Re: momentary and persistent minds

From: Nick Bostrom <>
Date: Thu, 11 Jun 1998 03:40:27 +0000

Wei Dai wrote:

> On Tue, Jun 09, 1998 at 04:13:22AM +0000, Nick Bostrom wrote:
> > Only if you believe in the many-worlds interpretation. A believer in
> > the MWI will have to add the idea of a measure, and say:"I will
> > observe X" with amplitude psi(x), and "I will observer Y" with
> > amplitude psi(y). This can then be translated into probabilities by
> > squaring the amplitude.
> I'm not sure what you mean. How does it differ from what I suggested?

I'm not sure it does, except that it is a clarification of an earlier
suggestion I made that you objected to:

> On Fri, May 29, 1998 at 04:03:00AM +0000, Nick Bostrom wrote:
> > It seems we can interpret "I will observe X" as meaning: "There is
> > a future brain-state B2, similar in certain respects to the
> > brain-state B1 which instanciates this present cognition C1, such
> > that B2 instanciates C2, and C2 includes an observation of X.".
> That is not going to give you nice results. For example if there is
> no wavefunction collapse, all possible brain-states exist in the
> future and "I will observe X" would have probability 1 for all X
> under your interpretation.

Do you think that the interpretation I mention works for non-quantum
situations? (Instead of saying "...similar in certain respects...", I
would now say "...standing in a certain relation R to...", since in
some theories of personal identity R will involve more than

If I am copied, then, depending on the details of the execution and
on R, there might either be one or two brains belonging to my future
self. The two brains might even have different perceptions. If they
both belong to my future self, I should have to say that I will have
multiple perceptions.

Now, if we want to combine this with the many-worlds interpretation,
we have to take into account that both the future brains may be in
superpositions, i.e. they might be instanciated in many different
real worlds. Will all these different brains, existing in different
worlds, belong to the same person? -- That depends on how different
these brains are from one another and on R. So whether "I will
observer X" has probability 1 in my interpretation depends on what
specific case you have in mind and on your theory of personal

Nicholas Bostrom
Department of Philosophy, Logic and Scientific Method
London School of Economics
Received on Wed Jun 10 1998 - 19:54:50 PDT

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