On Jun 15, 1:27 pm, Russell Standish <[EMAIL PROTECTED]> wrote:
> What sparked our/my interest is that you seemed to have
> interesting argument against the use of anthropic reasoning.
I'm certainly not arguing against *all* anthropic reasoning; every
argument needs to be examined on a case by case basis.
> on reflection it seems to boil down to "there is no mysterious
> pre-world of souls hanging around waiting the be born, so there is no
> distribution of observers to be sampled from". I disagree with this syllogism.
This is where reasoning about conventional cosmology departs from
reasoning about all-universe models. In the latter context, it might
make sense to consider "myself, right now" as comprising a vast number
of instances who have identical current experiences, but whose next
experience will be different for different instances. I might then
concern myself with adopting a strategy that will benefit a majority
of my instances, and which can exploit the fact that those instances,
in their totality, obey some distribution. In that context, there
certainly is a distribution of observers to be sampled from.
But in conventional cosmology, although observers of this form are a
possibility, they're not a given. If I really am living, solely, on
one particular planet at one particular time, then I have never
sampled the distribution of all observers in the history of the
universe, and nothing about my experience can tell me anything about
that distribution (beyond the fact that I, and my fellow humans,
belong to it).
> Assuming for the sake of argument that I can be viewed as a random
> sample of the global population, how does this actually help to
> distinguish theory A or B, unless I actually received less than X
> kJ/day, which, by assumption is not the case. I don't see how
> anthropic reasoning makes a difference in this case.
I probably haven't made my point very clearly here. What I'm arguing
against is what you wrote previously:
> My attributes (eg
> height, weight and so on) are all drawn from distributions of such
> attributes. Why not some hypothetical property like "observer class"
> as set up in this toy problem?
Why is your height and weight drawn from a certain distribution? It's
because you've been exposed to certain statistical influences on those
attributes, and those influences are influences that you have in
common with a certain subset of the human population. But it would be
absurd to say that *your* height and weight is drawn from the
distribution of heights and weights of all living creatures in the
history of the universe. Equally, it would be absurd to say that your
observer class has been drawn from the distribution of all observers
in the history of the universe.
> > Ultimately this boils down to locality. I, here and now, do not know
> > the future, so of course I can't discriminate between rival theories
> > that make identical predictions about the present but different
> > predictions about the future.
> But we do this all the time. Why is it we reject crackpot claims that
> the world will end on such and such a date for instance?
We reject those claims because they flow from theories that we reason
should have led to observable consequences in the past (e.g. theories
of interventionist deities). So what we have are prior probabilities
that strongly disfavour those crackpot theories -- and given equal
crackpot ratings, their predictions about the future are irrelevant.
If crackpot A tells me that the world will end in 2012, and crackpot B
tells me that the world will end in 20,012, then all else being equal
I will (in 2008) give them both *equal* low credence.
And given two (non-crackpot) cosmological theories with equal
grounding in modern physics and which imply no observable differences
up to the present epoch, but wildly different consequences in the very
far future, we *cannot* use those far-future consequences to
discriminate between them. Specifically, we cannot use differences in
the numbers of future observers in various classes that the different
theories predict, in order to favour one theory over another, here and
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