  We consider the most general dilaton gravity theory in 1+1 dimensions. By
suitably parametrizing the metric and scalar field we find a simple expression
that relates the energy of a generic solution to the magnitude of the
corresponding Killing vector. In theories that admit black hole solutions, this
relationship leads directly to an expression for the entropy $S=2\pi \tau_0/G$,
where $\tau_0$ is the value of the scalar field (in this parametrization) at
the event horizon. This result agrees with the one obtained using the more
general method of Wald. Finally, we point out an intriguing connection between
the black hole entropy and the imaginary part of the ``phase" of the exact
Dirac quantum wave functionals for the theory.
