Bruno asked a while back for various people to try to encapsulate
their favorite theory or model of the "everything exists" concept,
so I will try to describe my current views here.
Basically it can be summed up very simply as: Universal Distribution
(UD) plus ASSA (absolute self selection assumption).
Traditional philosophy distinguished between ontology, the study of the
nature of reality, and epistemology, which examines our relation to and
understanding of the world. I can adopt this distinction and say that
the UD is the ontology, and that the epistemology is roughly the ASSA.
As you will see, my ontology is stronger than my epistemology.
[Note, UD is often used to mean Universal Dovetailer, a different
concept.]
For the ontology, the UD is a probability distribution over information
objects (i.e. information patterns) which I assume is the fundamental
system of measure in the multiverse. It is defined with respect to an
arbitrary Universal Turing Machine (UTM) and basically is defined as
the fraction of all possible input program strings that produce that
information pattern as output.
I am therefore implicitly assuming that only information objects exist.
Among the information objects are integers, universes, computer programs,
program traces (records of executions), observers, and observer-moments.
The UD is an attractive choice because it is "dominant", meaning that it
is asymptotically within a constant factor of any other distribution,
including UD's defined by other UTMs. This is why it is called
"universal". It is often considered the default probability distribution
when no information is available. This makes it a natural choice, perhaps
the only natural choice, for a distribution over information objects.
The UD defines a probability or "measure" for every information object.
This is the basic ontology which I assume exists. It is the beginning
and ending of my ontology.
A few additional points are worth making. Time does not play a
significant role in this model. An information object may or may not
include a time element. Time is merely a type of relationship which
can exist among the parts of the information object, just as space is
another type. In relativity theory, time is different from space in
the sign (positive/negative) by which its effects are made known on the
metric.
Among universes, some may have a time dimension, some may not; some
may have more than one dimension of time. Similarly, they could have
different dimensions of space, or perhaps fractal dimensions.
Observers are by definition information systems that are similar to us,
and since time is intimately bound up in our perception of the world,
observers will be information objects which do include a time element.
It is also worth noting that the UD measure is non-computable. However
it can in practice be approximated, and that seems good enough for my
purposes.
Another point relates to the question of copies. One way to interpret
the UD is to imagine infinite numbers of UTMs operating on all possible
programs. The measure of an object is the fraction of the UTMs which
output that object. This inherently requires that "copies count", even
exact copies. The more copies of an information object are created, the
more measure it has.
A final point: I strongly suspect that the biggest contribution to the
measure of observers (and observer-moments) like our own will arise from
programs which conceptually have two parts. The first part creates a
universe similar to the one we see where the observers evolve, and the
second part selects the observer for output. I argued before that each
part can be relatively small compared to a program which was hard-wired
to produce a specific observer and had all the information necessary to
do so. Small programs have greater measure (occupy a greater fraction
of possible input strings) hence this would be the main source of measure
for observers like us.
For the epistemology, we need some way to relate this definition of
measure to our experience of the world. This is necessary to give the
theory grounding and enable it to make predictions and explanations.
What we want is to be able to explain things by arguing that they
correspond to high-measure information patterns. We also want to be
able to make predictions by saying that higher measure outcomes are
more likely than lower measure ones. To achieve this I want to adopt
a relatively vague statement like:
You are more likely to be a high measure information object.
Obviously this statement raises many questions. It seems to suggest
that you might be a table, or the number 3. It also has problems
with the passage of time. "When" are you a given information object?
Are you first one and then another? If you start off as one, do you
stay the same?
I am not necessarily prepared to fully explain and answer all of these
problems. At this point I am trying to keep to the big picture. Objects
have measure, and for that to be meaningful, objects with higher measure
have to be considered more prominent. We should expect the universe
we observe to have relatively high measure. We should expect ourselves
as observers, and as observer moments, to have relatively high measure.
If we face alternatives of either a low measure or a high measure future,
we should expect to experience the high measure one.
As far as the problem of "being" unconscious objects, I don't necessarily
see that as contradictory. We all know what it is like to be unconscious.
We become unconscious every day when we sleep. We also know through
experience that there are many degrees and kinds of consciousness.
In practice, being a table or the number 3 is so different from what we
think of as consciousness that we cannot relate to it as human beings.
We need to restrict our attention to information objects that have a
similar nature and complexity to our own. Among those objects, we can
distinguish between ones with low and high measure. The theory predicts
that we should find ourselves as entities with a relatively high measure,
and explains those aspects of our existence which have a high measure.
The ASSA is well suited for this interpretation, because it relates
measure of observer moments to subjective probability. The older SSA,
which is observer based where the ASSA is observer-moment based, also
can work reasonably well in this model for the same reason.
But the details of ASSA vs ASA vs other interpretations are not of
fundamental importance in my view. The most important part is the UD.
We then connect its definition of measure to subjective experience using
the concept that higher measure states are more likely to be experienced.
This is the basic principle from which we attempt to make our predictions
and explanations.
Hal Finney
Received on Sun Jul 10 2005 - 23:51:28 PDT
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