Popper wrote extensively on the quantum theory. In Logic der Forschung he devoted a whole chapter to the topic, while the whole of Volume 3 of the Postscript to the Logic of Scientific Discovery is devoted to the quantum theory. This volume entitled Quantum Theory and the Schism in Physics incorporated a famous earlier essay, ‘Quantum Mechanics without “the Observer”’ . In addition Popper's development of the propensity interpretation of probability was much influenced by his views on the role of (...) probability in quantum theory, and he also wrote an insightful critique of the 1936 paper of Birkhoff and von Neumann on nondistributive quantum logic. (shrink)

Popper conceived an experiment whose analysis led to a result that he deemed absurd. Popper wrote that his reasoning was based on the Copenhagen interpretation and therefore invalidated it. Many authors who have examined Popper's analysis have found in it various technical flaws which are briefly summarized here. However, the aim of the present article is not technical. My concern is to redress logical flaws in Popper's argument: the terminology he uses is ambiguous, his analysis involves counterfactual hypotheses, and it (...) violates Bohr's complementarity principle. Therefore, the absurdity of Popper's result only confirms Bohr's approach. (shrink)