On 08/03/11 14:15, 1Z wrote:

On Mar 8, 11:10 am, Andrew Soltau<andrewsol...@gmail.com>  wrote:
On 06/03/11 19:24, Bruno Marchal wrote:

On 06 Mar 2011, at 14:16, Andrew Soltau wrote:
On 07/02/11 15:22, Bruno Marchal wrote:
Comp makes precise that saying to be a machine is equivalent with
saying that there is a level of functional substitution where my
(first person) consciousness is invariant for a substitution made at
that level. Comp can show that we can never known our level of
substitution, and my reasoning works whatever I mean by my brain (it
could be the entire galaxy or the entire observable universe if
someone asks for it). CTM is vague on the level, and miss the point
that we cannot know it, if it exists.
Comp is also much more general than CTM, which relies usually on
some amount of neurophilosophy, or on representationalist theory of
the mind, and CTM is often criticized by 'externalist', like brent
Meeker for example. But comp is not annoyed by externalism, given
that it defines the (generalized) brain by the portion of universe
you need, like possibly the matrix above.
So comp is a very weak, and thus general, hypothesis. And the result
is easy to describe: physics is not the fundamental branch.
You say "And the result is easy to describe: physics is not the
fundamental branch.". This is the leap of yours I never understand.
Do you posit that a mathematical universe with no physical content
somehow automatically computes?
Computations have been discovered by mathematicians, in mathematics.
Yes but! I have no problem with the idea of a Platonic realm of
mathematical structures simply existing, with or without the physical to
instantiate them. I am aware this is a deep philosophical debate, but
the Platonic concept seems somehow more straightforward than the
physicalist concept.
Is it?
I'm not sure, I just said it seems so.
  If the Platonist supposes that there is some special mechanism
of contact between the Platonic and physical worlds that explains
mathematical knowledge, that is not straightforward. If there is no
such mechanism, then mathematical reasoning has to be explained
the way physicalists explain it, and the ontological posit of a
world is a redundant extravagance.

Surely, what Tegmark and, if I understand comp correctly, Bruno, are saying, is that this is the Platonic world, and the physical world is a process in the context of that Platonic environment. (I am lumping together the Platonic world and the arithmetical world, though there might be a distinction between them I have failed to make.)

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