Quantum States: Are they the real thing?

What is the quantum state? There is no widely agreed answer to this question, despite the ubiquitous and crucial role this mathematical object plays in our lives. Two broad schools of thought can be identified. The "ontic view" is that the quantum state describes (partially or completely) the real physical state of affairs. The "epistemic view" is that it instead represents some agent's knowledge or information about the physical system in question.