A simple and natural introduction to the concept and formalism of spontaneous
wave function collapse can and should be based on textbook knowledge of
standard quantum state collapse and monitoring. This approach explains the
origin of noise driving the paradigmatic stochastic Schr\"odinger equations of
spontaneous localization of the wave function Ψ. It reveals, on the other
hand, that these equations are empirically redundant and the master equations
of the noise-averaged state ρ^ are the only empirically testable
dynamics in current spontaneous collapse theories.Comment: Almost the published version p3-11 in "Collapse of the Wave
Function", ed.: S Gao, Cambridge University Press, 201