Chris Menzel wrote:
Who said anything about exact
representation? My claim is only that models/theories can get the world
right as far as they go.
That
would run into quantum mechanical effects, and an
impossibly large amount of data. Approximations are the norm.
As engineers say, "All models are wrong, but some are useful."
It's a stupid slogan. Models are useful (typically) because they
get the world right to some extent, at some level of granularity.
If that weren'tt so, their usefulness would be a complete mystery.
John's earlier point was that a model gets some aspect of the
world right. That, as Chris says, is what makes it useful. I think the
problem is that 'approximation' is a poor word for the relationship of
the model to the thing/world. The model accurately renders some
subset of the properties of the thing/world.
I am, however, reminded of a colleague's long-standing email tag
quotation:
"A theory has only the alternative of being right or wrong. A
model has a third possibility: it may be right but irrelevant."
-- Manfred Eigen
But that really says only that a model has a purpose. The subset of
properties of the thing/world that it captures must be the "right"
subset for that purpose, and any other subset is useless for the
purpose. Deming's "all models are wrong" simply admits that a model
intentionally misrenders aspects not relevant to the purpose. And a
formal logic "model" simply omits them.
-Ed
--
Edward J. Barkmeyer Email: edbark@xxxxxxxx
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263 Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263 Cel: +1 240-672-5800
"The opinions expressed above do not reflect consensus of NIST,
and have not been reviewed by any Government authority."
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