The main ambition of this work has been to explore the prospects for dissolving the foundational problems of quantum theory by adopting the epistemic conception of quantum states and reflecting on how it should be spelled out in detail. This differs (at least in emphasis, if not more profoundly) from the main ambition of those — ‘realistically minded’ — philosophers whose declared aim is to determine what reality is like if it is as quantum theory says. If the Rule Perspective is correct, quantum theory does not really say anything about reality at all: features of reality are described not by quantum states, but by NQMCs, and while quantum theory helps us ascribe probabilities to the NQMCs, it does not typically make any statements as to which NQMCs are true and which are false. However, even though quantum theory does not in that sense say anything about reality, we can learn a lot about reality by reflecting on what features it must have for quantum theory’s undisputed empirical success to be possible. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
The main ambition of this work has been to explore the prospects for dissolving the foundational problems of quantum theory by adopting the epistemic conception of quantum states and reflecting on how it should be spelled out in detail. This differs (at least in emphasis, if not more profoundly) from the main ambition of those — ‘realistically minded’ — philosophers whose declared aim is to determine what reality is like if it is as quantum theory says. If the Rule Perspective is correct, quantum theory does not really say anything about reality at all: features of reality are described not by quantum states, but by NQMCs, and while quantum theory helps us ascribe probabilities to the NQMCs, it does not typically make any statements as to which NQMCs are true and which are false. However, even though quantum theory does not in that sense say anything about reality, we can learn a lot about reality by reflecting on what features it must have for quantum theory’s undisputed empirical success to be possible. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
An outline is given of the interpretation of quantum mechanical expressions if one assumes that what is called Quantum Mechanics today, refers to an underlying reality as in Chap. 2 , even if many authors claim to have evidence to the contrary, as is usually brought forward. If there exists a sub-microscopic classical world of real things, is that the same classical world as the world of large things such as planets, rocks and people? How does the notion of probability enter into quantum mechanics? These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Introduction We saw in Part I that in addition to explaining consciousness there is another hard problem for the modern scientific worldview – understanding what quantum physics is telling us about reality. And if anything this one is harder. In philosophy of mind there is at least consensus enough for an orthodox position to exist (materialism), and a widespread expectation that it will be vindicated by future neuroscience. By contrast, in philosophy of physics all sides understand that quantum theory is compatible with a variety of metaphysical interpretations, and have little hope that new empirical discoveries will settle the matter. But both problems are “hard” in the sense that, despite tremendous intellectual effort over many decades, no clear progress has been made toward solving them. The basic idea of quantum consciousness theory is that bringing the two problems into contact may be the key to solving both (though I will be addressing only the mind–body problem in what follows). That this could be a novel idea attests to the fact that their philosophical discussions have evolved quite separately. While philosophers of physics have long been interested in the role of consciousness in the measurement process, they have engaged little with the mind–body problem per se; and philosophers of mind have been almost unanimous in dismissing the suggestion that consciousness has anything interesting to do with quantum physics. Social scientists might echo such skepticism, wondering how adding the problem of interpreting quantum theory to the problem of consciousness will help them . Besides piling up jargon and arcane debates, in moving to the sub-atomic level we are now even farther removed from the human world, and seemingly poised to engage in the most vulgar reductionism. Yet, naïvely one might expect the two problems to be related, for two reasons. The first is the intriguing analogies mentioned in Chapter 1 between the mental and quantum domains.
The previous chapter addressed the challenge of making sense of the notion of a quantum state assignment being performed correctly without thereby acknowledging the notion of a quantum state a quantum system ‘is in’. The present chapter discusses what interpretation of quantum probabilities goes best with the account that I have called the ‘Rule Perspective’ and started to develop in the previous chapter. The first section considers what quantum probabilities should be taken to be probabilities of in the Rule Perspective; the second investigates what philosophical interpretation of probabilities applies best to quantum probabilities thus conceived. The third section considers two objections to the resulting account of quantum probabilities. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Abstract Quantum theory provides a superb description of physical reality on a small scale, yet it contains many mysteries. Without doubt, it is hard to come to terms with the workings of this theory, and it is particularly difficult to make sense of the kind of ‘physical reality’—or lack of it—that it seems to imply for our world. Taken at its face value, the theory seems to lead to a philosophical standpoint that many (including myself) find deeply unsatisfying. At best, and taking its descriptions at their most literal, it provides us with a very strange view of the world indeed. At worst, and taking literally the proclamations of some of its most famous protagonists, it provides us with no view of the world at all.
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?
A quantum state, via the Born Rule, assigns probabilities to the different possible values of observables of a quantum system. It is only in virtue of these probabilities — or, alternatively, expectation values — that quantum mechanics is empirically testable. Since assigning a state to a system means assigning probabilities to the values of observables, it may seem natural to read Peierls’ claim that the state ‘represents our knowledge of the system’ (Peierls [1991], p. 19) as a shorthand for saying that the state represents our knowledge of these probabilities. The latter view is sometimes even straightforwardly identified with the epistemic conception of states, for example by Marchildon, who claims that ‘[i]n the epistemic view [of quantum states], the state vector (or wave function or density matrix) does not represent the objective state of a microscopic system […], but rather our knowledge of the probabilities of outcomes of future measurements’ (Marchildon [2004], p. 1454). However, according to an argument due to Fuchs and endorsed by Timpson, 31 the idea that quantum states represent our knowledge about quantum probabilities should not be regarded as the core claim of the epistemic conception of quantum states, simply because, as they argue, this idea is in fact incompatible with the latter. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.