Re: Theory, Model and Law

From: Ilja Schmelzer (Ilja.Schmelzer_at_FernUni-Hagen.de)
Date: 10/27/04 

Date: Wed, 27 Oct 2004 15:59:53 +0000 (UTC)

"Arnold Neumaier" <Arnold.Neumaier@univie.ac.at> schrieb
> news user wrote:
> > In article <4154417C.2060504@univie.ac.at>, Arnold.Neumaier@univie.ac.at
> > says...
> >>A correct theory cannot be falsifiable, in spite of Popper.

??????? A correct theory is not false and therefore will not
be actually falsified. But, if the Sun falls down and appears to be
a large light bulb some of the standard theories appear to be falsified.

> > I was under the impression that it does. For example,
> > the Standard Model claims to be valid whenever gravitation
> > is negligeable, isn't-it ?
>
> Yes, and when, in addition, energies are well below a putative
> unification scale. Failures outside this domain are not
> counted as falsifications.

That does not make the theory unfalsifiable.

> In today's understanding, people are careful to indicate the
> limits where a theory is claimed to be valid, and the accuracy
> to which its answers are to be trusted. While this is not part
> of the theory proper, it is part of the theory as actually taught
> and applied. Indeed, although people try to extrapolate, one can
> never be sure whether a theory is correct outside the domain where
> the data were collected.

Extrapolation for tomorrow is also extrapolation, so you can never
be completely sure.

> But one can be reasonably sure within the domain where enough data
> are available.

Of course. But this is not the point of Popper's theory.

> Once this is the case, these theories can never be
> falsified. Rather, if people find disagreement in experiments, the
> theory falsifies the experimental arrangement or analysis.
> All science students who ever did experiments in the lab know
> very well that this is common practice.

Of course, if an experiment is in disagreement with theory in a
well-tested domain, it is usually the experimental arrangement or
the analysis which are wrong. But this does not mean that the
theory is unfalsifiable.

> Certainly Newton's theory as taught today is
> taught with the restriction that it is valid at speeds small compared to
> c and at distances large compared to the radius of the largest atom.
> But we nevertheless believe that it is the 'same' theory, and if
> Newton would live today, I think he would agree with that.

That's simply economy of words in common language. Instead of
"Newtonian theory original version"
"Newtonian theory as SR-limit version"
"Newtonian theory as GR-limit version"
"Newtonian theory as classical limit of Schroedinger theory version"
we use simply "Newtonian theory".

Ilja