[ExI] against Many Worlds QT

Stathis Papaioannou stathisp at gmail.com
Mon May 18 14:44:31 UTC 2009

2009/5/18 Eschatoon Magic <eschatoon at gmail.com>:

> Interesting. Experiment should decide, as soon we can design
> experiments to assess Everett's MWI vs.other interpretations of
> quantum physics. In the meantime, all interpretations of quantum
> physics consistent with experiment are, indeed, interpretations:
> different labels, conceptual models and intuitive visualizations for
> the same set of experimental results.
> Without having studied this paper in detail I would hazard that the
> references to things like "utilitarianism, or any other strategy, is
> the unique rational way of optimizing the welfare of one’s own, and
> other people’s, many future selves in a multiverse" seem a bit out of
> place. The universe does not know, or care, of rationality, morality
> and our welfare. It just does its own thing, and it is up to us to
> find useful and workable models for its behaviour.

The author seems to be arguing that many worlds should allow the
possibility of using all sorts of strange utility functions not
available to single world theories, and that this damages the case for
using decision theory to derive the Born rule in MWI, since one such
attempt to do so requires the (unjustified, it is claimed) adoption of
mean utilitarianism. The author also seems to have a problem with how
probabilities are deduced by observers in the MWI (or any multiverse
model). He points out that any observer following a sequence of random
events like coin tosses will conclude that the pattern he observes is
indicative of a particular bias that might not be there: someone will
definitely observe a sequence of 1000 heads, and that person will
conclude the coin is heavily biased, even though it isn't. But I don't
see how this is different to single world probability if you have a
large number of non-communicating experimenters tossing coins: a small
number might conclude that the coin is biased, but most will get
approximately 50/50 heads/tails, just as in the MWI.

The author discusses model multiverses which we could create with a
branching computer program, and uses these to support his contention
that probability doesn't work in the MWI. But *something* has to
happen in these models, if they are physically possible. That is, the
observers would come up with some sort of physical theory and account
of probability. It doesn't do to throw up one's hands and say that
probability becomes meaningless in these cases.

Stathis Papaioannou

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