On 9/24/2011 7:20 PM, Pierz wrote:
OK, so I've read the UDA and I 'get' it, but at the moment I simply
can't accept that it is anything like a 'proof'. I keep reading Bruno
making statements like "If we are machine-emulable, then physics is
necessarily reducible to number psychology", but to me there remain
serious flaws, not in the logic per se, but in the assumptions.
Bruno says that "no science fiction devices are necessary, other than
the robust physical universe". He also claims that to argue that the
universe may not be large or robust enough (by robust I assume he
means stable over time) to support his Universal Dovetailer is "ad
hoc and disgraceful". I think it is anything but. To describe such an
argument as "disgraceful" is to dismiss with a wave of the hand the
entirety of modern cosmology and physics, disciplines which after all
have managed to produce a great deal more results in the way of
prediction, explanation and tangible benefits than Bruno's theory (I
insist it is a theory and not a 'result'). As a computer science
expert, I assume Bruno is aware of modern computational approaches to
physics. Such approaches explicitly forbid any kind of 'infinite
informational resolution' as is required by Bruno's theory. The
information content of the universe is seen as being a fundamental
quantity much like energy, constantly transforming but conserved over
the whole system in the same way energy is. This computational
approach indeed seems to be the *basis* for much of Bruno talks about
(computability, emulability and so on are all fundamental ideas), but
then he flies in the face of it by proposing some kind of automated,
Platonic computation devoid of any constraints in terms of state
memory or time.
Let's take a look at the UD. Obviously this is not an 'intelligent'
device, beyond the intelligence implicit in the very simple base
algorithm. It just runs every possible computer program. Random
computer programs are made of and produce *static*, they are a random
arrangement of bits. Now clearly, we know that if you look at a large
enough field of static, you will find pictures in it, assemblies of
dots that happen to form structured, intelligible images. Likewise in
the field of random computed algorithms, very very occasionally one
will make some kind of 'sense', although the sense will naturally be
entirely accidental and in the vast, vast majority of cases will give
way a moment later to nonsense again. So when the UD runs through its
current sequence of programs, what it is really doing is just
generating a vast random field of bits. Nonetheless, each of these
individual programs needs to have potentially infinite state memory
available to it (the Turing machine tape). Now the list of of programs
run by the machine continues to grow with each iteration as it adds
new algorithms, so it takes longer and longer to return to program 0
to run the next operation. As it needs to run *all* programs, a
necessarily infinite number, it requires infinite time, but for some
reason Bruno thinks this is not important. Either it has infinite
processing speed as well as memory, or it has infinite time on its
hands.
If you are simulating a physical process on a computer, the time the computer takes to
simulate one second of the physical process may be anything. The simulator time and the
simulated time are completely different. The simulated events need not even be produced
in the order of their (simulated) time stamp.
Fine. But then we can simply dispense with the UD altogether and just
gather up its final results,
It has no final results since in general the programs will not terminate.
which is an infinite field of static, a
giant digital manuscript typed by infinite monkeys. Everything capable
of being represented by information will exist in this field, which
means it is capable of "explaining" everything. And nothing.
I empathize with that objection. It is easy to produce everything, but what we want is an
explanation for *this* thing. This is known as "the white rabbit problem" or the "measure
problem" since implicitly the idea to explain that there is some natural measure by which
*this* is highly probable and *that*, including Alice's white rabbit, is highly
improbable. The whole problem is pushed off into finding and justifying this measure.
We have to deconstruct the notion of "computation" here. Computation
is the orderly transformation of information. But the UD's orderliness
is the orderliness of the typing monkey. If it is orderly at all, it
is by mistake. By talking about it the UD as performing computation
more intelligence is implicitly imputed than this hypothetical device
possesses. Yes, it would generate every possible information state,
and would therefore create me and all my possible futures, but these
'pictures' would have no coherence, would immediately dissolve back
into the static they emerged from. The UD, as a generator of static,
cannot explain coherence in my experience.
There is a fundamental circularity here. Something must explain the
coherence of 1p and 3p accounts (laws of physics). Because the UD must
exist (someone please explain this to me!), the explanation must lie
in the UD. Because the UD is pure computation, the laws of physics
(the coherence) must be reducible to principles of computation. But
why no earth must the UD exist? And if it did exist, the reduction of
the UD to an infinite static field shows that it is devoid of such
explanatory power. Only if there is something about the UDA that
confines it to meaningful, orderly algorithms (whatever that might
mean), can Bruno's argument follow. But the UD's algorithm is a few
lines of code, there is no hidden magic to allow it to select such
algorithms. We have to throw out the UD, not the laws of physics.
The whole notion of the 'teleporting consciousness' is obviously
fundamental to the argument. It is assumed by 'yes doctor' (and argued
for in step 8) that consciousness is not bound to any physical
substrate, but is a function of certain computational states - ie
arrangements of bits. What again is deeply unclear is how a boundary
is formed around such arrangements to give them coherence in the
overall field. In an infinite field of transforming information - the
output of the UD - there will be areas of apparent coherence, but the
coherence is apparent, not real. Such a coherent region could only be
identified by a mind (or computer) capable of recognizing coherence or
pattern. The UD does not possess such intelligence,
It would not be appropriate to invoke intelligence in the explanation, since part of the
point is to explain intelligence, consciousness, etc. After all there is no assumption
that the equations of physics are "intelligent"; yet they provide a pretty good story of
the origin and development of the universe.
or only as yet
another algorithm which is on the same level as the other algorithms,
and not capable of accessing the states of all other computational
threads. You'd need to posit some new level of meta-computation
picking out the coherent results of the UD from the incoherent ones,
but how does *it* recognise coherence? It's an infinite regress.
"It" doesn't. It is rather that coherence picks out "us". But this is rather like the
Boltzman brain problem. For example if it picks out me according as some measure makes
"me" more probable, why don't I find myself in a world in which everyone is Brent Meeker.
Brent
"A theory that can explain anything, fails to explain at all."
And how do these coherent areas of the field which we call
consciousnesses (or 1p) connect with their self-similar regions in the
UD output? There may be pictures of me in all possible states within
this field, but they will be completely disconnected from one another.
How does the consciousness apparently implicit in the picture of me
'join the dots' between these random images to make a timeline which
defines my history? The argument that it is 'machine psychology' or
'laws of arithmetic' merely begs the question - or obfuscates it.
In the end, the UDA merely asserts the results of its own assumptions,
but the assumptions are profoundly doubtful. You can dress the
emperor's nakedness up in a lot of fancy mathematical formulism and
obscure verbal manoeuvres, but he is still naked. Infinite randomness
is a 'powerful' explanation because you can find anything you like
inside it. But when you see how vast the sea of surrounding
meaninglessness is, you realise the bankruptcy of that mode of
explanation.
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