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From: Alan Mackenzie <acm@muc.de>
Newsgroups: sci.math
Subject: Re: The non-existence of "dark numbers"
Date: Thu, 13 Mar 2025 12:59:02 -0000 (UTC)
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WM <wolfgang.mueckenheim@tha.de> wrote:
> On 12.03.2025 22:31, Alan Mackenzie wrote:
>> WM <wolfgang.mueckenheim@tha.de> wrote:
>>> On 12.03.2025 18:42, Alan Mackenzie wrote:
>>>> WM <wolfgang.mueckenheim@tha.de> wrote:

[ .... ]

>>>>> Learn what potential infinity is.

>>>> I know what it is.  It's an outmoded notion of infinity, popular in =
the
>>>> 1880s, but which is entirely unneeded in modern mathematics.

>>> That makes "modern mathematics" worthless.

>> What do you know about modern mathematics?

> I know that it is self-contradictory because it cannot distinguish=20
> potential and actual infinity.

It can, but doesn't need to.  Potential and actual infinity are needless
concepts which only serve to confuse and obfuscate.  If you disagree,
feel free to cite a standard result in standard mathematics which depends
on these notions.

> When |=E2=84=95| \ |{1, 2, 3, ..., n}| =3D =E2=84=B5o, ....

Do you ever bother to check what you write?  The difference operator \
applies to sets, not to cardinal numbers.  I can guess what you mean, but
your readers shouldn't have to guess that.

> .... then |=E2=84=95| \ |{1, 2, 3, ..., n+1}| =3D =E2=84=B5o. This hold=
s for all elements
> of the inductive set, i.e., all FISONs F(n) or numbers n which have
> more successors than predecessors.

I.e. all natural numbers.

> Only those contribute to the inductive set!

The inductive set is all natural numbers.  Why must you make such a song
and dance about it?

> Modern mathematics must claim that contrary to the definition =E2=84=B5=
o
> vanishes to 0 because =E2=84=95 \ {1, 2, 3, ...} =3D { }.  That is blat=
antly
> wrong and shows that modern mathematicians believe in miracles.
> Matheology.

Modern mathematics need not and does not claim such a ridiculous thing.
Your understanding of it is what's lacking.

>> You may recall me challenging others in another recent thread to cite
>> some mathematical result where the notion of potential/actual infinity
>> made a difference.  There came no coherent reply (just one from Ross
>> Finlayson I couldn't make head nor tail of).  Potential infinity isn't
>> helpful and isn't needed anymore.

>>>>>> 3. The least element of the set of dark numbers, by its very
>>>>>>       definition, has been "named", "addressed", "defined", and
>>>>>>       "instantiated".

> It is named but has no FISON. That is the crucial condition.

What the heck does it mean for a number to "have" a FISON?  Assuming you
can define that, you need to prove that the least "dark number" "has" no
FISON.  And assuming you can do that (which I very much doubt), you then
have to clarify what that condition is crucial to and how.

>>>> So you counter my proof by silently snipping elements 4, 5 and 6 of =
it?
>>>> That's not a nice thing to do.

>>> They were based on the mistaken 3 and therefore useless.

>> You didn't point out any mistake in 3.  I doubt you can.

> I told you that potential infinity has no last element, therefore there=
=20
> is no first dark number.

The second part of your sentence does not follow clearly from the first,
therefore the sentence is false.  And even if it were not false, it has
no bearing on my item 3.

But I can agree with you that there is no first "dark number".  That is
what I have proven.  There is a theorem that every non-empty subset of
the natural numbers has a least member.  On the assumption (yours) that
"dark numbers" are a subset of the natural numbers, that proves that
there are no "dark numbers" at all.

>>>>> Try to remove all numbers individually from the harmonic series suc=
h
>>>>> that none remains. If you can't, find the first one which resists.

>>>> Why should I want to do that?

>>> In order to experience that dark numbers exist and can't be manipulat=
ed.

>> Dark numbers don't exist, as Jim and I have proven.

> When |=E2=84=95| \ |{1, 2, 3, ..., n}| =3D =E2=84=B5o, then |=E2=84=95|=
 \ |{1, 2, 3, ..., n+1}| =3D=20
> =E2=84=B5o. How do the =E2=84=B5o dark numbers get visible?

There is no such thing as a "dark number".  It's a figment of your
imagination and faulty intuition.

>>> Induction cannot cover all natural numbers but only less than remain
>>> uncovered.

>> The second part of that sentence is gibberish.  Nobody has been talkin=
g
>> about "uncovering" numbers, whatever that might mean.  Induction
>> encompasses all natural numbers.  Anything it doesn't cover is not a
>> natural number, by definition.

> Every defined number leaves =E2=84=B5o undefined numbers. Try to find a=
=20
> counterexample. Fail.

What the heck are you talking about?  What does it even mean for a number
to "leave" a set of numbers?  Quite aside from the fact that there is no
mathematical definition of a "defined" number.  The "definition" you gave
a few posts back was sociological (talking about how people interacted
with eachother) not mathematical.

> Regards, WM

--=20
Alan Mackenzie (Nuremberg, Germany).