Popper wrote extensively on the quantum theory. In Logic der Forschung (LSD) 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 ( QTSP ) incorporated a famous earlier essay, ‘Quantum Mechanics without “the Observer”’ (QM). In addition Popper's development of the propensity interpretation of probability was much influenced by his views on the rôle 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 (BNIQM). In this paper I will look at some of Popper's arguments in a suitably critical spirit. But he would have applauded this. My great regret is that he cannot respond to this paper with criticisms of my arguments! Thought Experiments In 1934 Popper published a short note in Die Naturwissenschaften entitled ‘Zur Kritik der Ungenauigkeitsrelationen’ (KU). This was actually Popper's scientific debut. It contained what Popper later described as ‘a gross mistake for which I have been deeply sorry and ashamed ever since’ ( QTSP , p. 15). Appendix *XII to the 1959 translation of LSD reproduces a letter from Einstein written in 1935 criticising Popper's proposed thought experiment. Although he tells us in his autobiography ( UQ , p. 92) that he defended his experiment against von Weiszäcker and Heisenberg, he immediately concurred with Einstein's criticism.
Popper wrote extensively on the quantum theory. In Logic der Forschung (LSD) 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 ( QTSP ) incorporated a famous earlier essay, ‘Quantum Mechanics without “the Observer”’ (QM). In addition Popper's development of the propensity interpretation of probability was much influenced by his views on the rôle 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 (BNIQM). In this paper I will look at some of Popper's arguments in a suitably critical spirit. But he would have applauded this. My great regret is that he cannot respond to this paper with criticisms of my arguments! Thought Experiments In 1934 Popper published a short note in Die Naturwissenschaften entitled ‘Zur Kritik der Ungenauigkeitsrelationen’ (KU). This was actually Popper's scientific debut. It contained what Popper later described as ‘a gross mistake for which I have been deeply sorry and ashamed ever since’ ( QTSP , p. 15). Appendix *XII to the 1959 translation of LSD reproduces a letter from Einstein written in 1935 criticising Popper's proposed thought experiment. Although he tells us in his autobiography ( UQ , p. 92) that he defended his experiment against von Weiszäcker and Heisenberg, he immediately concurred with Einstein's criticism.
Popper wrote extensively on the quantum theory. In Logic der Forschung (LSD) 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 (QTSP) incorporated a famous earlier essay, ‘Quantum Mechanics without “the Observer”’ (QM). 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 (BNIQM).
Popper wrote extensively on the quantum theory. In Logic der Forschung (LSD) 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 ( QTSP ) incorporated a famous earlier essay, ‘Quantum Mechanics without “the Observer”’ (QM). 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 1 (BNIQM).
Quantum Theory and the Schism in Physics is one of the three volumes of Karl Popper’s Postscript to the Logic of scientific Discovery. The Postscript is the culmination of Popper’s work in the philosophy of physics and a new famous attack on subjectivist approaches to philosophy of science. Quantum Theory and the Schism in Physics is the third volume of the Postscript. It may be read independently, but it also forms part of Popper’s interconnected argument in the Postscript. It presents Popper’s classic statement on quantum physics and offers important insights into his thinking on problems of method within science and physics as a whole.
INTRODUCTION In his essay ‘Quantum Mechanics Without “the Observer”’ (in [20], 7–44), Popper criticizes the Copenhagen Interpretation and suggests construing the quantum theory as a ‘generalization of classical statistical mechanics’ ([20], 16). The uncertainty relations, he says, set ‘limits to the statistical dispersion … of the results of sequences of experiments’ ([20], 20) and not to what can be said about individual systems. Some strange features of orthodox microphysics are due either to a misinterpretation of probability, involving some ‘very simple mistakes’ ([20], 42); or else they are a straightforward consequence of the fact that the quantum theory is a statistical theory. For example, ‘the reduction of the wave packet … has nothing to do with quantum theory: it is a trivial feature of probability theory’ ([20], 37). The idea of probability that is presupposed in all these arguments, however, is Popper's propensity interpretation. Adopting this interpretation suffices for making clear what the quantum theory really is: a ‘generalization of classical statistical mechanics’ ([20], 16). This is Popper's position as I understand it. This position, it seems to me, is attractive enough as long as one does not carry the analysis too far. But it breaks down when confronted with all the facts which Bohr wanted to take into account. Altogether Popper's criticism and his alternative proposals once more reveal the strong points of the Copenhagen philosophy, and especially of the ideas of Niels Bohr. Today it is very difficult to find a satisfactory account of these ideas.
. We put forward a new take on the logic of quantum mechanics, following Schrödinger's point of view that it is composition which makes quantum theory what it is, rather than its particular propositional structure due to the existence of superpositions, as proposed by Birkhoff and von Neumann. This gives rise to an intrinsically quantitative kind of logic, which truly deserves the name ‘logic’ in that it also models meaning in natural language, the latter being the origin of logic, that it supports automation, the most prominent practical use of logic, and that it supports probabilistic inference. The physics and the logic of quantum-ish logic. In 1932 John von Neumann formalized Quantum Mechanics in his book “Mathematische Grundlagen der Quantenmechanik”. This was effectively the official birth of the quantum mechanical formalism which until now, some 75 years later, has remained the same. Quantum theory underpins so many things in our daily lives including chemical industry, energy production and information technology, which arguably makes it the most technologically successful theory of physics ever. However, in 1935, merely three years after the birth of his brainchild, von Neumann wrote in a letter to American mathematician Garrett Birkhoff: “I would like to make a confession which may seem immoral: I do not believe absolutely in Hilbert space no more.” (sic)—for more details see [73]. Soon thereafter they published a paper entitled “The Logic of Quantum Mechanics” [13]. Their ‘quantum logic’ was cast in order-theoretic terms, very much in the spirit of the then reigning algebraic view of logic, with the distributive law being replaced with a weaker (ortho)modular law. This resulted in a research community of quantum logicians [68, 71, 47, 30]. However, despite von Neumann's reputation, and the large body of research that has been produced in the area, one does not find a trace of this activity neither in the mainstream physics, mathematics, nor logic literature. Hence, 75 years later one may want to conclude that this activity was a failure. What went wrong? The mathematics of it. Let us consider the raison d'être for the Hilbert space formalism.
Karl R Popper 1982 London: Hutchinson xviii + 228 pp price £15 This final volume of Sir Karl Popper's long-awaited Postscript to The Logic of Scientific Discovery appears through the editorial efforts of W W Bartley III, and constitutes a major addition to Popper's published corpus, of particular interest to theoretical physicists, historians of the quantum revolution, and philosophers of science. In it, a basic theme of Popper's philosophy, that something can come from nothing, is related to the present situation in physical theory.