Re: Devil's advocate against Max Tegmark's hypothesis

From: Christopher Maloney <>
Date: Wed, 07 Jul 1999 23:36:37 -0400

Higgo James wrote:
> Let's be clear about the flying rabbit: we have chosen it as a proxy
> for something very unusual. Otherwise we would have said 'flying bat' which
> is unusual but not very unusual. So we are really asking, 'why is something
> we have chosen to be very unusual, very unusual?'. I fail to see the
> relevance of this piece of circular reasoning.
> All it amounts to is asking why there is any stability in our
> observations, and I think you need nothing more than the weak anthropic
> principle to explain stability.

I disagree with this, although it is very well put. It is true that
the question "why is something we have chosen to be very unusual, very
unusual?" is circular and useless. But that's not the way I read the
"flying rabbit" problem. Let me try to be precise about the way I
interpret the problem. I'd very much like it if people could comment
on this, since I don't feel that I'm very clear, yet, about the
terminology used on this group, in particular, relative
strong-Self-Sampling Assumption (SSSA)" and "Strong SSSA" (did you
really mean "strong strong self-sampling assumption, Bruno?).

No matter what is meant by the term "existence", one can say that
there is some number, probably infinite, of conscious observer
moments in existence. The weak anthropic principle would suggest
that we find ourselves in a set of those which are "not very special".
This is the SSA. So the natural next step is to examine the
properties of ourselves that we can identify, and try to determine if
that principle holds.

To define "not very special", we need to establish some kind of
measure over the set of possible universes, and thus, in theory, over
the set of all existing observer-moments (I just made the assumption
that possible == exists, which is a tenent of this group). This
brings us to the question which was posed in the very first post to
this group, by Wei Dai: how do we establish this measure?

Now, one of the properties of our conscious existence which is
identifiable is that causal relations seem to hold. That is, we don't
see flying rabbits, because in flying is caused by flapping wings, and
rabbits don't have wings (to quote Monty Python, they don't so much
fly, as plummet). But modern physics tells us that causal relations
only hold in a statistical sense. That is, our science can only give
relative probabilities that things will happen. This is true in the
quantum as well as in the classical domain, it's just that in the
classical domain, the probabilities become ridiculously large (or
small) depending on the phenomenon that is studied.

But why should causal relations *seem* to hold at all? This was the
problem posed by Hume. Why should there be any connectedness between
one moment of time and another, or between our memories and physical
reality? It would seem plausible that among the set of all possible
(hence existing) conscious observer moments, there are a fair number
that just are, without having been caused by anything, and that are
in existence in nonsense universes. Even in this universe, there
is a non-vanishing probability that a rabbit will materialize out of
the thin air, and fly (for however brief a moment) through the room.
Why is it be that the probability of this is what it is, i.e.
extremely low? Granted we picked, on purpose, a scenario which we
know to be unlikely. But the question is, why are the probabilities
what they are?

So the "flying rabbit" problem is just a restatement of the "why are
there physical laws" question, which has also been debated on this
list myriads of times. I do agree with Jacques M. Mallah that this
group desperately needs a FAQ, especially to tie different approaches
to the same questions together.

Chris Maloney
"Knowledge is good"
-- Emil Faber
Received on Wed Jul 07 1999 - 21:01:58 PDT

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