Re: RS and RSSA

From: Russell Standish <>
Date: Wed, 5 Jul 2000 11:57:41 +1000 (EST)

Jacques Mallah wrote:
> >From: RS <>
> >I finally had a bit of a chance to glance through Nick's thesis. I
> >guess Nick stayed out of the ASSA/RSSA debate for good reasons.
> >
> >His SSSA introduced SSA over observer moments, so one could rightly
> >say that the ASSA and the RSSA are both examples of SSSA. Note the
> >SSSA clearly states that the reference class includes all observer
> >moments that don't differ by any relevant respect.
> I guess what's "relevant" is the question.
> >With the ASSA, the reference class is all observer moments belonging to a
> >particular individual (rooted at that individual's birth, lets say).
> At this point I have to ask - what are you smoking? Because I don't
> want any.
> With the ASSA, the reference class is just all observer-moments.
> (Weighted according to number, or measure. i.e. Fully identical twins
> (supposing that were possible) still have double the measure of one man.)
> Of course additional conditionals are added as appropriate for a particular
> question. (i.e. If I ask "What is the effective probability of seeing X
> given that I see Y", then you could say OMs that see Y is the reference
> class.) (Example: X="my age>50", Y="I am human".
> p(X|Y) = M(X and Y)/M(Y).)
> Note: important point: the ASSA does not, in any way, shape or form,
> single out the notion of "a particular individual" as having any
> significance whatsoever. That is one advantage it has over the RSSA, and
> one I have harped on many a time, so it's surprising you don't know that.

For many of us, this is a distinct disadvantage, as it is not clear
that the reference class of all observer moments is all that well
defined. I agree that it can be applied to the set of all human
observer moments reasonably unambiguously. If you wish, we can do
that, it doesn't change my critique one bit. However, I fail to see what
your issue is with the notion of an individual (tree of observer
moments rooted at birth).

> >With RSSA,the reference class is the set of all future moments adjacent to
> >a given observer moment. All of this assumes that a temporal partial
> >ordering in fact exists between observer moments.
> I guess the RSSA assumes that. (ASSA doesn't, although I also believe
> in time.) Your above definition of RSSA is unclear.

No, the ASSA doesn't need this, but for purposes of comparison, we
need to work with time. I have stated my reasons before why I regard
time as essential for observers (and consequently observer moments) to
exist. Why is the above definition unclear? For discrete observer
moments linked by temporal partial ordering, it is perfectly
clear. Taking the continuum limit looks fairly unproblematic at this
point in time.

> >With the ASSA, the measure attached to a particular observer moment is
> >related to the complexity of that observer moment, ie how much history
> >is contained within it.
> Not necessarily related to complexity, but with the AUH there is a
> relation. Definitely not related to the amount of history; that's just
> depth, not complexity. Grab a Li & Vitanyi if you don't know what I mean.

I know exactly what you mean. However, at each "branching" event of
the MWI, information/complexity is added to the history because of the
stochastic outcomes. Only if the outcomes are fully deterministic is
complexity not increased, but depth is.

> >It can also be computed by integrating the
> >RSSA values from birth over the history that leads up to that observer
> >moment. Several histories may need to be integrated over in the case
> >of forgotten events.
> An interesting statement on your part. Here, you seem to be saying that
> the absolute measure does in fact exist.

Up to a point. Given an initial condition to the universe (its big
bang), then measure of outcomes (aka observer moment) from any history
rooted in that initial condition is a well defined "absolute" measure.

However, I doubt that an absolute measure exists over the whole
Plenitude. Certainly, the Solomon-Levin Universal prior does not live
up to the bargain.

> >It would seem to me that when discussing expected self-observed age,
> >the ASSA is the wrong reference class, here age is a relevant
> >variable. However, the ASSA treats all observer moments of a given
> >individual throughout its lifetime as equivalent. Surely this is wrong.
> The only thing that's wrong is your understanding of the ASSA and of
> related matters.

Unhelpful comment. Where, exactly, do you think my understanding is wrong?

> - - - - - - -
> Jacques Mallah (
> Physicist / Many Worlder / Devil's Advocate
> "I know what no one else knows" - 'Runaway Train', Soul Asylum
> My URL:
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Dr. Russell Standish Director
High Performance Computing Support Unit, Phone 9385 6967
UNSW SYDNEY 2052 Fax 9385 6965
Room 2075, Red Centre
Received on Tue Jul 04 2000 - 18:51:27 PDT

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