Realism and Objectivism in Quantum Mechanics

The present study attempts to provide a consistent and coherent account of what the world could be like, given the conceptual framework and results of contemporary quantum theory. It is suggested that standard quantum mechanics can, and indeed should, be understood as a realist theory within its domain of application. It is pointed out, however, that a viable realist interpretation of quantum theory requires the abandonment or radical revision of the classical conception of physical reality and its traditional philosophical presuppositions. It is argued, in this direction, that the conceptualization of the nature of reality, as arising out of our most basic physical theory, calls for a kind of contextual realism. Within the domain of quantum mechanics, knowledge of ??reality in itself??, ??the real such as it truly is?? independent of the way it is contextualized, is impossible in principle. In this connection, the meaning of objectivity in quantum mechanics is analyzed, whilst the important question concerning the nature of quantum objects is explored.     

Quantum monism: an assessment

Monism is roughly the view that there is only one fundamental entity. One of the most powerful argument in its favor comes from quantum mechanics. Extant discussions of quantum monism are framed independently of any interpretation of the quantum theory. In contrast, this paper argues that matters of interpretation play a crucial role when assessing the viability of monism in the quantum realm. I consider four different interpretations: modal interpretations, Bohmian mechanics, many worlds interpretations, and wavefunction realism. In particular, I extensively argue for the following claim: several interpretations of QM do not support monism at a more serious scrutiny, or do so only with further problematic assumptions, or even support different versions of it.     

God's Action in the World: The Relevance of Quantum Mechanics

It has been suggested that God can act on the world by operating within the limits set by Heisenberg's uncertainty principle (HUP) without violating the laws of nature. This requires nature to be intrinsically indeterministic. However, according to the statistical interpretation the quantum mechanical wavefunction represents the average behavior of an ensemble of similar systems and not that of a single system. The HUP thus refers to a relation between the spreads of possible values of position and momentum and so is consistent with a fully deterministic world. This statistical interpretation of quantum mechanics is supported by reference to actual measurements, resolves the quantum paradoxes, and stimulates further research. If this interpretation is accepted, quantum mechanics is irrelevant to the question of God's action in the world.     

Are the Laws of Quantum Logic Laws of Nature?

The main goal of quantum logic is the bottom-up reconstruction of quantum mechanics in Hilbert space. Here we discuss the question whether quantum logic is an empirical structure or a priori valid. There are good reasons for both possibilities. First, with respect to the possibility of a rational reconstruction of quantum mechanics, quantum logic follows a priori from quantum ontology and can thus not be considered as a law of nature. Second, since quantum logic allows for a reconstruction of quantum mechanics, self-referential consistency requires that the empirical content of quantum mechanics must be compatible with the presupposed quantum ontology. Hence, quantum ontology contains empirical components that are also contained in quantum logic. Consequently, in this sense quantum logic is also a law of nature.     

Putnam on realism,reference and truth: The problem with quantum mechanics

In this essay, I offer a critical evaluation of Hilary Putnam's writings on epistemology and philosophy of science, in particular his engagement with interpretative problems in quantum mechanics. I trace the development of his thinking from the late 1960s when he adopted a strong causal-realist position on issues of meaning, reference, and truth, via the "internal realist" approach of his middle-period writings, to the various forms of pragmatist, naturalized, or "commonsense" epistemology proposed in his latest books. My contention is that Putnam's retreat from a full-fledged realist outlook has been prompted in large part by his belief that it cannot possibly be reconciled with the implications of quantum mechanics for our understanding of processes and events in the subatomic domain. However, I suggest, this response should be seen as premature given the range of as-yet unresolved problems with quantum mechanics on the orthodox (Copenhagen) interpretation and also the existence of an alternative account - David Bohm's hidden-variables theory - which perfectly matches the established predictive-observational results while providing a credible realist ontology. I also examine Putnam's case for adopting a nonstandard (three-valued) "quantum logic" in relation to the thinking of other philosophers - Michael Dummett among them - who have espoused a more global or doctrinaire version of anti-realism. I conclude that Putnam's early (causal-realist) position is by no means untenable in light of the various arguments that he now takes as counting decisively against it.     

