Re: Dualism and the DA

From: Bruno Marchal <>
Date: Fri, 24 Jun 2005 16:07:34 +0200

Le 22-juin-05, à 13:19, Brent Meeker a écrit :

>> -----Original Message-----
>> From: Bruno Marchal []
>> Sent: Wednesday, June 22, 2005 8:16 AM
>> To: Pete Carlton
>> Cc: EverythingList
>> Subject: Re: Dualism and the DA
>> Le 21-juin-05, à 21:21, Pete Carlton a écrit :
>>> <snip>
>>> Now, if you introduce copies to this scenario, it does not seem to me
>>> that anything changes fundamentally.  Your choice on what kind of
>>> scenario to accept will still hinge on your desires for the future of
>>> any persons involved.  The desires themselves may be very
>>> complicated,
>>> and in fact will depend on lots of hitherto unspecified details such
>>> as the legal status, ownership rights, etc., of copies.  Of course
>>> one
>>> copy will say "I pushed the button and then I got tortured", and the
>>> other copy will say "I pushed the button and woke up on the beach" -
>>> which is exactly what we would expect these two people to say.  And
>>> they're both right, insofar as they're giving an accurate report of
>>> their memories.  What is the metaphysical issue here?
>> There are two *physical* issues here.
>> 1) The simplest one is that if you agree with the comp indeterminacy
>> (or similar) you get an explanation of the quantum indeterminacy
>> without the collapse of the wave packet. This is mainly Everett
>> contribution.
> I think Pete has a good point; I don't see how this bears on his
> analysis of
> "I".

Could you elaborate a little bit? I don't see how it could possibly
not bear on Pete's analysis of "I". I mean if Pete is right about his
"I", he should agree with Everett's notion that the probabilities are
subjective in QM.

>> 2) The less trivial one, perhaps, is that if you agree with the comp
>> indeterminacy you get an a priori explosion of the number of
>> appearances of first person white rabbits
> I don't see that either. The SWE doesn't predict that *everything*
> (which is
> what I presume you to mean by "white rabbits") will happen. If it did
> it would
> be useless.

Once you accept comp, the "explosion of rabbits" follows from the UD
Argument (UDA). Invoking the SWE here is irrelevent, unless to say that
the SWE is the only way to solve the rabbits problem. Showing this from
comp only would be derivation of the SWE from comp.

>> and the only way to solve
>> this, assuming the SWE is correct, must consist in justifying the SWE
>> from the comp indeterminacy bearing
> But the "indeterminancy" of comp arises from equivocation about "I" as
> Pete
> noted.

I can agree with the use of such vocabulary.

> It assumes first that there is an "I" dependent on physical structure

The "physical structure" is what makes an "I" to be able to manifest
eself relatively to some probable computation.

> and then sees a problem in determining where the "I" goes when the
> structure is
> duplicated.


>> on all computational
>> states/histories.
> The fact that all these metaphysical problems and bizarre results are
> predicted
> by assuming *everything happens* implies to me that *everything
> happens* is
> likely false.

1) Weirdness is not falsity, but ok I am open we will get a falsity
from comp, and then comp will be refuted and that would be a giant
2) "everything happens" in the comp frame, just means that the set of
all possible computations is as well defined as the set of natural
numbers. You cannot make disappear a computation for the same reason
you cannot dismiss the number "13" or the least prime bigger than

> I'm not sure what the best alternative is, but I like Roland
> Omnes view point that QM is a probabilistic theory and hence it must
> predict
> probabilities for things that don't happen.

OK, but that is an ad hoc "wishful thinking" move to preserve unicity
of history. Even Roland Omnes agrees that such a move is non cartesian.
And then, in the french edition (but not in the english edition if I
remember correctly-I will verify again!) he opposes Heidegger against
Descartes in the most irrational way.

Received on Fri Jun 24 2005 - 10:10:52 PDT

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