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

From: Russell Standish <>
Date: Thu, 9 Jun 2005 14:54:29 +1000

On Thu, Jun 09, 2005 at 01:55:32AM +0100, Patrick Leahy wrote:
> [Russell Standish wrote]:
> >The AP is a statement that observed reality must be consistent with
> >the observer being part of that reality.
> Famously, this can be interpreted as either a trivial tautology (Brandon
> Carter's original intention, I think), or an almost-obviously false
> principle of necessity (Barrow & Tipler's SAP). If you think there's a
> mystery here it suggests you go for the necessity version, but given your
> infinite ensemble the tautology would suffice perfectly well.

Yes, if you think there is a concrete reality in which everything
exists (your question of where does the observer live?), then the AP
is a tautology.

However, if you are prepared to allow for the possibility that
observers exist "nowhere", then things are not quite so simple. One
can always imagine being the brain-in-the-vat observer a reality which
does not contain a body, or a brain, in a vat or anywhere
else. Usually in this scenario, the observer will conclude that there
must be a body somewhere else, and so concludes that it is inhabiting
some kind of virtual reality. However, this implicitly assumes there
has to a brain somewhere, and so implies a reality somewhere else for
the brain to inhabit. But what if the brain is not required?

Obviously, the last conclusion is full blown solipsism, but that is
hardly a knock down argument.

Instead, one can take the Anthropic Principle as an assertion of the
reality we inhabit, and experimentally test it. In all such cases is
has been shown to be true, sometimes spectacularly. With the AP, one
recovers some of the properties of a concrete reality, without all of
it. In particular, Marchal's "shared dreaming" follows as a
consequence, and it contradicts solipsism.

> You also said:
> >>>The observer _is_ the interpreter. There may well be more than one
> >>>observer in the picture, but they'd better agree!
> >>
> >>Why does this follow? <snip>
> >
> >It follows from the Anthropic Principle. If O_1 is consistent with its
> >observed reality, and O_2 is consistent with its observed reality, and
> >O_1 observes O_2 in its reality, then O_1 and O_2 must be consistent
> >with each other (at least with respect to their observed realities).
> Ah. Just to be sure, do you mean that the string the observer "attaches
> meaning to" is the one which describes the very same observer? This seems
> to be implied by your comment above; but you don't say it or clearly
> imply it in your paper.
> Then you are implying that the observer can, in a finite time, read and
> attach meaning to a full (space-time) description of itself, including the
> act of reading this description and so on recursively.

Not at all. Consistency is the only requirement. If the observer goes
looking for erself, then e will find erself in the description. It
doesn't imply the observer is doing this all the time.

> Which is impossible, of course.

Of course.

> You also said:
> >I'm not entirely sure I distinguish your difference between "external
> >world" and "internal representation". We're talking about observations
> >here, not models.
> I'm sure you can distinguish *my* mental representation of the world from
> your own. Hence if we share a world, and you can't distinguish between
> that world and your internal representation, then you are not granting
> equal status to other observers such as me.

I'm not sure that is the case. I have a theory of your mind. I get it
most economically by observing my own mind, hence I'm self-aware. My
theory of the mind says that you are doing the same thing. Isn't this

> You also said (quoting me):
> >>My problem is that you are trying to make your observers work at two
> >>different levels: as structures within the universes generated
> >>(somehow!) by your bitstrings, but also as an interpretive principle
> >>for producing meaning by operating *on* the bitstrings. It's a bit
> >>like claiming that PCs are built by "The Sims".
> >
> >Yes it is a bit like that. Obviously, the Anthropic Principle (or its
> >equivalent) does not work with "The Sims".
> Actually I don't see why not. The existence of The Sims implies a universe
> compatible with the existence of Sims. But granting this is not so for the
> sake of the argument, presumably the AP *will* apply to the Sims Mark VII
> which will be fully self-aware artificial intelligences.

If the AP applies to the Sims Mark VII, then their reality will be a
description containing a "body" corresponding to their
intelligences. They will not be aware of the PC that their description
is being generated on. We, who inhabit the world with the PC will not
be aware of the countless other PCs, Macs, Xboxes, Eniacs, Turing
machines, pebbles in Zen monasteries etc running Sims Mark VII. So the
PC itself is actually irrelevant from the internal perspective of the Sims.

> But it will still
> be absurd to claim that the Sims are responsible for construction of PCs
> (assuming they are not connected to robot arms etc, for which no analogs
> exist in your theory). Let alone for them to construct the actual PC on
> which they are running, as apparently implied by your last message... even
> robot arms wouldn't help there.

No, it is called stretching an an analogy too far!

> Paddy Leahy
> ======================================================
> Dr J. P. Leahy, University of Manchester,
> Jodrell Bank Observatory, School of Physics & Astronomy,
> Macclesfield, Cheshire SK11 9DL, UK
> Tel - +44 1477 572636, Fax - +44 1477 571618

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Received on Thu Jun 09 2005 - 02:08:44 PDT

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