From: Marc Geddes (marc_geddes@yahoo.co.nz)
Date: Wed Oct 06 2004 - 23:25:02 MDT
--- Robin Lee Powell <rlpowell@digitalkingdom.org>
wrote:
> At http://yudkowsky.net/bookshelf.html#k_rp we have:
>
> Penrose isn't trying to explain quantum physics;
> he's trying to
> persuade you that the human mind isn't
> Turing-computable.
> (Penrose is right about this, although purely by
> coincidence.)
>
> But at
>
http://yudkowsky.net/tmol-faq/miscellaneous.html#turing
> we
> have that human thought, at least, *is* turing
> computable.
>
> I'm not certain that this is a contradiciton, but
> I'd like to see
> more about Eliezer's views on this point; anybody
> got a link?
>
> -Robin
>
> --
> http://www.digitalkingdom.org/~rlpowell/ ***
> http://www.lojban.org/
> Reason #237 To Learn Lojban: "Homonyms: Their
> Grate!"
>
I read Penroses's books several times but never
believed the guy. It was clear to me even then that
he was hopelessly confused. Penrose is confused about
Godel's theorem and he's confused about levels of
explanation.
For starters, as I pointed out on SL4 not so long ago,
'undecidability' and 'uncomputability' simply refer to
classes of problem of infinite complexity. As far as
we know, there is nothing undecidable or uncomputable
about any *finite* part of the physical world. Whilst
there are theories that some finite part of physical
reality could be uncomputable, this is quite unproven.
Further, Godel's Theorem is referring to axiomatic
reasoning and conclusions that are 100% certain. But
if we drop the requirement that computers have to
derive certain conclusions, then there is nothing
stopping computers from deriving probabilistic
conclusions about any of the so-called 'uncomputable'
functions. Godel's Theorem simply means that even in
maths we can't form conclusions that are 100% certain.
It definitely *doesn't say* that there are any
absolutely undecidable maths truths.
Finally reductionism/holistic again. Penrose keeps
making the reductionist mistake of thinking that high
level concepts somehow have to have explanations in
terms of fundamental physics.
For instance he is mystified by the 'flow of time' and
thinks that the laws of physics have to be changed to
explain it, whereas in fact 'the flow of time' is a
high-level concept emerging from the way humans view
the world. Time does not exist at the physics level.
Similarly with consciousness - he is mystified and
thinks that the explanation has to be somehow
'written' into the fundamental laws of physics.
Extreme reductionist error.
And so on.
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