When I was staying at Yukawa's Institute in Kyoto two years ago, I had occasion to discuss Bohr's ideas with the great Japanese physicist, whose conception of the meson with its complementary aspects of elementary particle and field of nuclear force is one of the most striking illustrations of the fruitfulness of the new way of looking at things that we owe to Niels Bohr. I asked Yukawa whether the Japanese physicists had experienced the same difficulty as their Western colleagues in assimilating the idea of complementarity and in adapting themselves to it. He answered, “No, Bohr's argumentation has always appeared quite evident to us;” and, as I expressed surprise, he added, with his aristocratic smile, “You see, we in Japan have not been corrupted by Aristotle.”
When I was staying at Yukawa's Institute in Kyoto two years ago, I had occasion to discuss Bohr's ideas with the great Japanese physicist, whose conception of the meson with its complementary aspects of elementary particle and field of nuclear force is one of the most striking illustrations of the fruitfulness of the new way of looking at things that we owe to Niels Bohr. I asked Yukawa whether the Japanese physicists had experienced the same difficulty as their Western colleagues in assimilating the idea of complementarity and in adapting themselves to it. He answered, “No, Bohr's argumentation has always appeared quite evident to us;” and, as I expressed surprise, he added, with his aristocratic smile, “You see, we in Japan have not been corrupted by Aristotle.”
Complementarity and Deconstruction: Plotnitsky's Analysis and Beyond Makoto Katsumori Akita University The philosophical thought of the modern physicist Niels Bohr (1885–1962), which revolves around the concept of complementarity, has long been a major subject of historical and philosophical inquiry. Many prior studies of Bohr's complementarity, however, seem to be limited by the fact that they largely proceed within the conceptual frames of the "mainstream" philosophy of science. This being the case, his radical questioning of traditional scientific and philosophical notions—such as the unambiguity of concepts and words—has not been adequately addressed, insofar as these notions are uncritically presupposed by the commentators themselves. In other words, Bohr's thought has often been interpreted under certain tacit premises of scientific rationality that are precisely of the kind targeted by his epistemological critique. In recent years, however, there have emerged new approaches to Bohr's idea of complementarity that place it in different, less conventional, philosophical contexts. Among the most notable of these is Arkady Plotnitsky's endeavor to connect Bohr's complementarity with Jacques Derrida's project of deconstruction. In the present article, based on my recent doctoral dissertation,1 I take up this contribution by Plotnitsky as a suitable point of reference from which to [End Page 435] explore anew Bohr's thought with its radical philosophical implications. After outlining Bohr's complementarity argument and Plotnitsky's reading thereof (in the first and second sections, respectively), I will examine a series of problems that seem to face, or to be left unsolved by, Plotnitsky's account (in the third section). This critical appraisal will finally lead me to sketch a new interpretive approach of my own (in the fourth section), which both extends and delimits the intersections between complementarity and deconstruction. As regards the historical development of Bohr's complementarity, I will largely restrict myself to the period between 1927 and 1950, in which the most crucial of his innovative ideas seem to have been presented. I. Bohr's Idea of Complementarity In his 1927 lecture delivered in Como, Italy, entitled "The Quantum Postulate and the Recent Development of Atomic Theory," Niels Bohr introduced the concept and framework of complementarity as a pivotal idea in his interpretation of quantum theory. From then on, he continually developed the idea of complementarity with regard not only to quantum theory but to other fields of knowledge as well. In what follows, I will first outline his complementarity argument in its "early" period, stretching from 1927 to the mid-thirties,—or, more precisely, until just before his 1935 debate with EPR.2 Bohr starts by noting that "our usual description of physical phenomena is based entirely on the idea that the phenomena concerned may be observed without disturbing them appreciably."3 This notion of physical phenomena as undisturbed by observation underlies all of classical physics and is still maintained in the theory of relativity. However, Bohr continues, a new situation has arisen with the development of quantum theory, specifically with "the so-called quantum postulate, which attributes to any atomic process an essential discontinuity, or rather individuality, completely foreign to the classical theories"; this "individuality" implies that "any observation of atomic phenomena will involve an interaction with the [End Page 436] agency of observation not to be neglected" (PWNB, 1: 53–54.). In more specific terms, any observation aimed at space-time coordination brings about an exchange of momentum and energy with the measuring rods and clocks. It is crucial here that this interaction between the object and the instrument of observation is not simply unavoidable, but "uncontrollable," which represents a "feature of irrationality" brought into the description of nature (PWNB, 1: 68, 91). For insofar as the measuring instruments are to fulfill their purpose, the interaction itself cannot be taken into account, and thus the magnitude of the disturbance always remains unknown. It follows, in Bohr's view, that "an independent reality in the ordinary physical sense can neither be ascribed to the phenomena nor to the agencies of observation...
