Bohrs Relational Holism and the classical-quantum Interaction

📝 Abstract

In this paper I present and critically discuss the main strategies that Bohr used and could have used to fend off the charge that his interpretation does not provide a clear-cut distinction between the classical and the quantum domain. In particular, in the first part of the paper I reassess the main arguments used by Bohr to advocate the indispensability of a classical framework to refer to quantum phenomena. In this respect, by using a distinction coming from an apparently unrelated philosophical corner, we could say that Bohr is not a revisionist philosopher of physics but rather a descriptivist one in the sense of Strawson. I will then go on discussing the nature of the holistic link between classical measurement apparatuses and observed system that he also advocated. The oft-repeated conclusion that Bohr’s interpretation of the quantum formalism is untenable can only be established by giving his arguments as much force as possible, which is what I will try to do in the following by remaining as faithful as possible to his published work.

💡 Analysis

In this paper I present and critically discuss the main strategies that Bohr used and could have used to fend off the charge that his interpretation does not provide a clear-cut distinction between the classical and the quantum domain. In particular, in the first part of the paper I reassess the main arguments used by Bohr to advocate the indispensability of a classical framework to refer to quantum phenomena. In this respect, by using a distinction coming from an apparently unrelated philosophical corner, we could say that Bohr is not a revisionist philosopher of physics but rather a descriptivist one in the sense of Strawson. I will then go on discussing the nature of the holistic link between classical measurement apparatuses and observed system that he also advocated. The oft-repeated conclusion that Bohr’s interpretation of the quantum formalism is untenable can only be established by giving his arguments as much force as possible, which is what I will try to do in the following by remaining as faithful as possible to his published work.

📄 Content

1 Bohr’s Relational Holism and the classical-quantum Interaction1

Mauro Dorato Department of Philosophy Communication and Media Studies University of Rome “Roma Tre”,
Via Ostiense 234, 00144, Rome, Italy dorato@uniroma3.it

1 Introduction: a conflict in Bohr’s philosophy?

Bohr’s philosophy of quantum mechanics has often been charged for what is allegedly one of its major shortcomings, namely the advocacy of an unambiguous classical/quantum distinction (let me refer to this view with the label the distinction thesis). As is well known, such a distinction is needed to defend Bohr’s view that any communicable measurement outcome must presuppose a classically describable instrument, with respect to which any reference to the quantum of action can be neglected (Bohr 1958, 4). Critics have then often insisted on the fact that the distinction in question is hopelessly vague (Bell 1987, 29) or at least strongly contextual (Ghirardi 2004), so that Bohr’s interpretation of quantum mechanics suffers from the same vagueness and adhoc-ness. The resulting problem is, allegedly, a renunciation to describe the dynamical interaction between system and apparatus in a physically precise, theoretically based and non-contextual way, and therefore to offer a much-needed solution to the measurement problem.
In my paper I will present and critically discuss the main strategies that Bohr used and could have used to defend from this charge his interpretation of quantum mechanics. In particular, in the first part I will reassess the main arguments that Bohr used to advocate the

1 Thanks to Henry Folse and Jan Faye for their attentive reading of a previous draft of the paper.

2 indispensability of a classical framework to refer to quantum phenomena by trying to look at them from a new angle. I will then go on to discussing the nature of the indispensible link between classical measurement apparatuses and observed system that he also advocated. Typically, this link has been interpreted as a mere neopositivistic appeal to the fact that it is meaningless to talk about state-dependent properties of quantum entities independently of a measurement apparatus (Redhead 1987, 49-51, and Beller and Fine 1994). On the contrary, other authoritative scholars have rejected this minimalistic reading by stressing the fact that Bohr’s view implies the presence of a holistic nonseparability between quantum system and classical apparatuses (Bohm 1951, Folse 1985, Faye 1991, Whitaker 2004, 1324). Howard (2004) and Tanona (2004, 691) explicitly interpret Bohr’s relational view of a measurement by invoking the notion of entanglement. And it is clear that in this latter case, Bohr should have offered an explicit and well-articulated theory of measurement, a challenge that has been accepted among others also by Zinkernagel (2016) who, by relying on Landau and Litshitz’s brief treatment (1981, 2-26), insisted that the quantum system interacts with only a part of a classical apparatus. In order to evaluate this discussion and give due emphasis to Bohr’s holistic understanding of a quantum “phenomenon” (Bohr 1935 and 1958 among other sources), it is important to distinguish among different senses of Bohr’s “holism” and consider which of these can be reconciled with “the distinction thesis” that he also explicitly advocated.
Let me add at the outset that in the following I will not try to argue that Bohr’s interpretation of quantum mechanics is free from any conceptual difficulties. Nevertheless, I will try to correct some frequent misunderstandings that many of his critics have fallen prey to. After the 1935 confrontation with Einstein, it is well known that philosophers and physicists attributed to Bohr a definite victory over Einstein’s criticism. But since the late sixties’ surge of interest in the foundations of physics caused by Bell’s theorem and his sympathy for alternative

3 formulations of quantum mechanics (Bohmian mechanics and dynamical reduction models), Bohr has become been regarded as responsible – and not just by philosophers – for having “brainwashed a whole generation of physicists into thinking that the job was done 50 years ago” (Gell-Mann 1976, 29). It is about time to achieve a more balanced picture of Bohr’s contribution to the philosophy of quantum mechanics. The conclusion that Bohr’s interpretation of the formalism is untenable can only be established by giving his arguments as much force as possible, which is what I will try to do in the following by remaining as faithful as possible to his published work.

2 Bohr’s recourse to classical concepts

Various misunderstandings of Bohr’s philosophy of quantum mechanics have certainly been favored by the obscurities of his prose that he himself later acknowledged (Bohr 1949, 233),2 as well as by overly polemical remarks due to some his brilliant opponents. Here is one

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