The chapter discusses Bohr’s response to the famous Einstein-Podolsky-Rosen criticism of quantum mechanics, illuminating the clash between Bohr’s approach, firmly grounded in the existing experimental context, and Einstein’s prescient philosophical concerns. Given its accord with Ernst Mach’s influential double-aspect philosophical view, Bohr’s broader philosophical argument reads as a conventional piece of philosophical thought aimed at further clarifying the account already produced by the inductive process.
The chapter discusses Bohr’s response to the famous Einstein-Podolsky-Rosen criticism of quantum mechanics, illuminating the clash between Bohr’s approach, firmly grounded in the existing experimental context, and Einstein’s prescient philosophical concerns. Given its accord with Ernst Mach’s influential double-aspect philosophical view, Bohr’s broader philosophical argument reads as a conventional piece of philosophical thought aimed at further clarifying the account already produced by the inductive process.
ASPECTS OF THE DEBATE The debate between Niels Bohr and Albert Einstein concerning the interpretation of quantum mechanics extended from the fifth Solvay Conference in 1927 until the end of Einstein's life. The most dramatic exchange occurred in 1935, when Einstein, in collaboration with B. Podolsky and N. Rosen, published a paper in Physical Review entitled “Can quantum-mechanical description of physical reality be considered complete?”, concluding with a negative answer, and Bohr replied in the same journal, with a paper of the same title but giving a positive answer. Their arguments were restated, in some respects with greater clarity, in the Library of Living Philosophers volume on Einstein in 1949. The disagreements between Bohr and Einstein concerned not only the physical question expressed in the common title of their papers, but also philosophical questions about physical reality and human knowledge. Much light was thrown upon the Bohr–Einstein debate by the theorem of J. S. Bell (1964) and the experiments which it inspired. Bell showed that any physical theory which applies to a pair of spatially separated systems (as considered in the thought experiment of Einstein, Podolsky, and Rosen) and satisfies a certain locality condition will, in certain circumstances, disagree statistically with quantum mechanics. Consequently, the supplementation of the quantum mechanical description envisaged by Einstein and his collaborators (usually referred to as a “hidden variables theory”) must either violate the locality condition or clash with quantum mechanical predictions.
Niels Bohr was born on October 7, 1885. He was one of the great innovators in physical science in the twentieth century. It so happens that 1985 also marks fifty years since the long discussions, which had begun in the 1920s between Albert Einstein and Bohr on the philosophical problems of quantum physics, attained their apogee. An article co-authored by Einstein, B. Podolsky, and N. Rosen, "Can Quantum Mechanics Be Considered a Complete Description of Physical Reality?,"1 was published in 1935 in the journal Physical Review. According to Bohr, "by virtue of its clarity and, it would seem, flawless argumentation, the work of Einstein, Podolsky, and Rosen has created excitement among physicists and played a great role in the discussion of general philosophical questions of physics."2 Precisely as a result of the publication of this article, the critical position of Einstein concerning quantum mechanics became known to a broader circle of physicists. (Prior to this not many physicists had participated in the discussions.)3 In the same year, Bohr responded to Einstein and his co-authors with an article under the same title.4
Ever since it first appeared in 1935, the famous paper by Einstein, Podolsky and Rosen, questioning the completeness of quantum mechanics as a theory, has courted controversy. The initial arguments with Bohr have never been forgotten or gone away; the ideas of Bell have remained; many experiments have been performed purporting to support the stance of Bohr. More recently, however, an experiment performed by a group in Basel has questioned this accepted position and, theoretically, this new perspective has received support from at least two sources. It is the work behind these two sources, especially the second, together with the experimental work at Basel, which form the basis for this examination of the present position as far as this extremely important position for physical science is concerned. Needless to say, considering the views expressed in these two approaches, it is also necessary and appropriate to consider some possible consequences if this new view becomes accepted. Due to the fact that the recent support for the Einstein, Podolsky, Rosen argument makes use of results in iso-mathematics, iso-mechanics and iso-chemistry, these possible consequences include the exact representation of nuclear data, the achievement of an attractive force between identical valence electrons with the ensuing exact representation of molecular data, the prediction of new clean energies and the prediction of the possible recycling of nuclear waste via stimulated decay—none of which is allowable utilising traditional quantum mechanics. Hence here, as well as discussing the resolution of the long standing issue provoked by the well-known Einstein, Podolsky, Rosen article, some of these consequences will be discussed with a view to provoking more general, open-minded discussion within the scientific community.
The 1935 debate opposing Einstein, Podolsky and Rosen to Bohr elicited so many comments and developments, both theoretical and experimental, until this day, that the main point at stake at that time can be overlooked by modern readers, especially students. This paper draws the reader's attention to the historical background of Einstein's paper and Bohr's reply. We show that Einstein's definition of a complete physical theory is taken from Mach's criticism of atomic theory based upon classical-mechanical views. As for Bohr's definition of physical reality, it can be simply understood by reference to classical physics although it was embedded in the quantum-mechanical formalism.
Assessment of Einstein's argument Is quantum mechanics complete and local … It was observed in §1.4 that Einstein's method of criticizing the orthodox view of quantum theory was to focus on examples whose special characteristics could be used to show that adherence to the completeness assumption compels one to adopt ‘unnatural theoretical interpretations’. It was a way not of disproving the conventional interpretation by attempting to locate in it some logical flaw, but of pushing it into a corner that in Einstein's view no one would seriously want to inhabit. The paper of Einstein, Podolsky & Rosen (EPR) (1935) is the most famous component of this programme and the purpose of this chapter is to analyse the extent to which the arguments presented in it are compatible with the quantum theory of motion. From contemporaneous correspondence it appears that the EPR paper was written by Podolsky and that Einstein did not consider that the point which was really troubling him had been made explicit (Fine, 1986, Chap. 3). According to Einstein's accounts, EPR had the following purpose: to show that if one believes the wavefunction exhausts all the statements that can be meaningfully asserted about a physical system, then one must also accept that the real physical state of the system depends on what befalls another system with which it has previously interacted, no matter how far apart the two systems may become.