  The different roles and natures of spacetime appearing in a quantum field
theory and in classical physics are analyzed implying that a quantum theory of
gravitation is not necessarily a quantum theory of curved spacetime. Developing
an alternative approach to quantum gravity starts with the postulate that
inertial and gravitational energy-momentum need not be the same for virtual
quantum states. Separating their roles naturally leads to the quantum gauge
field theory of volume-preserving diffeomorphisms of an inner four-dimensional
space. The classical limit of this theory coupled to a quantized scalar field
is derived for an on-shell particle where inertial and gravitational
energy-momentum coincide. In that process the symmetry under volume-preserving
diffeomorphisms disappears and a new symmetry group emerges: the group of
coordinate transformations of four-dimensional spacetime and with it General
Relativity coupled to a classical relativistic point particle.
