  Ghosts have been a stumbling block in the development of a UV complete
quantum field theory for gravity. We discuss how difficulties associated with
ghosts are overcome in the context of 0+1d QFT. Obtaining a probability
interpretation is the key issue, and for this we discuss how an appropriate
inner product can be constructed to define a sensible Born rule. Ghost theories
are intrinsically unitary and perturbatively stable. They can also display
nonperburbative stability even when the corresponding normal theory does not.
The spectra and propagators are numerically obtained at both weak and strong
coupling. Normalizable wave functions are obtained for the energy eigenstates
and they show a violation of normal parity. We discuss connections to
PT-symmetric quantum mechanics.
