  An alternative to the effective field theory approach to treat ghosts in
higher derivative theories is to attempt to integrate them out via the
Euclidean path integral formalism. It has been suggested that this method could
provide a consistent framework within which we might tolerate the ghost degrees
of freedom that plague, among other theories, the higher derivative gravity
models that have been proposed to explain cosmic acceleration. We consider the
extension of this idea to treating a class of terms with order six derivatives,
and find that for a general term the Euclidean path integral approach works in
the most trivial background, Minkowski. Moreover we see that even in de Sitter
background, despite some difficulties, it is possible to define a probability
distribution for tensorial perturbations of the metric.
