According to one possible diagnosis of the quantum measurement problem, it is a consequence of quantum fundamentalism claiming that ontology and epistemology of the world are exclusively quantum, and classical physics is only an approximation. For N. Bohr, the measurement problem is a pseudo-problem because any quantum phenomenon presupposes the classical context of an experimental setup and the use of classical concepts to describe it. We consider Bohr's position from the point of view of our contextual quantum realism (CQR), inspired by the later Wittgenstein philosophy. Our approach is consistent with H. Zinkernagel's interpretation, according to which Bohr's position is not only epistemological anti-fundamentalism, but also ontological anti-fundamentalism.
According to one possible diagnosis of the quantum measurement problem, it is a consequence of quantum fundamentalism claiming that ontology and epistemology of the world are exclusively quantum, and classical physics is only an approximation. For N. Bohr, the measurement problem is a pseudo-problem because any quantum phenomenon presupposes the classical context of an experimental setup and the use of classical concepts to describe it. We consider Bohr's position from the point of view of our contextual quantum realism (CQR), inspired by the later Wittgenstein philosophy. Our approach is consistent with H. Zinkernagel's interpretation, according to which Bohr's position is not only epistemological anti-fundamentalism, but also ontological anti-fundamentalism.
For Bohr quantum mechanics is complete. It expresses all that can be said about the atomic world, which he regards as a newly discovered and separate ontological component of reality, operating at the Planck scale, and describable only with a separate physics, namely, quantum mechanics. The classical world, in contrast, represents its binary and symbiotic counterpart, which is also ontologically substantive, but operates according to 'classical concepts'. The different physics of each component indicates a different ontology, the classical one is accessible to us, as we are classical objects, where the Planck scale does not apply, while the other is not. The measurement problem cannot therefore be solved through the discovery of hidden variables as these are classical in nature and therefore ineffective in explaining the quantum world. The measurement problem is therefore not due to epistemological limitations but emerges directly from a 'two worlds' dualism. Bohr's Copenhagen interpretation has therefore been erroneously misunderstood as a positivist retreat rather than as a view of reality proposing an ontological structure which is dualistic. l then propose similarities between Bohr and a ‘two worlds’ view of Kant, where noumena is an ontology which is inherently unknowable as it is devoid of a priori agents, much as the quantum world is unknowable as it is devoid of Bohr's classical concepts. However, just as classical concepts in Bohr are crucial in constituting classical reality, a priori intuitions and concepts in Kant are crucial in constituting phenomena, which are real ontological objects and not just appearances. The noumenal and quantum realms are therefore both substantive, but impossible to investigate. The phenomenal and classical worlds are also substantive. They are where objects and therefore meaning condenses. They are therefore open to our investigations.
Niels Bohr, considered one of the fathers of quantum mechanics, formulated a complex interpretation \nof quantum mechanics that guided his understanding of quantum experiments. The contemporary dispute \nbetween realism and anti-realism, the two main approaches to the interpretation of quantum mechanics, \nis often based on different attitudes towards or even readings of Bohr. We propose that a better \nunderstanding of Bohr’s philosophical thought can contribute to the contemporary reconciliation of \nthese opposing philosophical views and thus to a better understanding of the quantum world. Unfortunately, \nin many contemporary interpretations, Bohr’s philosophical approach to quantum mechanics \nhas been misunderstood, re-interpreted or labelled as ambiguous. This is mostly due to the dispersion \nof Bohr’s complex and unique interpretation through different texts, never united in a single systematically \nconceptualized work. To comprehensively explain Bohr’s philosophical approach and his main \nphilosophical concepts, we consider the many similarities between Bohr’s and Husserl’s philosophical \napproach to science. Husserl developed his philosophical standpoint in a cultural context similar to \nBohr’s and shared Bohr’s objects of philosophical consideration as well as his approach to these objects. \nParallel reading of Bohr’s and Husserl’s texts reveals the closeness between Bohr’s ontological realism— \nepistemological anti-realism standpoint and Husserl’s phenomenological standpoint. This explains \ntheir similar views on the relationship between mathematical language, scientific method and Nature. \nWhile Bohr’s use of the term phenomenon is not equal to Husserl’s, Husserl’s rigorous philosophical \nexplanation of the term helps us to better understand Bohr’s use. Furthermore, the parallel reading \nfacilitates better understanding of one of Bohr’s main philosophical theses, often labelled as ambiguous \nand interpreted in different ways, that it is necessary to use classical concepts to describe quantum phenomena. \nWe claim that the thesis is connected with the advance of epistemological reconsideration of \nscience at the time of Bohr’s writing. Thus, Bohr considers some parts of argumentation as self-evident, \nwhile they are not evident to the contemporary reader. Husserl’s analysis of the relationship between science and the life-world offers a much-needed background for a comprehensive understanding of \nBohr’s thesis. The insight into the similarities between Bohr’s and Husserl’s philosophical approach \nto science and scientific phenomena enables a philosophically rigorous reading of Bohr’s texts; it can \neliminate some of the disagreements between realists and anti-realists and provide a firmer philosophical \nground for a dialog between them.
