD/@comment-30754445-20180810132619/@comment-30754445-20180811200001

@Alemagno12

"ψM(x) isn't given an explicit value though, so it's not an OCF"

Is there something you can do with ordinals, that you cannot do with ψM(x)?

More specifically:

Does ψ(ψM(x)+1) represent an ordinal?

Does ψ(ψM(x)*2) represent an ordinal?

Does ψ(ψM(x)^2) represent an ordinal?

Does ψ(ψM(x)^ψM(x)) represent an ordinal?

If the answer to all the above is "yes", then for all practical purposes ψM(x) is an ordinal.