Re: Questions on Russell's "Why Occam" paper

From: Patrick Leahy <jpl.domain.name.hidden>
Date: Mon, 6 Jun 2005 12:06:06 +0100 (BST)

On Mon, 6 Jun 2005, Russell Standish wrote:

> I am beginning to regret calling the all descriptions ensemble with
> uniform measure a Schmidhuber ensemble. I think what I meant was that
> it could be generated by a standard dovetailer algorithm, running for
> 2^\aleph_0 timesteps.

It can't! Timesteps are denumerable, hence this statement is just a
contradiction in terms. You better postulate your ensemble without
reference to any algorithm to generate it.

> However, as the cardinality of "my" ensemble is actually "c"
> (cardinality of the real numbers), it is quite probably a completely
> different beast.

There you go again with your radical compression. Without the reading I've
been doing in the last two weeks, I wouldn't have been able to decode this
statement as meaning:

2^\aleph_0 = \aleph_1 (by definition)

To assume c = \aleph_1 is the Continuum Hypothesis, which is unprovable
(within standard arithmetic).

<snip>
>
> Now an observer will expect to find a SAS in one of the descriptions
> as a corrolory of the anthropic principle, which is explicitly stated
> as one of the assumptions in this work. I make no bones about this - I
> consider the anthropic principle a mystery, not self-evident like
> many people.

Very few supporters of the AP would "expect to find a SAS" in a bitstring.
Until you *specify* a way of interpreting the string, it contains nothing
but bits.

> Why should an observer expect to see a token of erself
> embedded in reality? That is the mystery of the AP.

What ARE you talking about? Observer's don't see tokens of themselves...
if anyone (God?) has a 3rd-person/bird's eye view, it is certainly not
someone who is included in any particular reality. No way is anything like
this implied by the AP. All the AP requires is that there *be*
observers/SAS in (real) universes, which is true in our case at least.

>
>> And now we find not only that the bit string is
>> a description, but it is a complex enough description to describe SAS's?
>> How does that work?
>>
>
> The bitstrings are infinite in length. By reading enough bits, they can
> have arbitrarily complex meanings attached to them.
>

In particular, any bitstring can be "interpreted" as any other bitstring
by an appropriate map. Hence until you specify an interpreter you are
simply not proposing a theory at all.

<snip>
>
> All that is discussed in this paper is appearances - we only try to
> explain the phenomenon (things as they appear). No attempt is made to
> explain the noumenon (things as they are), nor do we need to assume
> that there is a noumenon.

Most readers of your paper would take it that you are making a strong
ontological proposition, i.e. that the basis of reality is your set of
bitstrings. If this is *not* the case, and you think the bitstrings may be
represented in some deeper reality (or maybe are just metaphors), then
what is the motivation for your proposal? Why do we need to think about
this intermediate layer of bitstrings? The original simplicity goes out
the window.

BTW I'm with Kant: you can't have an appearance without an underlying
reality, even if that is unknowable.

> Bruno Marchal has a detailed discussion on this in his thesis, and
> concludes that he "has no need for this hypothesis" (what he calls the
> extravagant hypothesis).
>
> So the former statement is true :[the description strings are] things
> that "observer" TM's observe and map to integers. It is also true that
> descriptions of self aware observers will appear within the description
> by the Anthropic Principle. The phenomenon of observerhood is included.
> However where the observers actually live is not a meaningful question
> in this framework.

I think either your terminology or you model has now got very confused.
Are your "observer" TMs the observers (SAS) whose experiences your theory
is trying to explain? In this case "where they live" is crucial because it
defines the environment the SAS find themselves in. If you are not
careful your theory becomes effectively that we are all "brains in
bottles" or Leibnizian monads, which is solipsism by another name. Or are
your "observers" the missing "interpreters" in your theory which give it
meaning, and allow us to find (in principle) the SAS within the bitstrings
that represent actual observers like us? In this case it's unhelpful to
call these meta-entities "observers"; rather, in effect, they constitute
the (meta-)laws of physics. Incidentally, a TM by itself can't generate
meaning, as it is only a map from integers to integers. You still have to
specify externally how to interpret the code as something more than a mere
number. (E.g. in the Turing test the output bits have to be processed into
English language text).

<snip>

>> The page then goes on to make some comments about measure applied to
>> universes. Here again I am confused about how to relate it to all that
>> has been descibed. What are the analogs of universes, in this model?
>> Is it "descriptions", the infinite bit strings? From what has been
>> presented so far, I don't understand how to relate our experience of
>> reality to this model.
>>
>
> Each description is a possible universe, composed of an infinite
> amount of information. Any observer will of course only comprehend a
> finite amount information, and hence be in a superposition of a subset
> of universes corresponding to that finite information. Admittedly the
> usage of the term "universe" is slightly strange here.

Not to mention the terms "observer" and "superposition". In QM, which is
the natural context, superposition implies that it is possible sometimes
to observe (and predict) interference effects. I don't see how this can
happen in your sense, since there is no interaction between descriptions.

> Alterantively, one could talk about "observer moments" as corresponding
> to the equivalence classes of descriptions. This interpretation would be
> more natural to many here on this list.

Surely not equivalence classes of *descriptions*? If a description =
universe, some will contain many different observers and hence OMs.

>
> In section 3 of the paper, I now introduce a temporal dimension, with
> the observer repeatedly sampling the set of all descriptions, with the
> proviso that successor states can only differ by a finite number of bits.
>

So are you saying that your "descriptions/universes" in Section 2 don't
contain a representation of time? why shouldn't they? If they don't, how
can they represent "universes" in any sense at all? If they do, what's the
point of introducing a second, independent "time dimension" in your
meta-world of "observer" processing "universes"?

(And no, I havn't managed to work all the way through you "QM" section.
After a while you just lost me completely. I'm hoping Hal's questions
will help clarify things enough for me to get a grip on it.)

Paddy Leahy
Received on Mon Jun 06 2005 - 07:34:33 PDT