 This gives a nice way of posing the question of quantum state realism: are there preparations corresponding to distinct pure quantum states that can give rise to the same ontic state, or, conversely, are there ontic states compatible with distinct quantum states? Pusey, Barrett, and Rudolph (2012) showed that, if one adopts a seemingly natural independence assumption about state preparations—namely, the assumption that it is possible to prepare a pair of systems in such a way that the probabilities for ontic states of the two systems are effectively independent—then the answer is negative; any ontological model that reproduces quantum predictions and satisfies this Preparation Independence assumption must be a \(\psi\)-ontic model.