Now that Bohr's philosophy of quantum physics has been surveyed in detail, it is time to provide a general description of his philosophy that illuminates the details. The question which I wish to address, then is: what is the general philosophy, or philosophical point of view, that underlies Bohr's philosophy of physics? Can his philosophy be neatly categorised in terms of any well known philosophical position? Apropos his philosophy of physics in particular, the question of primary interest is: to what extent, if any, is Bohr's philosophy of physics realist? No simple answer to this question can be given: indeed, certain realist and non-realist components are subtly interwoven in his philosophy, and to unravel them we shall need a fairly refined conception of what constitutes a realist interpretation of physics. Realism in the interpretation of physics The basis of realism is the view that statements of a certain class predicate properties of real objects, the truth-values of these statements being determined by reality as it is independently of how it appears to us to be. This notion is captured in the following characterisation of what constitutes the adoption of a realist interpretation of a physical theory.
Now that Bohr's philosophy of quantum physics has been surveyed in detail, it is time to provide a general description of his philosophy that illuminates the details. The question which I wish to address, then is: what is the general philosophy, or philosophical point of view, that underlies Bohr's philosophy of physics? Can his philosophy be neatly categorised in terms of any well known philosophical position? Apropos his philosophy of physics in particular, the question of primary interest is: to what extent, if any, is Bohr's philosophy of physics realist? No simple answer to this question can be given: indeed, certain realist and non-realist components are subtly interwoven in his philosophy, and to unravel them we shall need a fairly refined conception of what constitutes a realist interpretation of physics. Realism in the interpretation of physics The basis of realism is the view that statements of a certain class predicate properties of real objects, the truth-values of these statements being determined by reality as it is independently of how it appears to us to be. This notion is captured in the following characterisation of what constitutes the adoption of a realist interpretation of a physical theory.
Now that my account of Bohr's philosophy of physics has been completed, it remains for me to give a general assessment of it. What value should we assign to Bohr's main ideas – the notions of correspondence and complementarity? How does his interpretation of quantum physics fare in comparison with some of its rivals? What should our assessment of the Bohr–Einstein debate be? I shall take up these questions in the reverse order. Einstein or Bohr? The final verdict The Bohr–Einstein debate is primarily a dispute about the philosophical foundations in terms of which the interpretation of quantum mechanics should be based: specifically it is a dispute about the intrinsic-properties theory, i.e. about the scope of a realist interpretation of quantum mechanics. Einstein wished to maintain the two realist theses, the intrinsic-properties theory and the objective-values theory, whereas Bohr wished to hold only the latter. My own philosophical leanings are in the direction of realism. To my mind the notion of a physical reality the existence and constitution of which are independent of human thought and perception is coherent and plausible: what physical objects there are, and what properties they have, is not determined by human thought or perception, or by human practical interests. I have sympathy, therefore, with Einstein's position concerning the indefinability thesis and the question of the completeness of quantum mechanics.
This book gives a clear and comprehensive exposition of Niels Bohr's philosophy of physics. Bohr's ideas are of major importance, for they are the source of the Copenhagen interpretation of quantum physics; yet they are obscure, and call for the sort of close analysis that this book provides. The book describes the historical background of the physics from which Bohr's ideas grew. The core of the book is a detailed analysis of Bohr's arguments for complementarity and of the interpretation which he put upon it. Special emphasis is placed throughout on the contrasting views of Einstein, and the great debate between Bohr and Einstein is thoroughly examined. The book traces the philosophical influences on Bohr, and unravels the realist and anti-realist strands in his thinking. Bohr's philosophy is critically assessed in the light of recent developments in the foundations of quantum physics (the work of Bell and others) and in philosophy (the realism-anti-realism debate) and it is revealed as being much more subtle and sophisticated than it is generally taken to be. While the book will be of interest to specialists, it is written in a style that will make it accessible to those who have no specialist knowledge of the relevant physics and philosophy.
The surprising thing is that the most successful scientific field of the century is quantum physics, and quantum physics in its most orthodox interpretation is decidedly anti-realist. At least that is what Niels Bohr, the foremost thinker in the field, said explicitly: "an independent reality in the ordinary physical sense can neither be ascribed to the phenomena nor to the agencies of observation." Many philosophers, however, would cringe at the thought that any form of relativism may be considered sensible. Their support for realism stems in part from the belief that the alternative to realism is relativism and that relativism is incoherent. Likewise at the level of science, a view may allow the bat such striking success in dealing with certain difficult questions that the bat adopts it as his means of viewing that entire area of experience.
Niels Bohr thought that what quantum mechanics has taught us is not only to understand something new, but also a new meaning of the term “to understand”. Bohr wanted to free himself from ontology by putting emphasis on epistemology; i.e. on certain conditions for observation and description. He believed that the epistemological lesson of quantum mechanics was a crucial one. Basically it has two important aspects. 1. Bohr's philosophy leads to a break with the so-called correspondence theory for truth and meaning. It states that true propositions are descriptions of a world that is independent of our observations; i.e. that on a regular basis one can compare with reality, that is, in compare the two areas against each other. Bohr believed that this did not make sense, since in many situations cannot add meaning to a world that has a sich structure (the thing-in-itself), which in turn can be depicted when observed. 2. All knowledge is attained under certain conditions for description. Bohr thought that the long-lasting criterion for valid knowledge is that can communicate it unambiguously to each other. When Bohr emphasised that we are suspended in language in the sense that all knowledge determines what can say about the world in an understandable way, and not what the world actually is, this must be understood in the sense that only know the world as recognised; i.e., structured on the basis of the conditions for description, to which are, as part of the world, necessarily are subjected to. Bohr's emphasis on conditions for descriptions invalidates the well-known distinction between analytic and synthetic propositions. An important feature of the descriptive use of ordinary language, as well as in classical physics, is that description is based on a dividing line between subject and object. This results in idealism and materialism not being tenable positions. Furthermore, it is such that cannot use the designation of things independently of the designation of time and space. Logical principles are only meaningfully applied in situations relating to our conditions for observation. So based on inspiration from Bohr, Favrholdt developed a more adequate and comprehensive philosophy, where he, among other things, states that all humans possess a fundamental language, underlying all languages. This constitutes a number of concepts – the core – where the correct use is dictated by the structure of the world, which humans learn through sensory perception and action.
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.
The Bohr-Einstein debate on the interpretation of quantum mechanics may be viewed as a discussion on the epistemological status of knowledge gained by physics. It is shown that in fact the advent of quantum theory has led, in a new context, to an old philosophical controversy between epistemological realism (held by Einstein) and phenomenalism (held by Bohr). An inquiry into this controversy, taking into account the contemporary understanding of quantum mechanics based on the axiomatic study of its foundations, leads to the conclusion that contrary to widespread opinion, it is perfectly possible to formulate quantum mechanics in an entirely realistic manner according to the postulate of Einstein. We demonstrate that Bohr's episteme-logy, in which the role of experimental arrangements in the physical description is taken as a starting point, does not necessarily imply phenomenlism, but may be justifiably considered as a complementary standpoint to the realistic epistemology of Einstein, which is based on the notion of a mental construction which pictures reality.