Quantum mechanics has seemed to defy all attempts to construe it realistically, but antirealism, like the many‐worlds hypothesis, is even more difficult to accept. In order to give a realist construal of quantum mechanics, we need first to distinguish the objective and rational aspect of reality from the paradigmatic thing‐like aspects of having determinate physical properties: quantum‐mechanical entities may be real in the former sense though not in the latter. Anti‐realist arguments are based on the difficulty of giving an account of quantum‐mechanical collapse and the apparent superluminal velocities involved. Objections to superluminal velocities on the score of the special theory of relativity are found not to be conclusive, and the price—there being some preferred frame of reference—to be acceptable. A sketch of a probabilistic account of quantum‐mechanical collapse is offered, which makes the difference between the macro‐ and the micro‐world a matter of degree rather than kind. If that, or some other, account proved acceptable, we could be quantum‐mechanical realists, though quantum‐mechanical reality would be very different from that of material objects in hardware shops.
Quantum mechanics has seemed to defy all attempts to construe it realistically, but antirealism, like the many‐worlds hypothesis, is even more difficult to accept. In order to give a realist construal of quantum mechanics, we need first to distinguish the objective and rational aspect of reality from the paradigmatic thing‐like aspects of having determinate physical properties: quantum‐mechanical entities may be real in the former sense though not in the latter. Anti‐realist arguments are based on the difficulty of giving an account of quantum‐mechanical collapse and the apparent superluminal velocities involved. Objections to superluminal velocities on the score of the special theory of relativity are found not to be conclusive, and the price—there being some preferred frame of reference—to be acceptable. A sketch of a probabilistic account of quantum‐mechanical collapse is offered, which makes the difference between the macro‐ and the micro‐world a matter of degree rather than kind. If that, or some other, account proved acceptable, we could be quantum‐mechanical realists, though quantum‐mechanical reality would be very different from that of material objects in hardware shops.
Quantum mechanics has always presented a problem for scientific realists. For it does not seem to offer a coherent picture of the world. I think it does, and that there is a viable quantum mechanical model of reality. But it cannot be constructed, given the continuity constraints that we usually place on realistic models. To be a quantum mechanical realist, one has to be willing to accept that there are two fundamentally different kinds of processes occurring in nature: continuous, but quantum mechanically indeterminate, energy transfer processes and discontinuous, but spatially extended, changes of state. The unwillingness of philosophers to accept that there is such a distinction has caused many of them to doubt the reality of Schrödinger waves, and the processes of their generation and collapse. I am fully aware that I am treading on well-trodden territory, and that the technical difficulties that must be faced by anyone who is not a specialist in the field are immense. Nevertheless, I think there is a fairly clear metaphysical position on these issues derivable from the kind of essentialist realism outlined in the previous chapter, and I ask readers to bear with me. First, realism about Schrödinger waves requires the belief that particles are always transmitted as quantum mechanically indeterminate waves, but always act as classically determinate particles on whatever absorbs them. The probability of absorption by a given absorbing object (e.g. measuring instrument) at a given location is determined by the value of the Ψ-function at this point.
Quantum mechanics has always presented a problem for scientific realists.For it does not seem to offer a coherent picture of the world.I think it does, and that there is a viable quantum mechanical model of reality.But it cannot be constructed, given the continuity constraints that we usually place on realistic models.To be a quantum mechanical realist, one has to be willing to accept that there are two fundamentally different kinds of processes occurring in nature: continuous, but quantum mechanically indeterminate, energy transfer processes and discontinuous, but spatially extended, changes of state.The unwillingness of philosophers to accept that there is such a distinction has caused many of them to doubt the reality of Schrodinger waves, and the processes of their generation and collapse.I am fully aware that I am treading on well-trodden territory, and that the technical difficulties that must be faced by anyone who is not a specialist in the field are immense.Nevertheless, I think there is a fairly clear metaphysical position on these issues derivable from the kind of essentialist realism outlined in the previous chapter, and I ask readers to bear with me.First, realism about Schrodinger waves requires the belief that particles are always transmitted as quantum mechanically indeterminate 1.
