What is commonly known as the Copenhagen interpretation of quantum mechanics, regarded as representing a unitary Copenhagen point of view, differs significantly from Bohr's complementarity interpretation, which does not employ wave packet collapse in its account of measurement and does not accord the subjective observer any privileged role in measurement. It is argued that the Copenhagen interpretation is an invention of the mid‐1950s, for which Heisenberg is chiefly responsible, various other physicists and philosophers, including Bohm, Feyerabend, Hanson, and Popper, having (...) further promoted the invention in the service of their own philosophical agendas. (shrink)

On several occasions I have pointed out that the lesson taught us by recent developments in physics regarding the necessity of a constant extension of the frame of concepts appropriate for the classification of new experiences leads us to a general epistemological attitude which might help us to avoid apparent conceptual difficulties in other fields of science as well. Since, however, the opinion has been expressed from various sides that this attitude would appear to involve a mysticism incompatible with the (...) true spirit of science, I am very glad to use the present opportunity of addressing this assembly of scientists working in quite different fields but united in their striving to find a common ground for our knowledge, to come back to this question, and above all to try to clear up the misunderstandings which have arisen. (shrink)

As the theory of the atom, quantum mechanics is perhaps the most successful theory in the history of science. It enables physicists, chemists, and technicians to calculate and predict the outcome of a vast number of experiments and to create new and advanced technology based on the insight into the behavior of atomic objects. But it is also a theory that challenges our imagination. It seems to violate some fundamental principles of classical physics, principles that eventually have become a part (...) of western common sense since the rise of the modern worldview in the Renaissance. So the aim of any metaphysical interpretation of quantum mechanics is to account for these violations. (shrink)

This ground-breaking book brings together researchers from a wide range of disciplines to discuss the control and coordination of processes involved in perceptually guided actions. The research area of motor control has become an increasingly multidisciplinary undertaking. Understanding the acquisition and performance of voluntary movements in biological and artificial systems requires the integration of knowledge from a variety of disciplines from neurophysiology to biomechanics.

SummaryA short exposition is given of the foundation of the causal description in classical physics and the failure of the principle of causality in coping with atomic phenomena. It is emphasized that the individuality of the quantum processes excludes a separation between a behaviour of the atomic objects and their interaction with the measuring instruments denning the conditions under which the phenomena appear. This circumstance forces us to recognize a novel relationship, conveniently termed complementarity, between empirical evidence obtained under different (...) experimental conditions. An appropriate tool for a complementary mode of description is provided by the quantum‐mechanical formalism which allows us to account for regularities of definite or statistical character beyond the grasp of classical physical explanation. – N. B. (shrink)

An attempt is made to give a coherent account of the logical essence of the Copenhagen interpretation of quantum theory. The central point is that quantum theory is fundamentally pragmatic, but nonetheless complete. The principal difficulty in understanding quantum theory lies in the fact that its completeness is incompatible with external existence of the space—time continuum of classical physics.

According to the standard view, the so-called ‘Copenhagen interpretation’ of quantum mechanics originated in discussions between Bohr and Heisenberg in 1927, and was defended by Bohr in his classic debate with Einstein. Yet recent scholarship has shown Bohr’s views were never widely accepted, let alone properly understood, by his contemporaries, many of whom held divergent views of the ‘Copenhagen orthodoxy’. This paper examines how the ‘myth of the Copenhagen interpretation’ was constructed by situating it in the context of Soviet Marxist (...) critique of quantum mechanics in the 1950s and the response by physicists such as Heisenberg and Rosenfeld. (shrink)

Abstract: This paper assesses the Everettian approach to the measurement problem, especially the version of that approach advocated by Simon Saunders and David Wallace. I emphasise conceptual, indeed metaphysical, aspects rather than technical ones; but I include an introductory exposition of decoherence. In particular, I discuss whether---as these authors maintain---it is acceptable to have no precise definition of 'branch' (in the Everettian kind of sense). (A version of this paper will appear in a CTNS/Vatican Observatory volume on Quantum Theory and (...) Divine Action, ed. Robert Russell et al.). (shrink)

Although there is a complete consensus among working physicists with respect to the practical and operational meanings of quantum states, and also a rather loosely formulated general philosophic view called the Copenhagen interpretation, a great deal of confusion and divergence of opinions exist as to the details of the measurement process and its effects upon quantum states. This paper reviews the current expositions of the measurement problem, limiting itself for lack of space primarily to the writings of physicists; it calls (...) attention to inconsistencies and proposes resolutions. Except for a summary of the properties of statistical matrices which are needed in Part II, the first part is non-mathematical and deals largely with two kinds of probability, reducible and irreducible probabilities, which need to be distinguished for a proper understanding of the measurement act. (shrink)

The trouble with the idea of measurement is its seeming clarity, its obviousness, its implicit claim to finality in any inquisotory discourse. Its status in philosophy of science is taken to be utterly primitive; hence the difficulties it embodies, if any, tend to escape detection and scrutiny. Yet it cannot be primitive in the sense of being exempt from analysis; for if it were every measurement would require to be simply accepted as a protocol of truth, and one should never (...) ask which of two conflicting measurements is correct, or preferable. Such questions are continually being asked, and their propriety in science indicates that even measurement, with its implication of simplicity and adroitness, points beyond itself to other matters of importance on which it relies for validation. (shrink)

