“All clocks are clouds”

In other words, I am an indeterminist—like Peirce, Compton, and most other contemporary physicists; and I believe, with most of them, that Einstein was mistaken in trying to hold fast to determinism. (l may perhaps say that I discussed this matter with him, and that I did not find him adamant.) But I also believe that those modern physicists were badly mistaken who pooh-poohed as antediluvian Einstein’s criticism of the quantum theory. Nobody can fail to admire the quantum theory, and Einstein did so wholeheartedly; but his criticism of the fashionable interpretation of the theory—the Copenhagen interpretation—like the criticisms offered by de Broglie, Schrodinger, Bohm, Vigier, and more recently by Landé, have been too lightly brushed aside by most physicists.¹⁷ There are fashions in science, and some scientists climb on the band wagon almost as readily as do some painters and musicians. But although fashions and bandwagons may attract the weak, they should be resisted rather than encouraged;¹⁸ and criticism like Einstein’s is always valuable: one can always learn something from it.

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¹⁷ See also [Popper's] book The Logic of Scientific Discovery, especially the new Appendix *xi; also chapter ix of this book which contains criticism that is valid in the main, though, in view of Einstein’s criticism in Appendix *xii, I had to withdraw the thought experiment (of 1934) described in section 77. This experiment can be replaced, however, by the famous thought experiment of Einstein, Podolsky, and Rosen, discussed there in Appendix *xi and *xii. See also my paper ‘The Propensity Interpretation of the Calculus of Probability, and the Quantum Theory’, in Observation and Interpretation, ed. by S. Korner, 1957, pp. 65-70, and 83-9.

¹⁸ The last sentence is meant as a criticism of some of the views contained in Thomas S. Kuhn’s interesting and stimulating book The Structure of Scientific Revolutions, 1963.

pp. 216-217

Karl Popper, “Of Clouds and Clocks”
Arthur Compton Memorial Lecture, Washington University, 1965