Scientific realism has traditionally maintained that our best scientific theories can be regarded as more or less true and as representing the world as it is (more or less). However, one of our very best current theories—quantum mechanics—has famously resisted such a realist construal, threatening to undermine the realist stance altogether. The chapters in this volume carefully examine this tension and the reasons behind it, including the underdetermination generated by the multiplicity of formulations and interpretations of quantum physics, each presenting a different way the world could be. Authors in this volume offer a range of alternative ways forward: some suggest new articulations of realism, limiting our commitments in one way or another; others attempt to articulate a ‘third way’ between traditional forms of realism and antirealism, or are critical of such attempts. Still others argue that quantum theory itself should be reconceptualised, or at least alternative formulations should be considered in the hope of evading the problems faced by realism. And some examine the nature of these issues when moving beyond quantum mechanics to quantum field theory. Taken together they offer an exciting new set of perspectives on one of the most fundamental questions in the philosophy of modern physics: how can one be a realist about quantum theory, and what does this realism amount to?
The framework of a simple opposition realism – anti-realism is not enough to analyze the views on the reality of unobservable objects of quantum theory. First, it is necessary to distinguish between realism in relation to the theory and realism in relation to the theory’s objects. Secondly, realism in relation to classical objects can be combined, both with realism and with anti-realism in relation to quantum objects. Third, the concept of “existence” and “to exist objectively” can have different meanings. To take into account these factors, the article describes three approaches: classical realism, quantum anti-realism, and quantum realism. I show that the debate around quantum reality has intensified in recent decades due to a series of new quantum experiments. The current stage of the debate is caused by the second quantum revolution relating to the transfer and processing of quantum information. Classical realism and old versions of quantum anti-realism have become insufficiently effective to explain the results of a series of experiments. Proponents of quantum realism, in turn, refer to the possibility of using the wave function to manipulate quantum objects before their measurement. In conclusion, I assume that not only theoretical discussions but also experiments and new technologies can have a major impact on the seemingly purely philosophical debate about reality.
According to scientific realism, science gives us an approximately true description of what the world is like. But what does it mean? In this chapter, we focus on the ontological and metaphysical aspects of this discussion. That is, we are concerned with the following questions: what there is, according to our best scientific theories? And how are these things that theories say exist? We start from the assumption that a genuine scientific realism must deal with these issues. Taking non-relativistic quantum mechanics as a case study, we discuss some of the challenges currently faced by a genuinely realistic stance. We argue, first, that in the ontological aspect, realists are in the same boat as science, that is, without sufficient epistemic justification to adopt the belief in the entities postulated by a single quantum theory, given that experience (currently) is not able to decide between rival theories; in the metaphysical aspect, realists also encounter problems with theory choice, given the possibility of associating more than one metaphysical theory with the description of the entities postulated by each quantum theory. The same goes for structuralist alternatives, since, even if we accept that scientific theories are committed to the existence of structures, but not objects, we still do not know what structures are, metaphysically. Finally, we move forward in the discussion with the meta-Popperian method, which serves to reduce the metaphysical alternatives associated with the ontological postulates of scientific theories. We may not know what the correct alternative is, but we have been able to progressively check which metaphysical alternatives are incompatible with each scientific theory.
This chapter provides a moderately precise shape to the idea that physical reality is independent of physicists, an idea deeply rooted in the minds of scientists and laymen alike. This idea is particularized through the introduction of supplementary assumptions that are inspired by common sense. The versions of realism thus obtained are discussed in the light of quantum physics. They are found to be unacceptable. In order for realism to be something more than an arbitrary metaphysical construction, physicists should have some grip on reality through their experience. In conventional quantum mechanics, the hypothesis implies that at any time in its history a microscopic particle always possesses a complete set of compatible observables endowed with definite values. Macro-objectivism, in spite of physicists' reference to experience, is distinctly a realistic philosophy, since it assumes that physical objects would exist and have specific properties even if no human beings existed.