"James Higgo" wrote:
>Jesse,
>
>The point you picked up 'self-referential thought' is not relevant to the
>discussion we were having. However, it is the most interesting thing in my
>post.
I think it's actually pretty relevant. What we're talking about is what
Nick Bostrom calls "the problem of the reference class" in
anthropic/copernican reasoning (although this problem only crops up in
certain versions of anthropic reasoning; see below). Part of my argument
for a theory of consciousness is that I don't think there's a good way to
deal with this except by referring to conscious observer-moments. You seem
to be saying that we can deal with it in terms of "self-referential
thoughts" or something similar...but you may actually be using a version of
the anthropic principle where the reference-class problem doesn't come up in
the first place (again, see below).
>I have been thinking about this for a while. The only thoughts that we can
>apply the anthropic principle to are thoughts about the anthropic
>principle.
>
>The only thing we know to exist is a thought about why we exist. So the
>number of possible universes is restricted to those in which thoughts about
>why we exist can be supported.
>
>The universe need not contain thinkers, far less 'human beings' with
>brains,
>blood and other thoughts. The anthropic principle is universally
>mis-applied
>by everyone who has ever written on he subject because they make the leap
>from their thought to a thinker. This leap, as I have long argued, is
>unjustifiable.
I think we need to distinguish between two kinds of anthropic reasoning
here. The first version just says "I observe that I exist, so I know with
probability 1 that I must occupy a time and place where my existence is
possible." Obviously this is completely uncontroversial. In this version,
though, it's not really important that you say "I exist" or "intelligent
observers capable of anthropic reasoning exist"--you could just as easily
have made up the "star-thropic principle" which says that you know with
probability 1 that stars exist, so you must be in a time and place where
star formation is possible.
As originally envisioned by Carter, both the "strong" and "weak" anthropic
principles were versions of this idea. In "Modern Cosmology & Philosophy,"
John Leslie writes that "Carter's weak principle reminds us of the obvious
but oft neglected truth that our place and time must, granted that we are in
fact there, be a place and time where observers can exist: they are not, for
example, fried immediately, as they would be shortly after the Big Bang.
Carter's strong principle similarly reminds us that our universe must--as we
do exist in it, don't we?--be a universe whose nature is not
life-excluding...the 'must' is in both cases like that of 'The photo is
marked WIFE, so *must* be of a woman.' No suggestion that the photo *had to
be* of a woman or that it is somehow especially easy to be a woman!"
But there's another version of "anthropic reasoning" which, although it
perhaps deserves a different name, seems to me to be valid as well. This
version says that, given that at least some observer-containing regions
exist, "I" must find myself in one of these regions. In this case "I" is
like the "I" in the Doomsday argument, which says "I" could have been born
at any time in history, despite the fact that I wouldn't be the same person
if I'd been born at some other time. In this version the fact that we're
talking about "observers" is important--it wouldn't work with stars or
anything else.
If I win the lottery, I'm pretty "lucky"--I could just as easily have been
one of the losers. On the other hand, despite the fact that physically
realized genetic codes occupy only a tiny fraction of the space of all
possible human DNA sequences, I wouldn't say I'm "lucky" to have an existing
sequence rather than a nonexisting one--it isn't possible to "be" a
nonexistent person, so of course I'm one of the existing ones (assuming for
the moment that these other sequences aren't realized in a parallel universe
or something). This is an application of the second version of anthropic
reasoning.
The distinction between these two versions still may not be entirely clear.
Another way to put it is that the second version, when coupled with the
assumption of multiple universes/regions, allows you to *explain* why you
find yourself in what is possibly a quite unlikely set of circumstances.
For instance, if we assume that many physical constants are indeed set
randomly, then it seems the fact that our universe's constants are
fine-tuned to allow life becomes less puzzling if we assume multiple
universes (or multiple regions with different constants). In this case, the
"explanation" for the apparent fine-tuning is that at least one
correctly-tuned universe is likely to exist, and the second version of the
anthropic principle says that's the universe that "I" must find myself in.
