Quantum dynamical reduction and reality: Replacing probability densities with densities in real space

Consideration is given to recent attempts to solve the objectification problem of quantum mechanics by considering nonlinear and stochastic modifications of Schrödinger's evolution equation. Such theories agree with all predictions of standard quantum mechanics concerning microsystems but forbid the occurrence of superpositions of macroscopically different states. It is shown that the appropriate interpretation for such theories is obtained by replacing the probability densities of standard quantum mechanics with mass densities in real space. Criteria allowing a precise characterization of the idea of similarity and difference of macroscopic situations are presented and it is shown how they lead to a theoretical picture which is fully compatible with a macrorealistic position about natural phenomena.     

Schrödinger's Cat and Divine Action: Some Comments on the Use of Quantum Uncertainty to Allow for God's Action in the World

I present results of recent work in the field of quantum optics and relate this work to discussions about the theory of quantum mechanics and God's divine action in the world. Experiments involving atomic decay, relevant to event uncertainty in quantum mechanics, as well as experiments aimed at elucidating the so–called Schrödinger's–cat paradox, help clarify apparent ambiguities or paradoxes that I believe are at the heart of renewed attempts to locate God within our constructed physical theories and tend to narrow the gaps proposed as an opening for divine action. Some problems arise because of imprecise use of nonmathematical language to force quantum mechanics into an intuitive "classical" framework.     

Refutability Revamped: How Quantum Mechanics Saves the Phenomena

On the basis of the Suppes–Sneed structuralview of scientific theories, we take a freshlook at the concept of refutability,which was famously proposed by K.R. Popper in 1934 as a criterion for the demarcation of scientific theories from non-scientific ones, e.g., pseudo-scientificand metaphysical theories. By way of an introduction we argue that a clash between Popper and his critics on whether scientific theories are, in fact, refutablecan be partly explained by the fact Popper and his criticsascribed different meanings to the term theoryThen we narrow our attention to one particular theory,namely quantum mechanics, in order to elucidate general matters discussed. We prove that quantum mechanics is irrefutable in a rather straightforward sense, but argue that it is refutable in a more sophisticated sense, which incorporates someobservations obtained by looking closely at the practiceof physics. We shall locate exactly where non-rigourous elements enter the evaluation of a scientific theory – thismakes us see clearly how fruitful mathematics isfor the philosophy of science.     

Some problems concerning language and physics

We discuss three problems concerning the use of formal languages in theoretical physics: (i) the definability of time and spacetime in classical physical theories; (ii) how to cope with indistinguishable elementary particles in quantum mechanics without labeling them; and (iii) how to get a formal picture of quantum states jumping.     

Why did the new physics force out the old?

The aim of my paper is to demonstrate that Special Relativity and the early quantum theory were created within the same programme of statistical mechanics, thermodynamics and Maxwellian electrodynamics. I shall try to explain why classical mechanics and classical electrodynamics were “refuted” almost simultaneously or, in other words, why the quantum revolution and the relativistic one both took place at the beginning of the 20th century. I shall argue that the quantum and relativistic revolutions were simultaneous since they had a common origin—the clash between the fundamental theories of the second half of the 19th century that constituted the “body” of classical physics. The revolution's most dramatic point was Einstein's 1905 photon paper that laid the foundations of both special relativity and the old quantum theory. Hence the dialectic of the old theories is crucial for theory change. Later, classical physics was forced out by the joint development of quantum and relativistic sub‐programmes. The title of my paper can be reformulated in Bruno Latour's terms: The Einstein Revolution or Drawing Models Together.     

A Quantum-Mechanical Argument for Mind–Body Dualism

I argue that a strong mind–body dualism is required of any formulation of quantum mechanics that satisfies a relatively weak set of explanatory constraints. Dropping one or more of these constraints may allow one to avoid the commitment to a mind–body dualism but may also require a commitment to a physical–physical dualism that is at least as objectionable. Ultimately, it is the preferred basis problem that pushes both collapse and no-collapse theories in the direction of a strong dualism in resolving the quantum measurement problem. Addressing this problem illustrates how the construction and evaluation of explanatorily rich physical theories are inextricably tied to the evaluation of traditional philosophical issues.     

