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From: Ben Bacarisse <ben@bsb.me.uk>
Newsgroups: sci.math
Subject: Re: Incompleteness of Cantor's enumeration of the rational numbers (extra-ordinary)
Date: Tue, 03 Dec 2024 11:35:38 +0000
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"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> writes:

> On 12/2/2024 4:00 PM, Chris M. Thomasson wrote:
>> On 12/2/2024 3:59 PM, Moebius wrote:
>>> Am 03.12.2024 um 00:58 schrieb Chris M. Thomasson:
>>>> On 12/2/2024 3:56 PM, Moebius wrote:
>>>>> Am 03.12.2024 um 00:51 schrieb Chris M. Thomasson:
>>>>>> On 12/1/2024 9:50 PM, Moebius wrote:
>>>>>>> Am 02.12.2024 um 00:11 schrieb Chris M. Thomasson:
>>>>>>>> On 11/30/2024 3:12 AM, WM wrote:
>>>>>>>
>>>>>>>>> Finite initial segment[s]: F(n) = {1, 2, 3, ..., n}    (n e IN).
>>>>>> [...]
>>>>>>
>>>>>> When WM writes:
>>>>>>
>>>>>> {1, 2, 3, ..., n}
>>>>>>
>>>>>> I think he might mean that n is somehow a largest natural number?
>>>>>
>>>>> Nope, he just means some n e IN.
>>>>
>>>> So if n = 5, the FISON is:
>>>>
>>>> { 1, 2, 3, 4, 5 }
>>>>
>>>> n = 3
>>>>
>>>> { 1, 2, 3 }
>>>>
>>>> Right?
>>>
>>> Right.
>> Thank you Moebius. :^)
>
> So, i n = all_of_the_naturals, then

You are in danger of falling into one of WM's traps here.  Above, you
had n = 3 and n = 5.  3 and 5 are naturals.  Switching to n =
all_of_the_naturals is something else.  It's not wrong because there are
models of the naturals in which they are all sets, but it's open to
confusing interpretations and being unclear about definition is the key
to WM's endless posts.

> { 1, 2, 3, ... }
>
> Aka, there is no largest natural number and they are not limited. Aka, no
> limit?

The sequence of FISONs has a limit.  Indeed that's one way to define N
as the least upper bound of the sequence

 {1}, {1, 2}, {1, 2, 3}, ...

although the all terms involved need to be carefully defined.

> Right?

The numerical sequence 1, 2, 3, ... has no conventional numerical limit,
but, again, if the symbols 1, 2, 3 etc stand for sets (as in, say, Von
Neumann's model for the naturals) then the set sequence

 1, 2, 3, ...

does have a set-theoretical limit: N.

-- 
Ben.