Sujet : Re: Incompleteness of Cantor's enumeration of the rational numbers (extra-ordinary)
De : FTR (at) *nospam* nomail.afraid.org (FromTheRafters)
Groupes : sci.mathDate : 07. Jan 2025, 10:51:09
Autres entêtes
Organisation : Peripheral Visions
Message-ID : <vliteg$2554a$1@dont-email.me>
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User-Agent : MesNews/1.08.06.00-gb
It happens that WM formulated :
On 06.01.2025 22:51, FromTheRafters wrote:
WM presented the following explanation :
On 06.01.2025 19:23, FromTheRafters wrote:
WM pretended :
>
0 is a cardinal but not an ordinal.
>
Wrong.
>
Who is the zeroest clown?
Okay, maybe not with "your" definition of the ordinal numbers.
>
Ordinal numbers may be written in English with numerals and letter suffixes: 1st, 2nd or 2d, 3rd or 3d, 4th, 11th, 21st, 101st, 477th, etc [Wikipedia]
From the same source:
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https://en.wikipedia.org/wiki/Ordinal_number#Von_Neumann_definition_of_ordinalsFirst several von Neumann ordinals
0 = {} = ∅
1 = {0} = {∅}
2 = {0,1} = {∅,{∅}}
3 = {0,1,2} = {∅,{∅},{∅,{∅}}}
4 = {0,1,2,3} = {∅,{∅},{∅,{∅}},{∅,{∅},{∅,{∅}}}}
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Notice they start at zero (emptyset)
https://en.wikipedia.org/wiki/Ordinal_numeralSays:
For the mathematical concept, see Ordinal number.