On 17 Aug, 11:17, Bruno Marchal <marc...@ulb.ac.be> wrote:
> On 17 Aug 2009, at 11:11, 1Z wrote:
> > Without Platonism, there is no UD since it is not observable within
> > physical space. So the UDA is based on Plat., not the other way
> > round.
> Are you saying that without platonism, the square root of 2 does not
> exist?

Yes, the square root of two has no ontological existence.

> Prime number does not exist?

Yes, prime numbers have no ontological existence

>That mathematical existence is a
> meaningless notion?

Sense but no refence. Mathematical statements have
truth values but do not refere to anything outside the
formal system.

> Mathematics would be a physical illusion?

A referentless formal game, distinguished from fiction
only by its rigour and generality

> But physics use mathematics, would that not make physics illusory or
> circular?

No, because it uses mathematics empirically. The same
language that can be used to write fiction can be used to
write history. The difference is in how it used. not in the langauge

> > It's a perfectly consistent assumption. THere is no
> > disproof of materialism that doesn't beg the quesiton by
> > assuming immaterialism
> Well, I do believe in the natural numbers, and I do believe in their
> immateriality (the number seven is not made of quantum field, or
> waves, or particle).

Then you are a Platonist, and you argument is based
on Platonism.

> So either you tell me that you don't believe in the number seven, or
> that you have a theory in which the number seven is explained in
> materialist term, without assuming numbers in that theory.

The latter.

> >> This leads to major difficulties, even before approaching the
> >> consciousness problem.
> > Such as?
> Explaining number with physical notions,
> and explaining, even partially, physical notions with the use numbers.

That is just a repetition of the claim that there
are problems. You have not in the least explained  what
the problems are.

> > You arguments here are based on the idea
> > that primary matter needs to be given a
> > purely mathematical expression. That in turn
> > is based on an assumption of Platonism. If
> > Platonism is false and materialism true,
> > one would *expect* mathematical explanation
> > to run out at some point. Your "difficulty" is a
> > *prediction* of materialism , and therefore a
> > successfor materailism
> Not at all. Cf the "even partially" in my sentence just above.

That sentence does not demonstate anything
about anything.

> >> and some physicists are already open,
> >> independently of comp, to the idea that physical objects are relative
> >> mathematical (immaterial) objects. Which of course are "no material".
> >> Wheeler, Tegmark, for example.
> > They have a consisent set of assumptions. So do
> > their materialist oponents. You can't get an "is true"
> > out of a "might be true"
> Well the movie graph conclusion is that materialism is not consistent,
> unless it opt for eliminativism of persons and/or non computationalism.

Materialism=true and computationalism=false is a consistent
set of assumptions. Moreover, the movie graph doesn;t prove
what you say it does since it involves an illegitimate move from
"minimal physical basis" to "no physical basis".

> >> I tend to believe in many immaterial things. Some are absolutely real
> >> (I think) like the natural numbers.
> > There's your Platonism again. Believe what you like, but don'
> > call it proof.
> Given that the theorem is "comp => platonism", and given that I am
> open to the idea that comp could be correct, I am of course open to
> the idea that Platonism may be correct.

The theorem is platonism=>UD, UD=comp=>immaterialism

> But again, I don't need platonism (non-physicalism) to be an
> arithmetical realist, like all classical mathematicians.

Yes you do. The UD doesn't exist physically. If it doesn't
exist non-physically either, it doesn't exist, and I am not
a programme running on it.

>This is
> explicit in the assumption. The non physicalism and general
> immaterialism is a consequence of the movie graph argument. What is
> wrong with it?

The movie graph doesn;t prove
what you say it does since it involves an illegitimate move from
"minimal physical basis" to "no physical basis".

> > It changes everything. If the UD is a useful ficiton, I cannot be a
> > programme running on it, any more than I can book a flight to Narnia.
> Would you say that the 1000^1000th base ten decimal of PI is a fiction?

Yes. I don't beleive in *any* pixies, not a single one.

> >> There is a sense to say those universal machines do not exist, but it
> >> happens that they don't have the cognitive abilities to know that,
> >> and
> >> for them, in-existence does not make sense.
> > If they don't exist, they don't exist. You don't have the
> > rigourous mathematical argument you think
> > you have, you have some baroque Chuang-Tzu metaphysics.
> I do like Chuang-tzu, and I can see the relation between comp and
> Chuang-tzu, although it is more clear with Lao-Tzu, as you may see in
> "Conscience et M├ęcanisme", where an explicit correspondence is
> suggested.

> So, what you tell me is that you don't believe in *any* form of
> mathematical existence.

Not in any, and not in any pixies either.

> So you reject arithmetical realism, and thus you reject comp.

The computaitonal Theory of Mind has no implications about Platonism.

You may of course mean something else by "comp".....

> Arithmetical realism is needed to give a sense to Church thesis, which
> is part of comp.

if AR is as claim abotu the immateial existence of numbers it does
Not even remotely.

> Some posts ago, you seem to accept arithmetical realism, so I am no
> more sure of your position.

I may have assented to the *truth* of some propositions...
but truth is not existence. At least, the claim that
truth=existence is extraordinary and metaphysical...

> Bruno
> http://iridia.ulb.ac.be/~marchal/
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