Quantum Limits of Knowledge 2021 Wednesday 31st March, 2021 I will argue that we have good reason to believe that distinct pure quantum states correspond to distinct physical states. Moreover, contrary to what is suggested by Quantum Bayesians, the arguments for realism about quantum states go through when the probabilities involved are taken to be subjective, if the conclusion is about the agent's beliefs: an agent whose credences conform to quantum probabilities should believe that preparation procedures with which she associates distinct pure quantum states produce distinct states of reality. The conclusion can be avoided only by stipulation of limitations on the agent's theorizing about the world, limitations that are not warranted by the empirical success of quantum mechanics or any other empirical considerations.