  Karl Popper and Paul Feyerabend have been among the most influential
philosophers of science of the twentieth century. Extensive studies have been
dedicated to the development of their controversial relationship, which saw
Feyerabend turning from a student and supporter of Popper to one of his
harshest critics. Yet, it is not as well known that the rift between Popper and
Feyerabend generated mainly in the context of their studies on the foundation
of quantum mechanics, which has been the main subject of their discussions for
about two decades. This paper reconstructs in detail their diatribe over the
foundations of quantum mechanics, emphasizing also the major role that their
personal relationship played in their distancing.
