  The assumption that an ensemble of classical particles is subject to
nonclassical momentum fluctuations, with the fluctuation uncertainty fully
determined by the position uncertainty, has been shown to lead from the
classical equations of motion to the Schroedinger equation. This 'exact
uncertainty' approach may be generalised to ensembles of gravitational fields,
where nonclassical fluctuations are added to the field momentum densities, of a
magnitude determined by the uncertainty in the metric tensor components. In
this way one obtains the Wheeler-DeWitt equation of quantum gravity, with the
added bonus of a uniquely specified operator ordering. No a priori assumptions
are required concerning the existence of wavefunctions, Hilbert spaces,
Planck's constant, linear operators, etc. Thus this approach has greater
transparency than the usual canonical approach, particularly in regard to the
connections between quantum and classical ensembles. Conceptual foundations and
advantages are emphasised.
