  We show that the luminosity of a star forming galaxy is capped by the
production and subsequent expulsion of cosmic rays from its interstellar
medium. By defining an Eddington luminosity in cosmic rays, we show that the
star formation rate of a given galaxy is limited by its mass content and the
cosmic ray mean free path. When the cosmic ray luminosity and pressure reaches
a critical value as a result of vigorous star formation, hydrostatic balance is
lost, a cosmic ray-driven wind develops, and star formation is choked off.
Cosmic ray pressure-driven winds are likely to produce wind velocities
significantly in excess of the galactic escape velocity.
  It is possible that cosmic ray feedback results in the Faber-Jackson relation
for a plausible set of input parameters that describe cosmic ray production and
transport, which are calibrated by observations of the Milky Way's interstellar
cosmic rays as well as other galaxies.
