As a matter of fact, no serious description of the Einstein-Podolsky-Rosen problem uses the incriminated postulate that the state vector is objective. The most straightforward case is that of realism. Realism, however, is not universally accepted. In Neil Bohr's philosophy, nonseparability is also present, but it has a very different meaning. The nonseparability of the quantum world is thus transferred, in this philosophy, from the system of the microparticles to the systems that each of these micro-objects constitutes with its instrument. In regard to Lorentz invariance, the transition from the pure case to the mixture—the reduction of the wave packet—raises less acute problems in Bohr's philosophy than it does in other approaches. Moreover, Bohr's philosophy obviously implies some restrictions on our freedom to imagine an independent external reality. The reason for this is that this conception endows the instruments with virtues that clearly transcend their status as mere physical systems —indeed, it ultimately defines instruments with reference to the desires.
As a matter of fact, no serious description of the Einstein-Podolsky-Rosen problem uses the incriminated postulate that the state vector is objective. The most straightforward case is that of realism. Realism, however, is not universally accepted. In Neil Bohr's philosophy, nonseparability is also present, but it has a very different meaning. The nonseparability of the quantum world is thus transferred, in this philosophy, from the system of the microparticles to the systems that each of these micro-objects constitutes with its instrument. In regard to Lorentz invariance, the transition from the pure case to the mixture—the reduction of the wave packet—raises less acute problems in Bohr's philosophy than it does in other approaches. Moreover, Bohr's philosophy obviously implies some restrictions on our freedom to imagine an independent external reality. The reason for this is that this conception endows the instruments with virtues that clearly transcend their status as mere physical systems —indeed, it ultimately defines instruments with reference to the desires.
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.
All alternative interpretations have at their roots some form of disgust at the Copenhagen–Gottingen philosophy, and all have a desire to seek an alternative truth for the understanding of quantum mechanics. The alternative view is of an intrinsic reality prior to the measurement, as discussed by A. Einstein, and by most of the founders of the wave theory of quantum mechanics. A key point of Neils Bohr’s arguments with Einstein, particularly with regard to the Einstein–B. Podolsky–N. Rosen type of experiments, was that one could not make multiple measurements on the same particle, or quantum system. In his view, the measurement itself defined the quantum system. With the arrival of the Schrodinger equation, quantum mechanics had a causal, deterministic equation of motion for the wave function. Perturbation theory, based upon the Schrodinger equation, provided transition details that undermined the assertions of quantum jumps.
THE ARGUMENT Opponents of Bohr's interpretation often refer to an argument by Einstein, Podolsky and Rosen, (EPR) according to which, the formalism of wave mechanics is such that it demands the existence of exact simultaneous values of non-commuting variables. Clearly, if this should be the case, then Bohr's interpretation of the uncertainty relations would have to be dropped and it would have to be replaced by the interpretation of Einstein and Popper. At the same time all those difficulties which prompted Bohr to invent the hypothesis of the indefiniteness of state descriptions would reappear. Even worse, it would seem that an inconsistency has been discovered in the very foundations of the quantum theory. For if it should indeed be the case that the only way of combining duality, the quantum postulate and the conservation laws consists in assuming indefiniteness of state descriptions, then the case of Einstein, Podolsky and Rosen would show that wave mechanics is intrinsically unable to allow for a coherent account embracing these three experimental facts. We now turn to a closer analysis of the argument. Assume that a system S (coordinates q, q ′, q ″ …, q n , r, r ′, r n , …, r m ; or ( qr ) for short) which is in the state Φ ( qr ) has been (either mentally, or by physical separation) divided into two subsystems, S ′ ( q ) and S ″ ( r ).
The objective of this article is to demonstrate how the historical debate between materialism and idealism, in the field of Philosophy, extends, in new clothes, to the field of Quantum Physics characterized by realism and anti-realism. For this, we opted for a debate, also historical, between the realism of Albert Einstein, for whom reality exists regardless of the existence of the knowing subject, and Niels Bohr, for whom we do not have access to the ultimate reality of the matter, unless conditioning it to the existence of an observer endowed with rationality, position adopted in the Interpretation of Complementarity (1927) – posture that was expanded in 1935 when Bohr assumed a “relationalist” conception, according to which the quantum state is defined by the relationship between the quantum object and the entire measuring device. This is an extremely important debate, as it further consolidates the results of nascent Quantum Mechanics, guaranteeing Bohr the leadership of the orthodoxy based on the interpretation of complementarity. Here, when dealing with Quantum Theory, we will not make any distinction between the terms Quantum Physics, Quantum Theory or Quantum Mechanics. The entire discussion will be held under the name “Quantum Theory”. Theory that tries to analyze and describe the behavior of physical systems of reduced dimensions, close to the sizes of molecules, atoms and subatomic particles. We hope that the reader will appreciate the genius of these two titans in this field of Physics when they magnificently formulate the arguments that support the object of their defenses.
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.
The objective of this article is to demonstrate how the historical debate between materialism and idealism, in the field of Philosophy, extends, in new clothes, to the field of Quantum Physics characterized by realism and anti-realism. For this, we opted for a debate, also historical, between the realism of Albert Einstein, for whom reality exists regardless of the existence of the knowing subject, and Niels Bohr, for whom we do not have access to the ultimate reality of the matter, unless conditioning it to the existence of an observer endowed with rationality, position adopted in the Interpretation of Complementarity (1927) – posture that was expanded in 1935 when Bohr assumed a “relationalist” conception, according to which the quantum state is defined by the relationship between the quantum object and the entire measuring device. This is an extremely important debate, as it further consolidates the results of nascent Quantum Mechanics, guaranteeing Bohr the leadership of the orthodoxy based on the interpretation of complementarity. Here, when dealing with Quantum Theory, we will not make any distinction between the terms Quantum Physics, Quantum Theory or Quantum Mechanics. The entire discussion will be held under the name “Quantum Theory”. Theory that tries to analyze and describe the behavior of physical systems of reduced dimensions, close to the sizes of molecules, atoms and subatomic particles. We hope that the reader will appreciate the genius of these two titans in this field of Physics when they magnificently formulate the arguments that support the object of their defenses.