To believe that you need
something more complex, you need evidence.
Yes, and the evidence that you need something more complex is overwhelming
in this case (if you have anywhere near adequate knowledge of the field).
----- Original Message -----
From: "Vladimir Nesov" <[EMAIL PROTECTED]>
To: <agi@v2.listbox.com>
Sent: Monday, June 02, 2008 2:59 PM
Subject: Re: [agi] Ideological Interactions Need to be Studied
On Mon, Jun 2, 2008 at 8:37 PM, Richard Loosemore <[EMAIL PROTECTED]>
wrote:
This misses the point I think.
It all has to do with the mistake of *imposing* simplicity on something
by
making a black-box model of it.
For example, the Ptolemy model of planetary motion imposed a 'simple'
model
of the solar system in which everything could be explained by a set of
nested epicycles. There would have been no need to use any other model
because in principle those epicycles could have been augmented to
infinite
depth, to yield as good a fit to the data as you wanted.
That is a black-box model of the solar system because it stuffs all the
real
complexity inside a black box and then models the black box with a
simplistic formalism. If all you care about is getting a precise model
of
planetary movement across the sky, this would be (and was!) the simplest
model anyone could ask for.
But it was wrong. It was wrong because it obscured the real situation.
The
real situation could not be understood without inventing a whole new type
of
mathematics (calculus) and discovering a new law of nature (universal
gravitation). By any measure, that combination of calculus and
gravitation
was a more "complicated" explanation.
Anyone at the time who knew that Isaac Newton was trying to do could have
dismissed his efforts and said "Idiot! Planetary motion is simple.
Ptolemy
explained it in a simple way. I use simplicity-preferring prior, so
epicycles are good enough for me."
And if that same person insisted that there SHOULD be a simple model of
planetary motion (where "simple" meant 'as simple as epicycles") would
have
been insisting that an explanation as complicated as calculus and
gravitation was in some sense bad or unparsimonious.
In the long run, of course, gravity plus calculus was perceived as being
'simple' and elegant in the extreme. But that is not the point, because
before it was discovered it could have been criticised as being far, far
more complicated than the epicycle explanation.
I could argue that your example is a strawman, but it's not a very
relevant issue. My point is that you have to have some prior, and
prior that prefers simplicity is as good as any (or better, by
exploiting implicit statistics-gathering during notation-building). If
you do have some additional information that says that this particular
distribution is not good enough, it should be updated. Probability
expresses incompleteness of knowledge. To believe that you need
something more complex, you need evidence.
--
Vladimir Nesov
[EMAIL PROTECTED]
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