  This is a non-technical presentation (in historical context) of the quantum
theory that is strictly based on global unitarity. While the first part was
written for a general readership, Sect. 5 may appear a bit provocative. I argue
that the single-particle wave functions of quantum mechanics have to be
correctly interpreted as field modes that are "occupied once" (that is, first
excited states of the corresponding quantum oscillators in the case of a boson
field). Multiple excitations lead non-relativistically to apparent
many-particle wave functions, while the quantum states proper are defined by
wave function(al)s on the configuration space of fundamental fields, or on
another, as yet elusive, fundamental basis.
