Re: Dualism and the DA (and torture once more)

From: Bruno Marchal <>
Date: Mon, 20 Jun 2005 12:57:05 +0200

Le 19-juin-05, à 02:39, Jonathan Colvin a écrit :

> I'm sure the one in Moscow will also answer that he feels really to be
> the
> one in Moscow.


> But what you haven't answered is in what way the universe is
> any different under circumstance (A) than (B). This is because there is
> surely *no* difference at all.

There is no 3-difference at all, but only a God can know that. There is
a first person difference: it is the difference between writing in my
personal diary "oh I'm in Moscow" and "oh I'm in Washington".
Note that here we can understand why the question "why I am the one in
W" or "why I am the one in M" are 100% meaningless. This does not
entail that the question where will I be in the next duplication is

> This is the reason why it makes no sense (to me) to take the position
> that
> if I copy myself, there is a 50% chance of (A) me being observer A,
> and a
> 50% chance of (B) me being observer B. There is no difference between
> (A)
> and (B).

This is because you look at the experiment only from the third person
point of view. Suppose we iterate the self-duplication 64 times. Among
the 2^64 copies most will acknowledge that they are "living" a random
experiment (it can be shown that most of the 2^64 sequence of W and M
(or 1 and 0) are kolmogorov-chaitin-solovay incompressible.
For them, that is from their first person point of view, they are in a
state of maximal indeterminacy and their best theories will be that
they are confronted to a Bernouilli random experience. Of course,
taking your God-like point of view you can tell them that they are
under an illusion, giving that there is no 3-person difference (as God
knows). Let us call that illusion "the first person experience" and let
us try to explain it. The illusion exists, unless comp is false and the
reconstituted people are zombies.

> This is also the reason why I choose (A) a 50% chance of torture over
> (B)
> being copied ten times, and one copy getting tortured (where it is
> suggested
> there is only a 10% chance of me getting tortured).

Remember that for me this sort of reasoning always suppose no future
merging or duplication and also that the copies have sufficiently
diverge (and then the exact computation is most probably intractable,
like in "real physics").

> There are clearly two
> different possible universes under (A) (one where I get tortured, one
> where
> I don't). Under (B), there is no way I can make sense of what the 10%
> probability applies to. The universe is identical under situation (a)
> I'm
> person 1 who gets tortured and (b) I'm person 2-10 who doesn't.

I am with you here. and if you agree with the 50% I made my point. The
10% was introduced only for treating a case where the copies did not
diverge (or the comp histories going through the states of those

> To insist that there *is* a difference surely requires some new kind of
> dualism. Perhaps it is a valid dualism;

Not this one. Only the duality between 1 and 3 person is valid.

> but I think it should be accepted
> that theories reifying the 1st person are fundamentally dualistic.

The word "dualism" is a little too vague. Once you agree with the 50%
for a WM duplication, you accept the only sort of dualism I defend, but
it is more an epistemological dualism than an ontological one. It is
about *knowledge* not *being* (still less substance).
This means you accept the step 3 of the Universal Dovetailing Argument
Explanations in english:

> But I
> know what your response will be..the dualism comes from reifying the
> 3rd
> person independent universe, and if we accept only the 1st person as
> "real",
> there is no dualism. It is quite a metaphysical leap, though, to
> discard the
> 3rd person universe. I'd like to know how to justify such a shift.

Careful, you are the one making a "big leap", here. You go from the "
3th step to the 8th step in the Universal Dovetailing Argument. I don't
pretend it is easy or obvious. But it is not a metaphysical leap, it is
a logical conclusion, once we take the comp hyp seriously enough, and
this without hiding the 1-3 distinction under the rug.

> It does not seem simpler by Occam, because instead of 1 universe
> containing
> many observers, we have a multiplicity of universes, each with 1
> observer.

We have a multiplicity of well defined computations, all statically
existing in the arithmetical Platonia. It is simpler by occam (QM also
presupposed those computations). Some computations can be seen as
histories by internal self-referential inference inductive machine.

> How does this differ from solipsism?

Please believe me, if comp leads to solipism, I will take it as a
powerful argument against comp. But that would be currently highly
premature. The logical possibility that comp makes solipsim false is
due to the nuance between first person point of view (as I describe it
through the duplication experiment) and the first person plural point
of views, where the duplications operate on collection of people
sharing some computation. Why such 1-plural views win in the limit of
the universal dovetailing is still an open problem. But then the non
triviality of the consequences of Church thesis and theoretical
computer science gives (technical) evidences for such notion.

> How do we make sense of other observers within *our* universe?

A little like when you play a video games with other people, you can
bet on them.

> If there questions have been addressed before on the list, feel free to
> point me to the relevant archive section.

UDA on the list:

UDA step by step on the list (links):
UDA step 1
UDA step 2-6
UDA step 7 8
UDA step 9 10
UDA last question
Joel 1-2-3
Re: UDA...
Joel's nagging question

But I think it is still better done in my sane paper refered above.
(Other links are in my url).

Received on Mon Jun 20 2005 - 07:23:45 PDT

This archive was generated by hypermail 2.3.0 : Fri Feb 16 2018 - 13:20:10 PST