The rising interest, in the late 20th century, in the foundations of quantum physics, a subject in which Franco Selleri has excelled, has suggested the fair question: how did it become so? The current answer says that experiments have allowed to bring into the laboratories some previous gedanken experiments, beginning with those about EPR and related to Bell’s inequalities. I want to explore an alternative view, by which there would have been, before Bell’s inequalities experimental tests, a change in the (...) views shared by physicists concerning the intellectual status of that issue. I will take three cases which will serve as the threads of our story: the connections between Bohm’s causal interpretation and Bell’s inequalities; Wigner’s ideas on the measurement problem; and finally Everett’s relative states formulation. In the end, I will discuss how those threads were gathered together by creating foundations of quantum physics as a field of research. (shrink)

It is shown how the development of physics has involved making explicit what were homocentric projections which had heretofore been implicit, indeed inexpressible in theory. This is shown to support a particular notion of the invariant as the real. On this basis the divergence in ideals of physical intelligibility between Bohr and Einstein is set out. This in turn leads to divergent, but explicit, conceptions of objectivity and completeness for physical theory. *I am indebted to Dr. G. McLelland. Professor F. (...) Rohrlich and an anonymous referee of this journal for several improvements in the formulation of the paper. (shrink)

Many works intended to introduce interpretive issues in quantum mechanics present John von Neumann as having a view in which measurement produces a physical collapse in the system being measured. In this paper I argue that such a reading of von Neumann is inconsistent with what von Neumann actually says. I show that much of what he says makes no sense on the physical collapse reading, but falls into place if we assume he does not have such a view. I (...) show that the physical collapse view is based on an understanding of ‘state’ which von Neumann does not share. Introduction The standard reading of von Neumann The standard reading of von Neumann and Chapter VI The Chapter VI argument The Chapter V argument The Chapters III and IV argument Conclusion. (shrink)

In what follows, I examine three main points which may help us to understand the deep nature of Einstein's objections to quantum mechanics. After having played a fundamental pioneer role in the birth of quantum physics, Einstein was, as is well known, far less enthusiastic about its constitution as a quantum mechanics and, since 1927, he constantly argued against the pretention of its founders and proponents to have settled a definitive and complete theory. I emphasize first the importance of the (...) philosophical climate, which was dominated by the Copenhagen orthodoxy and Bohr's idea of complementarity: What Einstein was primarily reluctant to was to accept the fundamental character of quantum mechanics as such, and to modify for it the basic principles of knowledge. I thus stress the main lines of Einstein's own programme in respect to quantum physics, which is to be considered in relation to his other contemporary attempts and achievements. Finally, I show how Einstein's arguments, when dealing with his objections, have been fruitful and some of them still worthy, with regard to recent developments concerning local nonseparability as well as concerning the problems of completeness and accomplishment of quantum theory. (shrink)

This article explains why Bohr does not need to discuss the projection postulate or the "problem of measurement". Beginning with a thumbnail sketch of Bohr 's general views, it is argued that Bohr interprets the state function as giving a statistical summary of experimental outcomes. Against the objection that Bohr was too much a microrealist to endorse such an instrumentalist statistical interpretation it is suggested that he rejected the issue of microrealism as not well formed. It is shown that on (...) his statistical interpretation Bohr does not need the projection postulate or face the usual problem of measurement. (shrink)

This paper analyses the early history of David Bohm’s mechanics from the perspective of Ludwik Fleck’s thought-collectives and shows how the thought-style of the scientific community limits the possible modes of thinking and what new possibilities for the construction of a new theory arise if these limits are removed.

Papers advocating a hidden-variable interpretation of quantum mechanics typically begin by emphasizing that John von Neumann’s no-go theorem does not apply to them. If authors are ontologically minded, their criticism also takes aim at his theory of measurement as expressed in his seminal 1932 book Mathematical Foundations of Quantum Mechanics Additionally, David Bohm and Basil Hiley have recently argued that “in so far as von Neumann effectively gave the quantum state a certain ontological significance, the net result was to produce (...) a confused and unsatisfactory ontology. This ontology is such that the collapse of the wave function must also have an ontological significance.”. (shrink)

How should we read Bohr? The answer to this question is by no means clear, not least because for a long period of time Bohr has not been read but rather mythologized, and his views “almost universally either overlooked or distorted beyond recognition” (Hooker 1972, 132). Even among his readers, though, there is a general feeling of uneasiness with respect to his use of words, and wide disagreement with respect to what he really meant to say. This seems to have (...) always been the case, if we recall what Ehrenfest wrote to Bohr on July 17, 1921: “Now, dear Bohr, every person I know wails only over the fact that you write your things so briefly and compactly that one always has the greatest trouble fetching all of the ideas out of the fruit cake” (Works, 3, 623). Ehrenfest’s remark suggests that our predicament with Bohr’s thought originates in fact in his own style of writing; and accordingly, the many stories told in the doxography about Bohr’s mumbling unintelligible remarks or his endlessly rewriting each of his papers seem to point to some accidental and subjective characteristics of his: he had no deep professional knowledge of the language of philosophy, not enough time, or too much anxiety. But we could also look at Bohr’s struggle with language the other way around, in a very different way. Heisenberg, for instance, noted several times that Bohr was in the process of creating ‘a new language’. (shrink)

My contribution will focus on only one question, which I would like to state in the simplest possible way. This question will be: why do we find Bohr obscure? Or, alternatively, why is there so much — and ever renewed — complaint in the literature over Bohr ‘being unintelligible’?