The quantum theory of a spatially flat Friedmann-Robertson-Walker univ
erse with a massless scalar field as the source is further investigate
d. The classical model is singular and in the framework of a genuine c
anonical quantization (Arnowitt-Deser-Misner formalism) a discussion i
s made of the cosmic evolution, particularly of the quantum gravitatio
nal collapse problem. It is shown that in a matter-time gauge such tha
t time is identified with the scalar field the classical model is sing
ular either at t = -infinity or at t = +infinity, but the quantum mode
l is nonsingular. The latter behavior disproves a conjecture according
to which quantum cosmological singularities are predetermined on the
classical level by the choice of time.