On 19 Aug, 15:16, Bruno Marchal <marc...@ulb.ac.be> wrote:
> On 19 Aug 2009, at 10:33, Flammarion wrote:
> > On 19 Aug, 08:49, Bruno Marchal <marc...@ulb.ac.be> wrote:
> >> On 19 Aug 2009, at 02:31, Brent Meeker wrote:
> >>> Bruno Marchal wrote:
> >>>> This is not the point. The point is that if you develop a correct
> >>>> argumentation that you are material, and that what we "see"  
> >>>> around us
> >>>> is material, then the arithmetical P. Jone(s) will also find a
> >>>> correct
> >>>> argumentation that *they* are material, and that what they see is
> >>>> material. The problem is that if you are correct in "our physical
> >>>> reality" their reasoning will be correct too, and false of course.
> >>>> But
> >>>> then your reasoning has to be false too.
> >>>> The only way to prevent this consists in saying that you are not
> >>>> Turing-emulable,
> >>> Why can't I just say I'm not Turing emulated?  It seems that your
> >>> argument uses MGA to
> >>> conclude that no physical instantaion is needed so Turing-
> >>> emulable=Turing-emulated.  It
> >>> seems that all you can conclude is one cannot *know* that they have
> >>> a correct argument
> >>> showing they are material.  But this is already well known from
> >>> "brain in a vat" thought
> >>> experiments.
> >> OK. But this seems to me enough to render invalid any reasoning
> >> leading to our primitive materiality.
> >> If a reasoning is valid, it has to be valid independently of being
> >> published or not, written with ink or carbon, being in or outside the
> >> UD*. I did not use MGA here.
> > That is false. You are tacitly assuming that PM has to be argued
> > with the full force of necessity --
> I don't remember. I don't find trace of what makes you think so. Where?

Well, if it;s tacit you wouldn't find  a trace.

Other than that. all pointing out that I might be in a UDA
and therefore wrong doesn't mean I am wrong now. only
that I am not necessarily right.

If you don't think the UDA is meant to show that
I am not necessarily right, maybe you could say what
it is meant to show

> > although your own argument does
> > not have that force.
> If there is a weakness somewhere, tell us where.

The conclusion of your argument *is* a necessary truth?

> > In fact, PM only has to be shown to be more
> > plausible than the alternatives. It is not necessarily true because of
> > sceptical hypotheses like the BIV and the UD, but since neither of
> > them has much prima-facie plausibility, the plausibility og PM
> > is not impacted much
> ?  Ex(x = UD) is a theorem of elementary arithmetic.

backwards-E x=UD is indeed true. Schools should not
be teaching that backwards-E means ontological existence,
since that is an open question among philosophers.

> I have been taught elementary arithmetic in school, and I don't think  
> such a theory has been refuted since.
> You will tell me that mathematical existence = non existence at all.  
> You are the first human who says so.

I am not the first formalist.
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