Ontological Models in Quantum Mechanics: What do they tell us?

Abstract

The consequences of the theorems about ontological models are studied. "Maximally $\psi$-epistemic" is shown to be equivalent to the conjunction of two other conditions, each of which can be realized in Hilbert spaces of arbitrary dimension, but which cannot occur together for d>2. I argue that current theorems do not invalidate an epistemic interpretation of quantum states. A new condition, called "functionally $\psi$-epistemic", is introduced, which, were it to be excluded, would signal the exclusion of epistemic interpretations.