An unpublished debate brought to light: Karl Popper's enterprise against the logic of quantum mechanics

• Published in: Studies in History and Philosophy of Modern Physics 2020-05, Vol.70, p.65-78
• Main Author: Del Santo, Flavio
• Format: Article
• Language: English
• ISSN: 1355-2198; 1879-2502
• DOI: 10.1016/j.shpsb.2020.03.001

Karl Popper published, in 1968, a paper that allegedly found a flaw in a very influential article of Birkhoff and von Neumann, which pioneered the field of “quantum logic”. Nevertheless, nobody rebutted Popper's criticism in print for several years. This has been called in the historiographical literature an “unsolved historical issue”. Although Popper's proposal turned out to be merely based on misinterpretations and was eventually abandoned by the author himself, this paper aims at providing a resolution to such historical open issues. I show that (i) Popper's paper was just the tip of an iceberg of a much vaster campaign conducted by Popper against quantum logic (which encompassed several more unpublished papers that I retrieved); and (ii) that Popper's paper stimulated a heated debate that remained however confined within private correspondence. •Karl Popper allegedly found a mathematical mistake in a pivotal paper by Birkhoff and von Neumann.•Popper critique to the logic of quantum mechanics was much broader than believed.•Physicists criticized Popper but the debate remained confined to private correspondence.•Unpublished papers by Popper and his critique.