This is a wonderfully clear explanation of Bruno's UDA. Perhaps Bruno could
confirm that it is what he intended.
As for the observer - or more fundamentally, the observer-moment - I think
you can get away without explicitly defining it. All you need is two
assumptions:
Firstly, you have to assume that observer-moments exist. I think it is
pretty clear that this is the case; you know it and I know it. You may not
know how to explain it, define it, or even describe it, but you definitely
know that observer-moments exist if you are a conscious being.
Secondly, you have to assume that this mysterious consciousness thing is
"Turing emulable". It is not nearly as obvious that this second assumption
is true, and biological chauvinists may continue to deny it no matter what
progress AI research may make. At some point, as Bruno says, you may have to
take "comp" on faith; for example, say "yes doctor" to the offer of a
durable new electronic brain when yours is starting to break down.
It should now be clear that if both of the above assumptions are true, then
the UD should generate all the observer-moments as per Bruno and Brian. The
"observer" is then a derivative entity, made up of certain subsets of
observer-moments. You know what an observer-moment is through direct
experience, but you have nowhere been forced to explicitly define it. If you
want to say that consciousness is something utterly mysterious forever, you
can say this, and the UDA still holds.
--Stathis Papaioannou
>From: Brian Scurfield <brian.scurfield.domain.name.hidden>
>To: "'Stephen Paul King'" <stephenk1.domain.name.hidden>
>CC: everything-list.domain.name.hidden
>Subject: RE: Everything Physical is Based on Consciousness
>Date: Fri, 06 May 2005 18:04:45 +1200
>
>In reply to Lee Corbin on the Fabric of Reality List
>----------------------------------------------------
>
>Lee,
>
>You gave us some wonderful examples of totally ridiculous Turing Machines
>that are nevertheless possible (I would at this point ask somebody to take
>away Charles' keyboard). You have noted that these TMs are improbable; we
>would not expect them to be instantiated in any great measure throughout
>the
>multiverse. They are similar to Harry Potter universes in this respect.
>Surely, though, the fact that they are improbable is not a blow against
>Bruno! His argument is concerned with measure and you are playing right
>into
>that. Let me try to explain...
>
>To make this easier, let's forget about physical reality for a while. Let's
>consider the Universal Dovetailer (UD). For those not in the know, the UD
>is
>a TM that systematically lists and executes all possible TMs. Because there
>are an infinite number of TMs, the UD cannot wait until all the TMs are
>listed before it executes them. It also cannot allow any one TM to
>monopolise the runtime, lest that TM never halts. So it must execute a step
>of one TM, then a step of another TM and so on, and it must do this while
>continuing to list the TMs. The first TMs off the list will be the simple
>ones - those with the shortest bitstrings and these are the first to be
>kicked off. Complex TMs with very long specifications will not be kicked
>off
>until much later. At any point in time in which they are still running,
>these complex TMs will have received less runtime than any simpler TM that
>is still running. This is important, as we shall see.
>
>As we have discussed, some (an infinite subset) of the TMs will support
>observers when they are executed. The observers and their worlds unroll as
>computational histories.
>
>What does an observer observe?
>
>It is important to see that the computational histories of different TMs
>can
>be identical up to a point and then diverge. So different TMs can produce
>the same observer history up to a point. The observer moment, then, is
>"simultaneously" generated by many different TMs. You can't pluck one
>history and say you are in that history. You are part of many identical
>histories that are about to diverge. And you can't pluck one TM and say
>that
>that is the TM that is instantiating you. Your history is generated by many
>different TMs. These are very important points. And, I think, the source of
>much confusion over Bruno's work.
>
>What an observer observes depends on all the computational histories their
>current moment is in and how the histories branch. The question also
>depends
>on what we mean by observer, but let's put that aside for now because I
>don't yet understand this part. Note that observer time has no relation to
>dovetailer time.
>
>Obviously, the computational history of a TM that consistently supports an
>observer can't be random. It must perform the computations necessary for an
>observer. Now the history might become random after the n-th step, at which
>point the observer no longer exists. Or the observer might morph into a
>completely different observer that has no memory of its former existence (I
>would argue that the observer is now a new observer). Or fluffy white bunny
>rabbits might appear. The TM's executing these histories first run an
>observer and then do something strange. Presumably this makes the TM more
>complex because the strangeness requires extra bits to specify. These TMs
>therefore get less runtime than the "unmodified" TM.
>
>OK, suppose you're in a set of identical computational histories that are
>unfolding on many different TMs. Some of those histories are about to go
>strange. For your existence as an observer to continue, they must go
>strange
>in such a way that they still support you as an observer. Given what I have
>said, do you think you are likely to branch into a strange world or to
>continue on in your normal world, whatever that may be? The measure of the
>computational history of the world where you continue on as normal is much
>larger than the measure of the computational history of the strange branch
>because the strange TMs receive less runtime (remember, many different TMs
>instantiate you).
>
>So, if you were an observer on the dovetailer, your computational history
>branches in such a way that some branches are much more probable than
>others. The world the observer observes will likely not be totally stupid.
>
>This is how you play into Bruno's hands!
>
>Writing the above has made me realize that I may have not been accurate in
>some of my earlier statements about Bruno's work. Apologies to Bruno. All I
>need now is to be convinced that we can give a satisfactory definition of
>an
>observer. Oh, and that we are most likely to observe QM.
>
>Brian Scurfield
>
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Received on Fri May 06 2005 - 11:48:15 PDT