Measurement
If a quantum state completely specified the properties of a system to which it was assigned then application of quantum theory to an interaction intended to correlate properties of a measured system to those of a measuring device would leave that device recording no determinate outcome, contrary to what we observe. This is the quantum measurement problem. But the problem does not arise if the function of a quantum state assignment is not descriptive but prescriptive, so that all quantum state assignments are relational. Models of decoherence can certify the empirical significance of rival claims about which measurement outcome a device records, but their application does not explain but presupposes that exactly one such claim is true. The reality criterion which Einstein and colleagues applied to show the incompleteness of quantum description of reality is inapplicable to their chosen system while a slightly modified criterion is false.