On 21 December 2011 22:24, Russell Standish <li...@hpcoders.com.au> wrote:

> Its a fair point, but let me answer this way: The observer experience
> must be of a single branch - this is effectively the definition of a
> branch. However, this is not the same as saying the observer must
> supervene on a single branch, if it supervenes at all. Supervenience
> just means that if my experience differs, then whatever I supevene on
> must differ also. Supervenience over multiple branches is not apriori
> nonsense. For example, it may not be possible to slice multiverse
> branches in any objective sense (David Deutsch's fungibility
> argument). In which case, supervenience must be across all branches
> that make up an observer moment.
>
> My point is simply that Maudlin's argument only rules out
> supervenience on a single branch, assuming COMP. To rule out
> supervenience on multiple branches requires a different set of
> considerations, and I'm not convinced by Bruno's dovetailer approach
> to this.

Thanks for this Russell, but I'm still puzzled.  As you say above, in
a MW version of Maudlin's argument "supervenience must be across all
branches that make up an observer moment".  These branches are in
effect fungible, or equivalent, with respect to a particular observer
moment.  By the same token, branches outside this collection must be
associated with different moments ("if my experience differs, then
whatever I supervene on must differ also").  Consequently, isn't it
still the case that the branches on which any particular moment
supervenes, and which therefore constitute Maudlin's "classically"
deterministic trivial device, specifically exclude all counterfactual
outcomes (i.e. different moments)?  If this is so, such excluded
branches can hardly be appealed to as part of the justification for
the content of the moment in question, as Maudlin, in effect, argues.

I feel I may be still missing some vital aspect of your argument.
Perhaps you are arguing that the consciousness of an "observer" in a
MW scenario must supervene on ALL branches, despite the fact that only
one of the available experiences is ever personally accessible as a
given observer moment.  But couldn't an expanded version of Maudlin's
argument still reduce this in effect to a collection of experiences
supervening on a corresponding collection of individually trivial
"devices"?  And if so, if his argument from triviality is persuasive
for one device, how is it less so for the collection?

David

> On Wed, Dec 21, 2011 at 01:06:45PM +0000, David Nyman wrote:
>>
>> Russell, isn't it central to the multiverse view that distinct,
>> univocal observer experiences supervene on each branch?  In which
>> case, isn't it correct to apply Maudlin's argument to each branch
>> separately?  If so, to oppose the conclusion by appealing to all the
>> branches simultaneously might seem like wanting to have your cake and
>> eat it too.
>>
>> David
>>
>
> Its a fair point, but let me answer this way: The observer experience
> must be of a single branch - this is effectively the definition of a
> branch. However, this is not the same as saying the observer must
> supervene on a single branch, if it supervenes at all. Supervenience
> just means that if my experience differs, then whatever I supevene on
> must differ also. Supervenience over multiple branches is not apriori
> nonsense. For example, it may not be possible to slice multiverse
> branches in any objective sense (David Deutsch's fungibility
> argument). In which case, supervenience must be across all branches
> that make up an observer moment.
>
> My point is simply that Maudlin's argument only rules out
> supervenience on a single branch, assuming COMP. To rule out
> supervenience on multiple branches requires a different set of
> considerations, and I'm not convinced by Bruno's dovetailer approach
> to this.
>
> --
>
> ----------------------------------------------------------------------------
> Prof Russell Standish                  Phone 0425 253119 (mobile)
> Principal, High Performance Coders
> Visiting Professor of Mathematics      hpco...@hpcoders.com.au
> University of New South Wales          http://www.hpcoders.com.au
> ----------------------------------------------------------------------------
>
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