  Following the argument of Pusey, Barrett and Rudolph (Nature Phys. 8:476,
2012), new interest has been raised on whether one can interpret state-vectors
(pure states) in a statistical way ($\psi$-epistemic theories), or if each of
them corresponds to a different ontological entity. Each interpretation of
quantum theory assumes different ontology and one could ask if the PBR argument
carries over. Here we examine this question for histories formulations in
general with particular attention to the co-event formulation. State-vectors
appear as the initial state that enters into the quantum measure. While the PBR
argument goes through up to a point, the failure to meet some of the
assumptions they made does not allow one to reach their conclusion. However,
the author believes that the "statistical interpretation" is still impossible
for co-events even if this is not proven by the PBR argument.
