On Jan 9, 12:00 pm, Bruno Marchal <marc...@ulb.ac.be> wrote:
> On 09 Jan 2012, at 14:50, Craig Weinberg wrote:
> > On Jan 9, 6:06 am, Bruno Marchal <marc...@ulb.ac.be> wrote:
> >> I agree with your general reply to Craig, but I disagree that
> >> computations are physical. That's the revisionist conception of
> >> computation, defended by Deustch, Landauer, etc. Computations have
> >> been discovered by mathematicians when trying to expalin some
> >> foundational difficulties in pure mathematics.
> > Mathematicians aren't physical? Computations are discovered through a
> > living nervous system, one that has been highly developed and
> > conditioned specifically for that purpose.
> Computation and mechanism have been discovered by many people since
> humans are there. It is related to the understanding of the difference
> between "finite" and "infinite". The modern notion has been discovered
> independently by many mathematicians, notably Emil Post, Alan Turing,
> Alonzo Church, Andrzei Markov, etc.
> With the comp. hyp., this is easily explainable, given that we are
> somehow "made of" (in some not completely Aristotelian sense to be
> sure) computations.

They are making those discoveries by using their physical brain

> >> We can implement
> >> computation in the physical worlds, but that means only that the
> >> physical reality is (at least) Turing universal. Theoretical computer
> >> science is a branch of pure mathematics, even completely embeddable
> >> in
> >> arithmetical truth.
> > And pure mathematics is a branch of anthropology.
> I thought you already agreed that the arithmetical truth are
> independent of the existence of humans, from old posts you write.
> Explain me, please, how the truth or falsity of the Riemann
> hypothesis, or of Goldbach conjecture depend(s) on anthropology.
> Please, explain me how the convergence or divergence of phi_(j)
> depends on the existence of humans (with phi_i = the ith computable
> function in an enumeration based on some universal system).

The whole idea of truth or falsity in the first place depends on
humans capacities to interpret experiences in those terms. We can read
this quality of truth or falsity into many aspects of our direct and
indirect experience, but that doesn't mean that the quality itself is
external to us. If you look at a starfish, you can see it has five
arms, but the starfish doesn't necessarily know it had five arms.

What about arabic numerals? Seeing how popular their spread has been
on Earth after humans, shouldn't we ask why those numerals, given an
arithmetic universal primitive, are not present in nature
independently of literate humans? If indeed all qualia, feeling,
color, sounds, etc are a consequence of arithmetic, why not the
numerals themselves? Why should they be limited to human minds and


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