[From Bruce Gregory (960821.1525 EDT)]
(Martin Taylor 960821 14:10)
Now, Occam's razor deals in marginal rates, at least as I see it. Once one
has invested in a model that provides good returns, and no further investment
is required (i.e. no further assumptions or ad-hoc data) for it to account
for new data, the Occam's cost of using that model is zero. To discard that
model and use a new one that is seen as simpler by someone else (it cannot
be simpler on any _absolute_ scale) is to make a new investment. The cost
is considerable, and can be justified only if the new model provides
greater precision or a wider range of circumstances for which predictions
are made. It has to cover what the old model already did cover.
I agree.
Me:
Further, MCT requires all the machinery of PCT.
You:
That is false, as I understand MCT. PCT has a considerable machinery of
hierarchic linkages and perceptual functions, and these do not occur in
MCT. The explicit model takes their place.
Thanks for the clarification.
Me:
>If PCT gets the job done, there is no _need_ to invoke MCT,
You:
True. And if MCT gets the job done, there is no _need_ to invoke PCT. The
question is: can a situation be described in which either one of PCT and
MCT gets the job done whereas the other does not? So far, I have seen no
valid proposals for such a situation.
Agreed, although Rick has been trying to get Hans to identify
one.
What does Occam's razor say to the PCT-only position if a situation can be
found in which MCT "gets the job done" easily, but PCT does only with complex
extra assumptions? Or vice-versa?
I think the general principle which is a least on the same level
as Occam's razor is that ad hoc assumptions are to be avoided.
Whichever theory "gets the job done easily" is to be preferred.
It's all perception, and we have no other access to the "real" world. If
there is anything in the "real" world that we can call "absolute simplicity,"
how would you know if you were correctly perceiving it?
I agree. Unless the theories make different predictions,
preferences are aesthetic rather than scientific.
Regards,
Bruce