Measurement and the interpretation of quantum mechanics and relativity theory

The axiomatic approaches of quantum mechanics and relativity theory are compared with approaches in which the theories are thought to describe readings of certain measurement operations. The usual axioms are shown to correspond with classes of ideal measurements. The necessity is discussed of generalizing the formalisms of both quantum mechanics and relativity theory so as to encompass more realistic nonideal measurements. It is argued that this generalization favours an empiricist interpretation of the mathematical formalisms over a realist one.     

The classical limit of quantum theory

Both physicists and philosophers claim that quantum mechanics reduces to classical mechanics as 0, that classical mechanics is a limiting case of quantum mechanics. If so, several formal and non-formal conditions must be satisfied. These conditions are satisfied in a reduction using the Wigner transformation to map quantum mechanics onto the classical phase plane. This reduction does not, however, assist in providing an adequate metaphysical interpretation of quantum theory.Earlier versions of this essay received helpful criticism from Bruce Knight, Clark Glymour, and Donald Martin.     

The Status of our Ordinary Three Dimensions in a Quantum Universe 1

There are now several, realist versions of quantum mechanics on offer. On their most straightforward, ontological interpretation, these theories require the existence of an object, the wavefunction, which inhabits an extremely high‐dimensional space known as configuration space. This raises the question of how the ordinary three‐dimensional space of our acquaintance fits into the ontology of quantum mechanics. Recently, two strategies to address this question have emerged. First, Tim Maudlin, Valia Allori, and her collaborators argue that what I have just called the ‘most straightforward’ interpretation of quantum mechanics is not the correct one. Rather, the correct interpretation of realist quantum mechanics has it describing the world as containing objects that inhabit the ordinary three‐dimensional space of our manifest image. By contrast, David Albert and Barry Loewer maintain the straightforward, wavefunction ontology of quantum mechanics, but attempt to show how ordinary, three‐dimensional space may in a sense be contained within the high‐dimensional configuration space the wavefunction inhabits. This paper critically examines these attempts to locate the ordinary, three‐dimensional space of our manifest image “within” the ontology of quantum mechanics. I argue that we can recover most of our manifest image, even if we cannot recover our familiar three‐dimensional space.     

On quantum entanglement,counterfactuals, causality and dispositions

The existence of non-local correlations between outcomes of measurements in quantum entangled systems strongly suggests that we are dealing with some form of causation here. An assessment of this conjecture in the context of the collapse interpretation of quantum mechanics is the primary goal of this paper. Following the counterfactual approach to causation, I argue that the details of the underlying causal mechanism which could explain the non-local correlations in entangled states strongly depend on the adopted semantics for counterfactuals. Several relativistically-invariant interpretations of spatiotemporal counterfactual conditionals are discussed, and the corresponding causal stories describing interactions between parts of an entangled system are evaluated. It is observed that the most controversial feature of the postulated causal connections is not so much their non-local character as a peculiar type of circularity that affects them.

     

A consciousness-based quantum objective collapse model

Ever since the early days of quantum mechanics it has been suggested that consciousness could be linked to the collapse of the wave function. However, no detailed account of such an interplay is usually provided. In this paper we present an objective collapse model (a variation of the Continuous Spontaneous Location model) where the collapse operator depends on integrated information, which has been argued to measure consciousness. By doing so, we construct an empirically adequate scheme in which superpositions of conscious states are dynamically suppressed. Unlike other proposals in which “consciousness causes the collapse of the wave function,” our model is fully consistent with a materialistic view of the world and does not require the postulation of entities suspicious of laying outside of the quantum realm.

     

Divine Omniscience: Is God's Foreknowledge at Risk in the Context of Contemporary Science?

