  Observer dependence is central to Quantum Mechanics; in particular if we
associate consistent sets with observer worldviews we can think of the
Consistent Histories (CH) interpretation as a formalisation of observer
dependence. However we lack a theory of the observers themselves. In this paper
we begin by building such a theory within General Relativity (GR), and find
that this framework bears close mathematical resemblance to the treatment of
consistent sets in CH. We therefore adapt the CHSH framework to identify the
`gap' between the classical and quantum theories. We find that the CHSH
argument does not hold on a curved background, so that the inequality may be
violated by classical theories.
