  A dynamical model for varying light velocity in cosmology is developed, based
on the idea that there are two metrics in spacetime. One metric $g_{\mu\nu}$
describes the standard gravitational vacuum, and the other ${\hat g}_{\mu\nu}
=g_{\mu\nu}+\beta\psi_\mu\psi_\nu$ describes the geometry through which matter
fields propagate. Matter propagating causally with respect to
$\hat{g}_{\mu\nu}$ can provide acausal contributions to the matter
stress-energy tensor in the field equations for $g_{\mu\nu}$, which, as we
explicitly demonstrate with perfect fluid and scalar field matter models,
provides a mechanism for the solution of the horizon, flatness and magnetic
monopole problems in an FRW universe. The field equations also provide a
``graceful exit'' to the inflationary epoch since below an energy scale
(related to the mass of $\psi_\mu$) we recover exactly the standard FRW field
equations.
