On Fri, Jul 9, 2010 at 11:37 AM, Ben Goertzel <[email protected]> wrote:

>
> I don't think Solomonoff induction is a particularly useful direction for
> AI, I was just taking issue with the statement made that it is not capable
> of correct prediction given adequate resources...


Pi is not computable.  It would take infinite resources to compute it.
However, because Pi approaches a limit, the theory of limits can be used to
show that it can be refined to any limit that is possible and since it
consistently approaches a limit it can be used in general theorems that can
be proven through induction.  You can use *computed values* of pi in a
general theorem as long as you can show that the usage is valid by using the
theory of limits.

I think I figured out a way, given infinite resources, to write a program
that could "compute" Solomonoff Induction.  However, since it cannot be
shown (or at least I don't know anyone who has ever shown) that the
probabilities approaches some value (or values) as a limit (or limits), this
program (or a variation on this kind of program) could not be used to show
that it can be:
1. computed to any specified degree of precision within some finite number
of steps.
2. proven through the use of mathematical induction.

The proof is based on the diagonal argument of Cantor, but it might be
considered as variation of Cantor's diagonal argument.  There can be no one
to one *mapping of the computation to an usage* as the computation
approaches infinity to make the values approach some limit of precision. For
any computed values there is always a *possibility* (this is different than
Cantor) that there are an infinite number of more precise values (of the
probability of a string (primary sample space or compound sample space))
within any two iterations of the computational program (formula).

So even though I cannot disprove what Solomonoff Induction might be given
infinite resources, if this superficial analysis is right, without a way to
compute the values so that they tend toward a limit for each of the
probabilities needed, it is not a usable mathematical theorem.

What uncomputable means is that any statement (most statements) drawn from
it are matters of mathematical conjecture or opinion.  It's like opinioning
that the Godel sentence, given infinite resources, is decidable.

I don't think the question of whether it is valid for infinite resources or
not can be answered mathematically for the time being.  And conclusions
drawn from uncomputable results have to be considered dubious.

However, it certainly leads to other questions which I think are more
interesting and more useful.

What is needed to promote greater insight about the problem of conditional
probabilities in complicated situations where the probability emitters
and the elementary sample space may be obscured by the use of complicated
interactions and a preliminary focus on compound sample spaces?  Are there
theories, which like asking questions about the givens in a problem, that
could lead toward a greater detection of the relation between the givens and
the primary probability emitters and the primary sample space?

Can a mathematical theory be based solely on abstract principles even though
it is impossible to evaluate the use of those abstractions with examples
from the particulars (of the abstractions)?  How could those abstract
principles be reliably defined so that they aren't too simplistic?

Jim Bromer



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