  We address the issue of recovering the time-dependent Schr\"{o}dinger
equation from quantum gravity in a natural way. To reach this aim it is
necessary to understand the nonoccurrence of certain superpositions in quantum
gravity.
  We explore various possible explanations and their relation. These are the
delocalisation of interference terms through interaction with irrelevant
degrees of freedom (decoherence), gravitational anomalies, and the possibility
of $\theta$ states. The discussion is carried out in both the geometrodynamical
and connection representation of canonical quantum gravity.
