  We elaborate on a proposal made by Greensite and others to solve the problem
of time in quantum gravity. The proposal states that a viable concept of time
and a sensible inner product can be found from the demand for the Ehrenfest
equations to hold in quantum gravity. We derive and discuss in detail exact
consistency conditions from both Ehrenfest equations as well as from the
semiclassical approximation. We also discuss consistency conditions arising
from the full field theory. We find that only a very restricted class of
solutions to the Wheeler-DeWitt equation fulfills all consistency conditions.
We conclude that therefore this proposal must either be abandoned as a means to
solve the problem of time or, alternatively, be used as an additional boundary
condition to select physical solutions from the Wheeler-DeWitt equation.
