[Phys-L] Re: Energy is primary and fundamental?

[jsd at AV8N.COM (John Denker)]

Rauber, Joel wrote:

> It strikes me that this criticism borders on being a criticism of the
> correspondence principle, so I don't find it quite so bothersome.

Surely none of us objects to the correspondence principle per se.  My
point was that the correspondence principle is a one-way street, and it
is important to get the directionality right:  an older, less-general
result emerges from the newer, more-general result in the correspondence
limit ... and not vice versa.

In the present case, classical results such as F=ma emerge from
the Lagrangian in the appropriate limit ... and not vice versa.
A more familiar example of the same process is geometric optics,
which emerges from physical optics in the appropriate limit, i.e.
when all the interference terms wash out.