Quantum Mechanics and the Plight of Physicalism

The literature on physicalism often fails to elucidate, I think, what the word physical in physicalism precisely means. Philosophers speak at times of an ideal set of fundamental physical facts, or they stipulate that physical means non-mental, such that all fundamental physical facts are fundamental facts pertaining to the non-mental. In this article, I will probe physicalism in the very much tangible framework of quantum mechanics. Although this theory, unlike “ideal physics” or some “final theory of non-mentality”, is an incomplete theory of the world, I believe this analysis will be of value, if for nothing else, at least for bringing some taste of physical reality, as it were, back to the debate. First, I will introduce a broad characterization of the physicalist credo. In Sect. 2, I will provide a rather quick review of quantum mechanics and some of its current interpretations. In Sect. 3, the notion of quantum non-separability will be analyzed, which will facilitate a discussion of the wave function ontology in Sect. 4. In Sects. 5 and 6, I will explore competing views on the implications of this ontology. In Sect. 7, I will argue that the prior results, based on a thoroughly realist interpretation of quantum mechanics, support only a weak version of non-reductive physicalism.     

Aspects in Dual‐Aspect Monism and Panpsychism: A Rejoinder to Benovsky

Neutral monism aims at solving the hard problem of consciousness by positing entities that are neither mental nor physical. Benovsky has recently argued for the slightly different account that, rather than being neutral, natural entities are both mental and physical by having different aspects, and then argued in favour of an anti‐realist interpretation of those aspects. In this essay, operating under the assumption of dual‐aspect monism, I argue to the contrary in favour of a realist interpretation of these aspects by showing that the anti‐realist interpretation collapses into neutral monism and that the realist interpretation is an interesting alternative. I close with a discussion of the realist interpretation of the aspects and its relation with panpsychism.     

What the Humean Should Say About Entanglement

Tim Maudlin has influentially argued that Humeanism about laws of nature stands in conflict with quantum mechanics. Specifically Humeanism implies the principle Separability: the complete physical state of a world is determined by the intrinsic physical state of each space‐time point. Maudlin argues Separability is violated by the entangled states posited by QM. We argue that Maudlin only establishes that a stronger principle, which we call Strong Separability, is in tension with QM. Separability is not in tension with QM. Moreover, while the Humean requires Separability to capture the core tenets of her view, there's no Humean‐specific motivation for accepting Strong Separability. We go on to give a Humean account of entangled states which satisfies Separability. The core idea is that certain quantum states depend upon the Humean mosaic in much the same way as the laws do. In fact, we offer a variant of the Best System account on which the systemization procedure that generates the laws also serves to ground these states. We show how this account works by applying it to the example of Bohmian Mechanics. The 3N‐dimensional configuration space, the world particle in it and the wave function on it are part of the best system of the Humean mosaic, which consists of N particles moving in 3‐dimensional space. We argue that this account is superior to the Humean account of Bohmian Mechanics defended by Loewer and Albert, which takes the 3N‐dimensional space, and its inhabitants, as fundamental.     

Wither away individuals

In this paper we deal with the problem of identity and individuality in quantum mechanics. We analyze three definitions of the concept of an individual and propose to check their merits in relation to the theory. In order to achieve our goals our approach also ties those definitions of individuality to two distinct kinds of naturalism in ontology: a strong version, according to which quantum mechanics must somehow authorize in a positive fashion the ontological concepts being dealt with, and a weak naturalism, according to which quantum mechanics must be only compatible with those ontological concepts. We conclude that strong naturalism is incompatible with the three concepts of individuality in quantum mechanics, and we argue that weak naturalism is not completely motivated, so that the best position to be assumed, in the end, is that the entities are simply not individuals. That is, in its craving to be compatible with strong naturalism, individuality ends up evaporating and we are left with non-individuals.     

The EPR-Experiment and Free Process Theory

As part of the ‘creation-discovery’ interpretation of quantum mechanics Diederik Aerts presented a setting with macroscopical coincidence experiments designed to exhibit significant conceptual analogies between portions of stuff and quantum compound entities in a singlet state in Einstein—Podolsky—Rosen/Bell-experiments (EPR-experiments). One important claim of the creation-discovery view is that the singlet state describes an entity that does not have a definite position in space and thus ‘does not exist in space’. ‘Free Process Theory’ is a recent proposal by Johanna Seibt of an integrated ontology, i.e., of an ontology suitable for the interpretation of theories of the macrophysical and microphysical domain (quantum field theory). The framework of free process theory allows us to show systematically the relevant analogies and disanalogies between Aerts' experiment and EPR-experiments. From free process ontology it also follows quite naturally that the quantum compound entity described by the singlet state ‘does not exist in space.’     