Abstract

Does quantum indeterminacy threaten the classical theological doctrine of divine omniscience? Certain popular interpretations of quantum physics have challenged conventional ways of thinking about time and space, being and becoming. Consequently, the traditional doctrine that God knows all things, including future contingent events, has recently come under debate. This paper explores how the way we think about time affects the way we think about God's relation to time. Theologians need to be careful when appropriating scientific theories in their theological reflections because interpretations of those theories often bring along unnecessary metaphysical presuppositions. Using an interpretation of special relativity that focuses on the Lorentz transformation, this paper shows that modern physics does not truly challenge the doctrine of divine foreknowledge. In fact, modern physical theories can actually deepen theological reflection on the classical doctrine of divine omniscience.     

Subjectivist – observing and objective – participant perspectives on the world: Kant,aquinas and quantum mechanics

Theological thinking is influenced by perspectives on the relation of scientific knowledge to reality. Two paradigms for understanding the nature of human knowledge are considered in relation to quantum mechanics: the subjective-observing perspective of Kant, and the objective-participant perspective of Thomas Aquinas. I discuss whether quantum mechanics necessarily implies a subject centered perspective on reality, and argue, with reference to d'Espagnat's notion of veiled reality, that quantum non-separability challenges this view. I then explore whether the objective-participant perspective of Thomas Aquinas provides a more fruitful context for understanding quantum mechanics. I discuss quantum measurement in terms of the transition from potentiality to actuality, and knowledge as the latent intelligibility of the world realized. However, the negative nature of our knowledge of quantum non-separability also challenges this perspective. Our theological thinking in response to quantum knowledge must therefore proceed tentatively, balancing a via positiva, with a via negativa.     

The scientific turn in metaphysics: a factualist approach

In a recent paper, Cumpa (Am Philos Q 51(4): 319–324, 2014) argues that a scientific turn in metaphysics requires the acceptance of a materialist criterion of fundamentality, according to which the most fundamental metaphysical category is the one that provides us with a reconciliation of the ordinary world and the physical universe. He concludes that the dominant category of substance cannot be the most fundamental category, for it does not satisfy this criterion of fundamentality. The most fundamental category is instead the category of fact. Although convincing, the defense of factualism over substantialism offered by Cumpa takes into account the case of classical physics without considering the physical universe of quantum mechanics. My aim in this paper is to offer a completion to Cumpa’s factualist approach. To achieve my aim, I show that substances cannot provide a satisfactory account of the relationship between the ordinary world and the physical universe even in the case of quantum mechanics, whereas a factualist approach does.

     

Quantum No-Go Theorems and Consciousness

Our conscious minds exist in the Universe, therefore they should be identified with physical states that are subject to physical laws. In classical theories of mind, the mental states are identified with brain states that satisfy the deterministic laws of classical mechanics. This approach, however, leads to insurmountable paradoxes such as epiphenomenal minds and illusionary free will. Alternatively, one may identify mental states with quantum states realized within the brain and try to resolve the above paradoxes using the standard Hilbert space formalism of quantum mechanics. In this essay, we first show that identification of mind states with quantum states within the brain is biologically feasible, and then elaborating on the mathematical proofs of two quantum mechanical no-go theorems, we explain why quantum theory might have profound implications for the scientific understanding of one’s mental states, self identity, beliefs and free will.     

Quantum Mechanics and Metaphysical Indeterminacy

There has been recent interest in formulating theories of non-representational indeterminacy. The aim of this paper is to clarify the relevance of quantum mechanics to this project. Quantum-mechanical examples of vague objects have been offered by various authors, displaying indeterminate identity, in the face of the famous Evans argument that such an idea is incoherent. It has also been suggested that the quantum-mechanical treatment of state-dependent properties exhibits metaphysical indeterminacy. In both cases it is important to consider the details of the metaphysical account and the way in which the quantum phenomenon is captured within it. Indeed if we adopt a familiar way of thinking about indeterminacy and apply it in a natural way to quantum mechanics, we run into illuminating difficulties and see that the case is far less straightforward than might be hoped.