  We suggest that the Baldwin Effect is a result of the spectral dependence of
the line-driving ionizing continuum on the black hole mass. We derive a
relationship between the mass of the central black hole and the broad emission
line luminosity in active galactic nuclei (AGN). Assuming the UV spectrum of
AGN is emitted from an optically thick medium we find an expression for the
characteristic energy of the ``UV bump'' in terms of the observable luminosity
and emission-line width. We show empirically and analytically that the bump
energy is anti-correlated with the black-hole mass and with the continuum
luminosity. Our model reproduces the observed inverse correlation between
equivalent width and continuum luminosity, yielding an explanation of the
Baldwin effect from first principles. The model gives a good fit to the Baldwin
Effect of the CIV line for a mean quasar EUV spectrum (Zheng et al. 1997) and
for several model spectra. The model also predicts a correlation between the
strength of the Baldwin Effect (the slope of the equivalent width as a function
of luminosity) and the ionization potential, consistent with recent data.