Once I tried to teach some quantum mechanics to a class of law students, philosophers, and art historians. As an advertisement for the course I put together the most sensational quotations I could collect from the most authoritative practitioners of the subject. Heisenberg was a goldmine: “The concept of the objective reality of the elementary particles has thus evaporated…”; “the idea of an objective real world whose smallest parts exist objectively in the same sense as stones or trees exist, independently of whether or not we observe them … is impossible …” Feynman did his part too: “I think I can safely say that nobody understands quantum mechanics.” But I failed to turn up anything comparable in the writings of Bohr. Others attributed spectacular remarks to him, but he seemed to take pains to avoid any hint of the dramatic in his own writings. You don't pack them into your classroom with “The indivisibility of quantum phenomena finds its consequent expression in the circumstance that every definable subdivision would require a change of the experimental arrangement with the appearance of new individual phenomena,” or “the wider frame of complementarity directly expresses our position as regards the account of fundamental properties of matter presupposed in classical physical description but outside its scope.” I was therefore on the lookout for nuggets when I sat down to review these three volumes – a reissue of Bohr's collected essays on the revolutionary epistemological character of the quantum theory and on the implications of that revolution for other scientific and non-scientific areas of endeavor (the originals first appeared in 1934, 1958, and 1963.)
Recently it has been discovered that Niels Bohr, the father of quantum physics, was acquainted, at a young age, with the ancient Chinese philosophy of Lao-Tzu.New evidence has come to light from a letter written by Bohr himself, discovered in 1998, which is a reply to a letter of inquiry from a Svend Hugo Jiirgensen, a teacher from the Danish town of Aalborg.The teacher had sent Bohr a manuscript entitled 'Tuo Te Ching and the Idea of Complementarity'.Bohr's reply, dated 26 March 1958 begins, "I thank you for your letter and the enclosed little note about Tuo Te Ching, which I have read with great interest.I believe what you say about the old Chinese philosophy is in many ways quite to the point.In my youth I received a beautiful impression of it through Ernst Merller's book 'Oldmester', and at a visit to China twenty years ago I learned how highly the memory of Lao-Tzu is still valued."Since Merller's book was first published in 1909 (the year Bohr turned 24) and Bohr by his own account was in his youth, it is clear that his knowledge of Chinese philosophy preceded his discovery of the complementarity principle in physics ( 1927).While this does not conclusively prove that he learned his idea of complementarity from Chinese philosophy, it is nonetheless a document of great interest.In any event, it is clear that Bohr valued highly ancient Chinese philosophy.It was either instrumental or decisive for his complementarity principle in physics, which has proved invaluable as an explanatory principle for Western physics.What better proof is needed to illustrate that the "Chinese mind" is not "of a different order of humanity" than its accessibility through the medium of Danish language to a Western physicist?That the same Western physicist could then apply the idea of complementarity to understand the workings of the universe common to both Western and Chinese minds is a further demonstration that the Chinese mind is as universal in its application to reality as its Western counterpart.And what better evidence can be cited to show that the
