On 28 Aug 2009, at 13:47, Flammarion wrote:

> On 21 Aug, 20:49, Bruno Marchal <marc...@ulb.ac.be> wrote:
>> On 21 Aug 2009, at 09:33, Flammarion wrote:
>>  I can only hope you will work on the UDA+MGA, and understand that
>> "non-theoretical" truth have to be redefined as theoretical
>> possibilities (consistencies) observed from inside (from some first
>> person point of view).
> There is no UD.

You are meaning "no physical UD". I don't need a physical UD in the  

>>>> Thanks for quoting my sane2004 definition of comp, and showing that
>>>> indeed platonism is not part of it.
>>> "It is a version of Platonism"
>> The wording is not important.
> Maybe you could flag the wording that we are supposed
> to take serioulsy.

I have explained to you why it is preferable to avoid the term  
"Platonism" for the belief that classical logic can be applied in  
arithmetic. Even mathematicians does not call that Platonism, which  
they use for the general idea that classical logic applies to a much  
larger part of math.  Arithmetical realism is better: it is the belief  
that the truth of arithmetical sentence exists independently of any  
means (humans, theories, machines, universes, ...) to study them.

>> The point is that in the assumption of
>> CTM, (CT+ the theological act of faith),  I am using that "version of
>> platonism" only, which is just the idea that classical logic can be
>> applied to arithmetical sentences, and in the conclusion, only, we
>> have to abandon weak materialism or CTM.
> Nope. Assumptions about truth don't get you a UD which is capable of
> simulating me. You need
> a claim about existence.

You told me this before, and I did explain that I am use the truth of  
the existential statement in arithmetic, as my unique claim about  

> You argument is either based on Platonism or
> invalid

Yes, it based on Turing theorem, which with CT can be sump up by  
"universal digital machines exist".

>>>> Just arithmetical realism without which CT has no meaning at all.
>>> The CT thesis requires some mathematical
>>> claims to be true. it doesn't require numbers to actually exist
>> I have never asserted that numbers actually exist. Just that they
>> exist in the sense of the usual interpretation of existential
>> arithmetical statement are independent of me, you, or the existence  
>> or
>> not of a material world.
> There is no usual interpretation, it is disputed.

For set theoretical realism. Not for the natural numbers. I mean  
nobody, except you and ultrafinitist, doubt about the mathematical  
existence of natural numbers. They can doubt about deeper existence of  
those numbers, but I am not using this. Are you criticizing all  
theories using natural numbers (from economy to physics)?.

> Formalists don't
> think
> backeards-E has any existential implications at all

Formalist does not believe in primary matter either. And they do  
believe in formal systems, which have sense only through naïve  
arithmetic. This dodge the issue, nevertheless, because you can add  
"formal" to all existential quantifier in the reasoning without  
changing the conclusion: formal physics has to be reduced to formal  
number theory.

>> Would the two cosmic branes never have collided, and the big bang
>> never occurred, the Rieman hypothesis would still be atemporally and
>> aspatially true or false.
> Truth and falsehood don't buy you an immaterial computer simulating me
> and eveything I see.

Fortunately numbers and math are still free. If CTM is correct, you  
are emulated infinitely often in the UD*. It exists (mathematically)  
like PI and square-root of two.

>>>> Get the feeling you have change your mind on AR. You believe that a
>>>> proposition like the statement that there is no biggest prime  
>>>> number
>>>> has something to do with physics. In which physical theory you  
>>>> prove
>>>> that statement, and how?
>>> Its truth is not  a physical truth. The existence or non-existence
>>> asserted is not any kind of real existence
>> OK, in your theory "real existence" = "physical existence".
> There are two claim here:
> "real existence" = "physical existence".
> and
> "mathemaical existence" != "real existence".
> they are argued separately.

Please, define "real".

>> But if the
>> UDA is valid it would be better to write "consensual reality" =
>> "physical reality", and ontic or basic 3- existence = arithmetical
>> existence, or to abandon CTM. If UDA is non valid, it would be nice  
>> to
>> point where is the error. You said that the error is in step 0,
>> because I would have pretended something like "the number seven
>> actually exists". My answer is that I don't see where I say so. I  
>> just
>> say that the number seven exists, in the sense used by  
>> mathematicians.
>> I limit my "platonism" to arithmetic to avoid the problem of
>> "platonism" in set theory or analysis, and the CTM explains why
>> realism on natural numbers in both necessary and sufficient.
>>> I am not denying nay truths, only the interpretation of backwards-E
>>> as actual existence
>> I am using a fairly common notion of mathematical existence,
> There is no common notion, the ontology of maths is not
> a settled issue

The ontology of math is not settled, sure, but this does not prevent a  
common agreement, notably on the mathematical existence of natural  

>> and I
>> explain that once you say yes to the doctor, the notion of physical
>> existence has to be reduced to that common notion of mathematical
>> existence (actually a tiny part of arithmetical existence).
>> Up to now, the only things you criticize in the UD reasoning are
>> things *you* are introducing,
> In the sense that your Platonism is largley implict,
> and needs to be made explicit..


>> and when I remark to you that it is not
>> there, you say, it is implicit, but fail to show me where those
>> implicit statement have been used. Then you change the meaning of
>> "platonism" at every post. You define a criterium of "real" (RITSIAR)
>> without ever saying if the "I" is the third person body (which we can
>> doubt the existence) or the first person consciousness (which we
>> cannot doubt, but can't communicate).
> From the materialist POV, the difference isn't important.
>> You said that the difference is
>> epistemological, but that does not answer the question.
>> You said once that you accept mathematical truth, and then that the
>> number seven does not exist AT ALL.
> It is not some absurdity I just invented.

I was pointing that you have said successively
- the number seven exists only mathematically
- the number seven does not exist at all

Those are contradictory statements.

>> You compare mathematical object with fictional character in fairy
>> tales!
> That's another well-know position called ficitonalism
> http://plato.stanford.edu/entries/fictionalism-mathematics/

There are degrees of fictionalism.
Strong fictionalism claim that "7 is prime" is false.
Weak fictionalism still agree that "7 is prime" has most of its usual  
mathematical meaning. This is enough for the reasoning to proceed. A  
weak fictionalist can accept CT.
No mathematician are strong fictionnalist. It is an idea of  
philosopher only. I accept that the UD reasoning does not work for a  
strong fictionnalist, but this should be obvious from CT.

>> Do you really think that an arithmetician could write "Once
>> upon a time there was an odd number dreaming  becoming an even
>> number ...".
> That isn't what I wrote. What I wrote was that there are sentences
> which are a) true and b) mention the word "exists" but in which
> "exsts" is not meant to be taken literally.

When discussing fundamental science, no use of the word "exist" should  
be taken literally.

>> It would help much more if you were able to say "I don't understand
>> this or that in the reasoning, and give explicit reference to the
>> paper or posts".
> The argumetn I am actually making is that your arguemnt is either
> invalid or has an imiplict premise. How am I supposed ot
> point to an implicit premise.

By pointing on a step in the reasoning where you think I am using that  
implicit premise.



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