Abstract
Since its early formulation, non-relativistic quantum mechanics (QM) has been the source of sustained controversy about its foundation. Despite its impressive empirical success, several foundational issues have not been settled by the theory: What exactly happens with the observables when a quantum system is not being measured? And what exactly happens during measurement? What is the nature of quantum particles? In particular, are they individuals or not? And can identity be applied to these particles? Not surprisingly, a variety of interpretations of QM have been developed in the attempt to address these and other foundational questions. Perhaps also not surprisingly, so far there has been no agreement as to which of these interpretations (if any) should be preferred.
