  We present a classical linear response theory for a magneto-dielectric
material and determine the polariton dispersion relations. The electromagnetic
field fluctuation spectra are obtained and polariton sum rules for their
optical parameters are presented. The electromagnetic field for systems with
multiple polariton branches is quantised in 3 dimensions and field operators
are converted to 1-dimensional forms appropriate for parallel light beams. We
show that the field-operator commutation relations agree with previous
calculations that ignored polariton effects. The Abraham (kinetic) and
Minkowski (canonical) momentum operators are introduced and their corresponding
single-photon momenta are identified. The commutation relations of these and of
their angular analogues support the identification, in particular, of the
Minkowski momentum with the canonical momentum of the light. We exploit the
Heaviside-Larmor symmetry of Maxwell's equations to obtain, very directly, the
Einsetin-Laub force density for action on a magneto-dielectric. The surface and
bulk contributions to the radiation pressure are calculated for the passage of
an optical pulse into a semi-infinite sample.
