  This paper gives an introduction to certain classical physical theories
described in the context of locally Minkowskian causal structures (LMCSs). For
simplicity of exposition we consider LMCSs which have locally Euclidean
topology (i.e. are manifolds) and hence are M\"{o}bius structures. We describe
natural principal bundle structures associated with M\"{o}bius structures.
Fermion fields are associated with sections of vector bundles associated with
the principal bundles while interaction fields (bosons) are associated with
endomorphisms of the space of fermion fields. Classical quantum field theory
(the Dirac equation and Maxwell's equations) is obtained by considering
representations of the structure group $K\subset U(2,2)$ of a principal bundle
associated with a given M\"{o}bius structure where $K$, while being a subset of
$U(2,2)$, is also isomorphic to $SL(2,{\bf C})\times U(1)$. The analysis
requires the use of an intertwining operator between the action of $K$ on ${\bf
R}^4$ and the adjoint action action of $K$ on $u(2,2)$ and it is shown that the
Feynman slash operator, in the chiral representation for the Dirac gamma
matrices, has this intertwining property.
