  We will display the fundamental structure of classical electrodynamics.
Starting from the axioms of (1) electric charge conservation, (2) the existence
of a Lorentz force density, and (3) magnetic flux conservation, we will derive
Maxwell's equations. They are expressed in terms of the field strengths
$(E,{\cal B})$, the excitations $({\cal D},H)$, and the sources $(\rho,j)$.
This fundamental set of four microphysical equations has to be supplemented by
somewhat less general constitutive assumptions in order to make it a fully
determined system with a well-posed initial value problem. It is only at this
stage that a distance concept (metric) is required for space-time. We will
discuss one set of possible constitutive assumptions, namely ${\cal D}\sim E$
and $H\sim {\cal B}$. {\em file erik8a.tex, 1999-07-27}
