  It is argued that the zero point energy in quantum field theory is a
reflection of the particle anti-particle content of the theory. This essential
physical content is somewhat disguised in electromagnetic theory wherein the
photon is its own anti-particle. To illustrate this point, we consider the case
of a charged Boson theory $(\pi^+,\pi^-)$ wherein the particle and
anti-particle can be distinguished by the charge $\pm e$. Starting from the
zero point energy, we derive the Boson pair production rate per unit time per
unit volume from the vacuum in a uniform external electric field. The result is
further generalized for arbitrary spin $s$.
