  The role of the vacuum, in the Casimir Effect, is a matter of some dispute:
the Casimir force has been variously described as a phenomenon resulting "from
the alteration, by the boundaries, of the zero-point electromagnetic energy",
or a "Van der Waals force between the metal plates" that can be "computed
without reference to zero point energies". Neither of these descriptions are
grounded in a consistently quantum mechanical treatment of matter interacting
with the electromagnetic field. However, the Casimir Effect has been
canonically described within the framework of macroscopic quantum
electrodynamics. On this account, the force is seen to arise due to the
coupling of fluctuating currents to the zero-point radiation, and it is in this
restricted sense that the phenomenon requires the existence of zero-point
fields. The conflicting descriptions of the Casimir Effect, on the other hand,
appear to arise from inadequate ontologies in which an unwarranted metaphysical
priority is assigned either to the matter or the fields. Such ontological
errors may have a direct bearing on the problem of the cosmological constant
and the correct prediction of the Casimir force in a state of thermal
equilibrium.