Niels Bohr and the Philosophy of Physics: Twenty-First-Century Perspectives examines the philosophical views, influences and legacy of the Nobel Prize physicist and philosophical spokesman of the quantum revolution, Niels Bohr. The sixteen contributions in this collection by some of the best contemporary philosophers and physicists writing on Bohr’s philosophy today all carefully distinguish his subtle and unique interpretation of quantum mechanics from views often imputed to him under the banner of the “Copenhagen Interpretation.” With respect to philosophical influences on Bohr’s outlook, the contributors analyse prominent similarities between his viewpoint and Kantian ways of thinking, the views of the Danish philosopher Harald Høffding, and themes characteristic of American pragmatism. In recognizing the importance of Bohr’s epistemological naturalism they examine his defence of the indispensability of classical concepts from a variety of different perspectives. This collection shows us that Bohr’s interpretation of quantum mechanics, now nearly a century old, still has
Niels Bohr and Philosophy of Physics: Twenty-First Century Perspectives examines the philosophical views, influences and legacy of the Nobel Prize physicist and philosophical spokesman of the quantum revolution, Niels Bohr. The sixteen contributions in this collection by some of the best contemporary philosophers and physicists writing on Bohr's philosophy today all carefully distinguish his subtle and unique interpretation of quantum mechanics from views often imputed to him under the banner of the “Copenhagen Interpretation.” With respect to philosophical influences on Bohr's outlook, the contributors analyse prominent similarities between his viewpoint and Kantian ways of thinking, the views of the Danish philosopher Harald Høffding, and themes characteristic of American pragmatism. In recognizing the importance of Bohr's epistemological naturalism they examine his defence of the indispensability of classical concepts from a variety of different perspectives. This collection shows us that Bohr's interpretation of quantum mechanics, now nearly a century old, still has the power to shed light on a variety of issues that have arisen only since his lifetime, as well as decoherence theory and other non-collapse interpretations. Balancing historical themes with contemporary discussions, Niels Bohr and the Philosophy of Physics establishes Bohr's on-going contribution to the philosophy of physics and examines his place in the history of philosophy.
Part I. Niels Bohr. Communications delivered to the Royal Danish Academy of sciences and letters, October 3, 1985 (edited by E. Dal). Niels Bohr and The Royal Danish Academy of Sciences and Letters (B. Strmgren). Epistemological considerations (H.B.G. Casimir). Part II. The Lesson of Quantum Theory. Proceedings of the Niels Bohr centenary symposium, October 4-7, 1985 (edited by J. de Boer and O. Ulfbeck). The Lesson of Quantum Theory. Measurement in quantum theory and the problem of complex systems (P.W. Anderson). Quantum mechanics at the macroscopic level (A.J. Leggett). Strange quantum numbers in condensed matter and field theory (J.R. Schrieffer). The study of the nucleus as a theme in contemporary physics (B.R. Mottelson). ``Complementarity'' between energy and temperature (J. Lindhard). Radiation by uniformly moving sources (V.L. Ginzburg). Does elementary particle physics have a future? (S.L. Glashow). Observability of quarks (J.D. Bojrken). The transformation of elementary particle physics into many-body physics (L. Van Hove). Physics in terms of difference equations (T.D. Lee). Some lessons of renormalization theory (A.S. Wightman). Particles, fields and now strings (S. Weinberg). Collective and planetary motion in atoms (R.S. Berry). Unity of Knowledge. The origin and evolution of large-scale structure in the universe (W.L.W. Sargent). Molecular replication and the origins of life (L.E. Orgel). Physics, biological computation and complementarity (J.J. Hopfield). Complementarity in linguistic observation, description and explanation (W.U. Dressler). Niels Bohr. Great connections come alive: Bohr, Ehrenfest and Einstein (M.J. Klein). Niels Bohr and nuclear weapons (M. Gowing). Niels Bohr: The man and his legacy (J.A. Wheeler). Mellem Spog og Alvor: Personal recollections about Niels Bohr (H.B.G. Casimir). Part III. Jest and Earnest. AAddresses presented at the evening gathering in Ny Carlsberg Glyptoteket, October 7, 1985. (edited by J. de Boer and O. Ulfbeck). Parentesen (A. Aaboe). Truth and clarity (R. Peierls). Niels Bohr, the quantum and the world (V.F. Weisskopf).