On Oct 27, 12:10 am, Russell Standish <li...@hpcoders.com.au> wrote:
> On Tue, Oct 25, 2011 at 04:00:56PM -0700, Nick Prince wrote:
> > QTI, Cul de sacs and differentiation
> > I’m trying to get a picture of how David Deutsch’s idea of
> > differentiation works – especially in relation to QTI. >
> I'm persona non grata on FOR, so must respond on the everything-list.
> In section 8.1.3 of my book, I characterised David Deutsch's position
> as a "single tracks through the multiverse". Namely that there is a
> fact of which future history you will have (preordained as it were),
> even if it is impossible to know it.
> There has been quite a bit of discussion of "fungibility" recently,
> and I'm now up to the section of BoI where David discusses this. I'm
> inclined to think that the concept of fungibility really changes the
> picture - namely one should think of the "single tracks through the
> multiverse" as being fungible up until the point where they
> differentiate. Being fungible, would entail the supervention of
> consciousness on all fungible histories, and the full force of the QTI
> conclusion. It would be interesting to hear (from David, or other
> people) whether:
> a) What David's position is now (are our futures determined or not?)
> b) Was my characterisation of David's position was ever valid?
> c) If so, and David's position has changed, what persuaded him to
I’ve just read through the multiverse chapter in BOI and found it
hard to get a handle on some of the concepts. I changed over to
thinking in terms of differentiation rather than splitting worlds (of
De Witt and Price's FAQ) when I read FOR quite a while ago but your
book and this list helped me understand it better (I think?). I’m
not sure that my understanding of fungibility is the same as DD’s now
either - in fact I'm now confused. Neither am I sure about the nature
of determinism in the interpretation.
I started to read some of the earlier posts on fungibility on the BOI
list and found the opinions so contradictory that I got lost. If you
or anyone can give a concise definition of this term then I would be
My own view was that a “bundle” of completely identical universes are
fungible. If however I (who am in all these universes) send an
electron with spin in the |X+> into a SG device aligned in the Z+
direction, then, after this procedure, the universes will no longer
be fungible with respect to the original bundle. Because roughly half
of these universe will now contain an electron with spin Zup that is
in a different state to the other half containing the electron with
spin Zdown. However, each of these two new bundles will be fungible
internally with respect to themselves in that each of the bundles will
have identical universes in them. Hence identical universes in the
multiverse are fungible up until the point where they differentiate
into newly, internally fungible bundles. Have I got this right?
DD talks in his book about universes that are identical, symmetrical
and deterministic which would never become differentiated unless they
were fungible. He points out that the processes which allow these
differentiations are due to QM as in the SG case above. So, I read
this to mean that it is the indeterminism (within universes) of QM
that is at the root of fungibility! Have I got this right? (I didn't
think it was the transporter anyway :)
I agree that the Multiverse as a whole, and, because of linearity,
individual universe instantiations would be deterministic (follow the
SE eqn.) - but not from the ist person point of view of those within
the universes. Maybe that is what he means but I have misread it?
Also on p453 of BOI, I think DD says his guess regarding the (required
additional) assumption underlying QSuicide survival is that it is
PS I sent a version of this post to the BOI list too
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