Re: Request for a glossary of acronyms

From: Saibal Mitra <>
Date: Fri, 6 Feb 2004 14:41:06 +0100

----- Original Message -----
From: Jesse Mazer <>
To: <>
Sent: Thursday, February 05, 2004 12:19 AM
Subject: Re: Request for a glossary of acronyms

> Saibal Mitra wrote:
> >
> >This means that the relative measure is completely fixed by the absolute
> >measure. Also the relative measure is no longer defined when
> >are not conserved (e.g. when the observer may not survive an experiment
> >in quantum suicide). I don't see why you need a theory of consciousness.
> The theory of consciousness is needed because I think the conditional
> probability of observer-moment A experiencing observer-moment B next
> be based on something like the "similarity" of the two, along with the
> absolute probability of B. This would provide reason to expect that my
> moment will probably have most of the same memories, personality, etc. as
> current one, instead of having my subjective experience flit about between
> radically different observer-moments.

Such questions can also be addressed using only an absolute measure. So, why
doesn't my subjective experience ''flit about between radically different
observer-moments''? Could I tell if it did? No! All I can know about are
memories stored in my brain about my ''previous'' experiences. Those
memories of ''previous'' experiences are part of the current experience. An
observer-moment thus contains other ''previous'' observer moments that are
consistent with it. Therefore all one needs to show is that the absolute
measure assigns a low probability to observer-moments that contain
inconsistent observer-moments.

> As for probabilities not being conserved, what do you mean by that? I am
> assuming that the sum of all the conditional probabilities between A and
> possible "next" observer-moments is 1, which is based on the quantum
> immortality idea that my experience will never completely end, that I will
> always have some kind of next experience (although there is some small
> probability it will be very different from my current one).

I don't believe in the quantum immortality idea. In fact, this idea arises
if one assumes a fundamental conditional probability. I believe that
everything should follow from an absolute measure. From this quantity one
should derive an effective conditional probability. This probability will no
longer be well defined in some extreme cases, like in case of quantum
suicide experiments. By probabilities being conserved, I mean your condition
that ''the sum of all the conditional probabilities between A and all
 possible "next" observer-moments is 1'' should hold for the effective
conditional probability. In case of quantum suicide or amnesia (see below)
this does not hold.

> Finally, as for your statement that "the relative measure is completely
> fixed by the absolute measure" I think you're wrong on that, or maybe you
> were misunderstanding the condition I was describing in that post.

I agree with you. I was wrong to say that it is completely fixed. There is
some freedom left to define it. However, in a theory in which everything
follows from the absolute measure, I would say that it can't be anything
else than P(S'|S)=P(S')/P(S)

> the multiverse contained only three distinct possible observer-moments, A,
> B, and C. Let's represent the absolute probability of A as P(A), and the
> conditional probability of A's next experience being B as P(B|A). In that
> case, the condition I was describing would amount to the following:
> P(A|A)*P(A) + P(A|B)*P(B) + P(A|C)*P(C) = P(A)
> P(B|A)*P(A) + P(B|B)*P(B) + P(B|C)*P(C) = P(B)
> P(C|A)*P(A) + P(C|B)*P(B) + P(C|C)*P(C) = P(C)
> And of course, since these are supposed to be probabilities we should also
> have the condition P(A) + P(B) + P(C) = 1, P(A|A) + P(B|A) + P(C|A) = 1 (A
> must have *some* next experience with probability 1), P(A|B) + P(B|B) +
> P(C|B) = 1 (same goes for B), P(A|C) + P(B|C) + P(C|C) = 1 (same goes for

> C). These last 3 conditions allow you to reduce the number of unknown
> conditional probabilities (for example, P(A|A) can be replaced by (1 -
> P(B|A) - P(C|A)), but you're still left with only three equations and six
> distinct conditional probabilities which are unknown, so knowing the
> of the absolute probabilities should not uniquely determine the
> probabilities.

Agreed. The reverse is true. From the above equations, interpreting the
conditional probabilities P(i|j) as a matrix, the absolute probability is
the right eigenvector corresponding to eigenvalue 1.

> >Let P(S) denote the probability that an observer finds itself in state S.
> >Now S has to contain everything that the observer knows, including who he
> >is
> >and all previous observations he remembers making. The ''conditional''
> >probability that ''this'' observer will finds himself in state S' given
> >that
> >he was in state S an hour ago is simply P(S')/P(S).
> This won't work--plugging into the first equation above, you'd get
> (P(A)/P(A)) * P(A) + (P(B)/P(A)) * P(B) + P(P(C)/P(A)) * P(C), which is
> equal to P(A).
You meant to say:

''P(A)/P(A)) * P(A) + (P(A)/P(B)) * P(B) + P(A)/P(C) * P(C), which is not
 equal to P(A).''

This shows that in general, the conditional probability cannot be defined in
this way. In P(S')/P(S), S' should be consistent with only one S. Otherwise
you are considering the effects of amnesia. In such cases, you would expect
the probability to increase.

Received on Fri Feb 06 2004 - 08:45:19 PST

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