delayed reply

From: Juergen Schmidhuber <>
Date: Thu, 25 Feb 1999 15:02:11 +0100

A somewhat delayed reply to certain previous posts. I apologize
if there is some redundancy with subsequent messages by others.

Gilles Henri writes:

> I have much more objections in fact to models like Schmidhuber's one:
> again what are these Turing machines, Big programmer and so on made of?

This does not seem essential and is therefore left unspecified. You can
try to make one of the stuff you find in your own universe. Note that
many of the Great Programmer's universes indeed feature another Great
Programmer who programs another (possibly different) Big Computer to
run all possible universes. Obviously there are infinite chains of
Great Programmers.

> Who is "interpreting" a string as a Universe?

This may be a somewhat misleading question. It seems based on the
assumption that the interpreter is not himself part of a computable
world representable by bitstrings. E.g., your internal state changes
and email messages and worries about "interpretations" are just part of
the computable evolution of a particular universe. It does not matter
that we may produce computable outputs claiming otherwise ("it doesn't
feel like it"), to be interpreted by other computable interpreters like
ourselves. None of us needs to be aware of the bitstring representation.

> Is it true that in this model every "state" is finite, that is the set of
> all possible states of all possible universes is countable?

Yes, definitely! Just like sqrt(2) is describable by a finite
algorithm. Most real numbers, however, are not describable at all -
they convey infinite information. We cannot even talk about them. No
room for them in any of the Great Programmer's universes!

> Does it mean for example that the possible values of physical
> constants are discrete?

Discrete or at least computable. In none of the Great Programmer's
universes there is Super-Turing computability, although the concept
has become fashionable in our particular computable universe, and lots
of computable people make computable noises about it.

>The simplest program just enumerates all integer
>numbers. If you can tell me which integer describes the existence of
>consciousness or to the existence of anything like an electron or whatever
>you want, I would be very grateful to you!

To comment on this in the spirit above, I took a paragraph from my little
paper and replaced every occurrence of "life" by "consciousness":

What is consciousness? The answer depends on the observer. For instance,
certain substrings of E_k may be interpretable as the evolving
consciousness of a living thing L_k in U_k. Different observers will
have different views though. What's consciousness to one observer will
be noise to another. In particular, if the observer is not like the
Great Programmer but also inhabits U_k, then its own consciousness may
be representable by a similar substring. Assuming that recognition
implies relating observations to previous knowledge, both L_k's and
the observer's consciousness will have to share mutual algorithmic
information: there will be a comparatively short algorithm computing
L_k's from the observer's consciousness, and vice versa.

And Bruno wrote:

> ...I will be very short. Nevertheless, about Schmidhuber, although there
> is some superficial resemblance with my thesis, I realise Schmidhuber has
> an inconsistant understanding of the computationnalist hypothesis. More
> on this latter....

Did I miss a follow-up message? I guess I haven't seen any subsequent
explanation of Bruno's claim.

The Great Programmer religion is a religion of simplicity. One may
believe in it until (a) there is evidence against it (e.g., someone shows
that our own universe won't run without all the real numbers), or (b) someone
comes up with an even simpler explanation of everything. Right now neither
option seems very likely to me. ;^)

Juergen Schmidhuber
Received on Thu Feb 25 1999 - 06:29:52 PST

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