"psi-epistemic" view is that the quantum state does not represent a
state of the world, but a state of knowledge about the world. It is
motivated, in part, by the observation of qualitative similarities between
characteristic properties of non-orthogonal quantum wavefunctions and between
overlapping classical probability distributions. It might be suggested
that this gives a natural explanation for these properties, which seem puzzling
for the alternative "psi-ontic" view. I will examine two such
similarities, quantum state overlap and quantum state discrimination, and ask
how far can we reproduce the quantitative values given by quantum theory.
It will be shown that the psi-epistemic view cannot properly account for
the quantitative values, and so must still rely on the same kind of
explanations as the "psi-ontic" view.