On 1/18/2021 2:52 PM, WM wrote:
> Jim Burns schrieb
> am Montag, 18. Januar 2021 um 19:14:53 UTC+1:
>> On 1/17/2021 4:58 PM, WM wrote:
>>> Jim Burns schrieb
>>> am Sonntag, 17. Januar 2021 um 21:18:22 UTC+1:
>>>> Mathematics is the language of physics.
>>>
>>> Set theory is not the language of physics.
>>
>> Bullshit.
>> What _you_ (WM) mean by "set theory" is _precisely_
>> the language of physics.
>
> Really? It depends on the choice of labels,
> what result is occuring?
First order logic, which you don't know is labelled first order
logic, is what physics uses to reason about the unobserved-so-far
portion of our universe (this is called prediction), whatever
label you attach to it.
>> Physics is in the business of reasoning about _what we_
>> _have not seen_ Does the conservation of energy also hold
>> in the core of the Sun? Physics says "Yes, even though we
>> have not seen the core of the Sun."
>
> Scrooge McDuck daily receives 1000000000000000 $ and
> issues only 1 $. Set theory yields the limit: bankrupt.
> BUT ONLY IF HE ISSUES THE OLDEST DOLLARS. Otherwise he
> will not get bankrupt.
Each natural number can be matched with each multiple
of 1e15. This is why we say the infinitely many McDuck dollars
taken one at a time is precisely as many as the infinitely
many McDuck dollars taken 1e15 at a time.
You (WM) would like this to be complicated, but it's not.
Take the decimal numeral for a natrual number. Append
fifteen 0's to its right end. You have the numeral for
one and only one multiple of 1e15.
Take the decimal numeral for a multiple of 1e15. Remove
the fifteen 0'sfrom its right end. you have one and only
one numeral for a natural.
Match.
This is not how finite sets behave, but the set of naturals
is not finite.
> Can really any intelligent person recommend this
> matheologial nonsense for physics?
If we want to describe an (indefinite) thing in 0,1,2,3,4,...
then it is followed immediately by another thing and,
except for 0, it is preceded immediately by another thing.
Each thing in 0,1,2,3,4,... matches to a corresponding thing
in 1,2,3,4,5,... which is a proper subset of 0,1,2,3,4,...
This is what your Scrooge McDuck story comes down to,
matching with a proper subset.
Whether intelligent person should recommend using something
like 0,1,2,3,4,... to describe some physics depends upon
what's being described. If it's an infinite sequence that
needs to be described, then an intelligent person should
recommend something that can be matched with a proper subset.
Because that's what it is.
Your intuition disagrees with truth-preserving inferences
here. Truth-preserving inferences are more reliable.
>> You (WM) oppose this. You demand that we _see_ numbers if
>> we are to reason about them.
>
> The interior of the sun exists whether we see it or not.
Does it exist? How do you know? Have you seen it?
The interior of the Sun is a theoretical construct.
Very close to *all* of what we *think* the universe is
has never been observed by us and will never be observed
by us. The line you want to draw is not where you think it is.
My point is, though, that _we do not see_ the interior of
the Sun. *Nonetheless* we reason about it. Our logic works
just fine on the unseen
> A number sa an abstraction of reality does not exist
> if no-one abstracts it.
> You should try to understand this big difference.
It is a difference that makes no difference.
Numbers exist in the same sense (or do not exist,the same)
before and after they are "abstracted".
We describe a thing -- maybe a natural number is have
a finite linear sequence of predecessors --
We reason from the description to new statements.
The new statements are true of everything described.
Being "abstracted" plays no part.
>> What you oppose, what you call
>> "set theory" (really, first order logic) is _precisely_ what
>> physics uses to speak of the conservation of energy
>> _everywhere_ seen, unseen, never yet seen, or never to be seen.
>
> That is nonsense.
> Physics uses *logic* for its deductions but
> no first- or second-order logic. That is simply rubbish.
?
Maybe someone sometime mentioned to you that
*physics uses variables*
If you don't believe me, ask your colleagues.
PLEASE do that, and tell us how they react.
Don't overlook reminding your colleagues of your academic
freedom to lecture on things you're ignorant of.
>> Here is the part of your proof you consider unnecessary
>> to write out:
>> | Cherry-pick results that seem to suggest the pre-selected
>> | result. Ignore the rest.
>
> I don't. Let P denote the set of prime numbers,
> then |N ∩ [0, n]| / |P∩ [0, n]| decreases below
> every positive eps. That means
> Lim_{n--> oo} |N ∩ [0, n]| / |P ∩ [0, n]| = 0.
> It does not mean that there are no prime numbers.
Neither does the other mean that there are twice as many
naturals as evens.