This work presents a historical-epistemological analysis of the foundations of quantum mechanics. From a philosophical point of view, the relationships between quantum mechanics and scientific realism are highlighted, as well as the influence of the neo-positivist philosophy of the first decades of the 20th century. The great significance of measurement in the context of quantum mechanics is underlined, as an essential element in providing a coherent description of reality moving from the microcosm to the macrocosm, as well as the role that the measurement apparatus and the consciousness of the observer assume during the act of measurement, the ontological problem, the problem of the objectification of the wave function and the problem of the definition of discernibility. This is followed by an overview of the most important alternative proposals to the standard interpretation (Copenhagen interpretation), with particular reference to hidden variable theories, and other alternatives to standard quantum mechanics that profoundly modify the vision of reality, such as the Everett’s many-worlds theory, the QBism, the unified holistic approach.
The field of interpretation of quantum mechanics emerged in an attempt to solve the measurement problem. This turned on the perception that Niels Bohr avoided addressing the measurement problem by taking an instrumentalist view of quantum mechanics. I argue that this view is mistaken and Bohr's interpretation of quantum mechanics is realist. Moreover, Bohr's interpretation, which is different from textbook quantum mechanics (which is due more to Von Neumann and Paul Dirac), succeeds in solving the measurement problem. While the claim that Bohr dissolves the measurement problem within the limits of the epistemological framework he assumes has been made by a few authors, rarely has the case been made that Bohr's project unambiguously and completely overcomes the measurement problem. I make the strong case that Bohr eliminated the measurement problem altogether. For this, I put forward two new postulates through which to make sense of Bohr's interpretation. The article thus seeks to single out Bohr's interpretation from the various views that go together under the umbrella of orthodox quantum mechanics, and which have been traditionally considered susceptible to the measurement problem. It shows that Bohr's interpretation should be classified along with those like hidden variable theories, collapse models, modal interpretations etc., which offer a solution to the measurement problem and are committed to a realist ontology.
The Copenhagen interpretation of quantum theory is investigated from a philosophical point of view. It is justified the opinion that the philosophical attitude the Copenhagen interpretation is based on is in principle inevitable for a real comprehension of quantum theory. This attitude is mainly related to epistemological arguments. However, the measurement problem often seems not to be treated clearly enough within the interpretation. By referring to the property of the necessity to use macroscopic measurement instruments obeying classical concepts it is made the attempt to solve the measurement problem. According to this consideration the indeterministic character of quantum theory seems to have its origin in a lack of knowledge and thus it appears in a similar but more principle way than in statistical mechanics. It is emphasized the ontological character of the uncertainty relation and the related non locality of quantum theory suggesting that the existence of a position space is not as fundamental as the assumptions of general quantum theory.
The spectacular successes of quantum physics have made it a commonplace to assert that we live in a quantum world. This idea seems to imply a kind of "quantum fundamentalism" according to which everything in the universe (if not the universe as a whole) is fundamentally of a quantum nature and ultimately describable in quantum-mechanical terms. Bohr's conception of quantum mechanics has traditionally been seen as opposed to such a view, not least because of his insistence on the necessity of the concepts of classical physics in the account of quantum phenomena. Recently, however, a consensus seems to be emerging among careful commentators on Bohr to the effect that he, after all, did subscribe to some version of quantum fundamentalism. Against this consensus, and by re-examining the historical record, I will defend a variant of the traditional reading of Bohr in which (1) the answer to what an object is (quantum or classical) depends on the experimental context; and (2) in principle, any physical system can be treated quantum-mechanically but not all systems can be treated that way at the same time.