Re: What are "principles" in science?

[Mark Sylvester <msylvest@XNET.IT>]

At 09:32 08/06/04 -0400, Robert Cohen wrote:
> On Tuesday, June 08, 2004 4:04 AM, Mark Sylvester wrote:
>
> > Otoh Boyle's Law is easily characterized as an empirical law,
> > and "Newton's Laws", together with the "Law of Gravity"
> > constitute a theory in the proper sense, "explaining" as they
> > do, amongst many other  things, Kepler's Laws, which are
> > again empirical laws, being a (mathematical) generalization
> > from observation.
>
> This may be splitting hairs but I disagree about Newton's laws
> and the "law of gravity".  Although they can be used to
> "explain" other relationships, that does not transition them
> from "laws" to "theories".  They do not "explain" in the same
> sense that the atomic theory explains the properties of
> materials.  I know this sounds ambiguous.  Simply put --
> the law of gravity doesn't explain why there is gravity; it
> only states that the gravitational force is related to mass
> and distance.

I admit that this is a tricky case, but I come down on the "theory" side
for Newton for the following reasons:

1. Newton redefines our understanding of mass and force and their relation
to motion. There is something here not "observable" a priori. Only once we
committed to the Newtonian paradigm is it all obvious. F proportional to
dp/dt is a different kind of statement from P proportional to 1/V. Whatever
Newton was doing, he was surely not proceeding by induction from a number
of observations.
2. The Law of Gravity requires us to believe that there is this force.
True, we feel something making things fall, but that's the only example,
and we already have intuitions about it. The Cavendish balance comes later.
Requiring acceptance of something not directly observable is characteristic
of a theory.
3. The payback for accepting the paradigm is huge. Not only do we now
understand where Kepler's Laws come from, but we can predict correctly the
existence of new planets from small deviations. And a few other things as
well. The fruitful nature of this small number of statements is again
typical of a theory.

True, Newton doesn't enable us to understand what gravity is,
but  historical context is not irrelevant. Atomic theory doesn't enable us
to understand why there are atoms.

Mark

Mark Sylvester
UWCAd
Duino Trieste Italy