  J. v. Neumann justified the collapse postulate by the empirical fact of the
repeatability of a measurement at a single quantum system. However, in his
quantum mechanical treatment of the measurement process repeatability emerges
without collapse. The entangled state of the measurement device and the
measured system after their interaction ensures it already. Furthermore, this
state gives the same predictions for the measured system alone as the
description demanded by the collapse postulate.
