On 3/10/2018 3:17 PM, Bruce Kellett wrote:
From: *Russell Standish* <li...@hpcoders.com.au
<mailto:li...@hpcoders.com.au>>
On Fri, Mar 09, 2018 at 08:23:40PM -0800, Brent Meeker wrote:
> > momentum produced from it unless there was a symmetry, in this case
> > the fact that the laws of physics are the same at all points in
space.
> > Someone could then ask why that is, and at this time the best
answer we
> > could give is that’s just what we observe. As far as I can see it
is not
> > a logical necessity, physics could have been different from one
place to
> > another but we see that is not the case.
> >
>
> If that were the case then we would look for some other variable(s)
that
> would account for the difference in order to arrive at a more
comprehensive
> theory that, with the new variable(s), made the theory the same both
> places. The idea of physics as a fundamental theory is that it
should be
> the same at all times and places. So if it's not, we either look for a
> better theory or (temporarily) give up and call the variations
"geography".
> As my friend Vic Stenger put it, physics assumes POVI, Point Of View
> Invariance.
>
> Brent
Exactly - POVI is a choice, not a necessity. It makes the theories
simpler.
I don't really like the idea that POVI is just a choice to make our
theories simpler. That implies that symmetries are our choice and nor
something inherent in the physical world. The consequence would be
that our theories tell us only about our preferred way of looking at
things, and not anything about 'reality'. While consistent with an
instrumentalist perspective, that means that we have given up on
learning anything about the objective world. A more generous view of
instrumentalism does not require that our theories tell us nothing
about the external world.
My feeling is that we observe that the world has certain symmetries,
then we design our theories to reflect these symmetries, because
theories that incorporate the observed symmetries work better. Since
the starting point is observation, we have some prospect of learning
something other than the nature of our thought processes.
We want POVI. We look for symmetries, which are no more than patterns,
that we can build theories around. The fact that we're only satisfied
with theories that don't depend on particularities, i.e. are as general
as possible, doesn't mean we can make them out of whole cloth,
independent of observation.
Brent
Bruce
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