In contrast, the first version can't explain anything at all--it's just a
statement about your prior knowledge.
An even clearer way to distinguish the two versions is that the second
version allows you to make new inferences about reality, while the first
only describes what you already know. For example, if we find that our
universe is indeed fine-tuned, then by a version of Bayesian reasoning we
can say we should be more inclined to believe in the existence of other
universes with different constants, in order to explain the "coincidence" of
observed fine-tuning (to make this more obvious, feel free to assume we know
a priori that there's a 50% chance God created a single universe and a 50%
chance he created a multiverse).
This is similar to "copernican" reasoning, like the Doomsday argument, which
also allows you to infer new things about reality just by observing your own
position in it. In fact, I'd make a case for distinguishing the two
anthropic principles by saying the second is identical to what's sometimes
called the "copernican anthropic principle." For example, most people who
say fine-tuning increases the probability of multiple universes would also
say that we're more likely to find ourselves in a universe where observers
(or observer-moments) are more common rather than one where they are rare,
assuming the number of each kind of universe is about equal.
So my question for you is, when you say "the anthropic principle is
universally mis-applied," are you saying that you think only Carter's
original version of anthropic reasoning is valid, while the copernican
anthropic principle is not? Or do you accept the copernican anthropic
principle but think the "reference class" can only consist of
observer-moments that are using anthropic reasoning? Or something else?
>You ask: "Is it just amazing luck that I find myself to be one of these
>extremely rare complex observer-moments?" - surely you don't mean this.
>That
>is equivaent to the traditional question "Is it amazing luck that the
>universe supports my life", to which the traditional mis-application of the
>anthropic principle is the ripost.
This ripost only works if you assume multiple universes/regions, although I
suppose you might say it doesn't work even then.
>Obviously, if you were not one of these rare complex observer moments you
>would not be asking why you were one. Luck has nothing to do with it. It is
>a 100% certainty.
You misunderstood my point. I was saying that if my "reference class"
includes all "self-referential thoughts", and if my definition of
self-referential thoughts is such that simple ones greatly outnumber complex
ones, then I can *not* use anthropic reasoning (of either sort) to explain
why I find myself to be a rare complex one rather than a simple one...so the
fact that I am a complex one would be very, very lucky in this case. This
then becomes a reason to say the original choice of reference class may have
been incorrect.
And this is still true if you replace "self-referential thought" with
"thought about the anthropic principle" or something similar. I can write a
simple program that prints out "I am thinking about the anthropic
principle", and the number of physical systems that implement this program
is probably still much greater than the number of systems that implement the
complex processes going on in my brain (unless you take Hans Moravec's view,
in which any system can be seen as implementing any 'thought' under the
right mapping).
>As an aside, these observer moments are not rare, in that there is an
>infnite number of them. Jacques Mallah might argue, however, that they have
>low measure in the universe of thoughts. Having said that, viz the CD that
>maps all natural numbers onto a series of thoughts, you need some external
>mapping system to decide what is a thought and what isn't. From some
>perspective, from some mapping, all series in the universe can be viewed as
>a self-referential thought.
So you do take Hans Moravec's view? But in that case, why do you think that
observer-moments of the laws of physics operating normally should be any
more common than observer-moments seeing crazy violations of physical law?
If any physical system can map onto any kind of observer-moment I don't see
how this can be explained.
>[Note: I use the terms 'thought' and'observer moment' interchangeably:
>'observer moment' is the orthodoxy of this list, but I prefer 'thought'
>since it does not imply an observer. This is still a bit sloppy but I guess
>the terminology wil firm up in due course.]
Would a program that prints out "I am thinking about the anthropic
principle" count as a "thought" about the anthropic principle? If not, on
what basis do you rule it out?
Jesse Mazer
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Received on Mon Feb 12 2001 - 08:21:27 PST