On Devitt’s Defence of Realism

In this paper I question the view that realism must delineate the basic ontological furniture of the world rather than giving arguments in semantic or epistemic terms for the existence of a mind-independent world. I call this view of stating and defending realism the Ontological Defence of Realism (or ODR) and take Devitt’s account of realism as a paradigmatic case of ODR. I argue that ODR cannot block ‘verificationist antirealism’ because the specific (physical) nature of what exists is not enough to secure the mind-independence of what exists and, additionally, every element purported to achieve this, it compromises seriously the idea that realism is primarily an ontological issue. I also stress that ODR is in tension with a plausible realist insight namely the priority of the world over our theorizing. Because of this tension ODR weakens realism in several domains with no good reason. Specifically, I argue that in these domains ODR faces a dilemma: either to reject realism or to take realism to be dependent on a reductive account violating the realist insight. My point is that we should keep realism and ontology distinct and that compliance with the realist insight initiates a better strategy for the defence of realism. I address three possible objections thereby further clarifying my point. I conclude by presenting my view about the relation between ontology and realism.     

Scientific Realism and Quantum Mechanics: Revisiting a Controversial Relation

The article examines the controversial relation of scientific realism with quantum mechanics. To this end, two distinct discussions are invoked: the discussion about ‘realism’ in the context of quantum mechanics and the discussion about ‘scientific realism’ in the context of the general philosophy of science. The aim is to distinguish them in order, first, to argue that the former—revolving around ‘local realism’ and the theorems of Bell and Kochen–Specker—unjustifiably identifies realism with features of a particular worldview, and thereby fosters the impression that the failure of ‘local realism’ in quantum experiments constitutes a failure of scientific realism too; and, second, in light of the latter discussion, to claim that scientific realism and quantum mechanics can be compatible—there is ground for dealing with quantum measurement simply as a physical mind-independent interaction. Therefore, a realist approach to the theory is possible despite its notorious measurement problem, even if the issue of its interpretation is still disputed.     

A modal ontology of properties for quantum mechanics

Our purpose in this paper is to delineate an ontology for quantum mechanics that results adequate to the formalism of the theory. We will restrict our aim to the search of an ontology that expresses the conceptual content of the recently proposed modal-Hamiltonian interpretation, according to which the domain referred to by non-relativistic quantum mechanics is an ontology of properties. The usual strategy in the literature has been to focus on only one of the interpretive problems of the theory and to design an interpretation to solve it, leaving aside the remaining difficulties. On the contrary, our aim in the present work is to formulate a “global” solution, according to which different problems can be adequately tackled in terms of a single ontology populated of properties, in which systems are bundles of properties. In particular, we will conceive indistinguishability between bundles as a relation derived from indistinguishability between properties, and we will show that states, when operating on combinations of indistinguishable bundles, act as if they were symmetric with no need of a symmetrization postulate.     

On the property structure of realist collapse interpretations of quantum mechanics and the so-called "counting anomaly"

The aim of this article is twofold. Recently, Lewis has presented an argument, now known as the "counting anomaly", that the spontaneous localization approach to quantum mechanics, suggested by Ghirardi, Rimini, and Weber, implies that arithmetic does not apply to ordinary macroscopic objects. I will take this argument as the starting point for a discussion of the property structure of realist collapse interpretations of quantum mechanics in general. At the end of this I present a proof of the fact that the composition principle, which holds true in standard quantum mechanics, fails in all realist collapse interpretations. On the basis of this result I reconsider the counting anomaly and show that what lies at the heart of the anomaly is the failure to appreciate the peculiarities of the property structure of such interpretations. Once this flaw is uncovered, the anomaly vanishes.     

Scientific Representation: Paradoxes of Perspective

David Lewis is a natural target for those who believe that findings in quantum physics threaten the tenability of traditional metaphysical reductionism. Such philosophers point to allegedly holistic entities they take both to be the subjects of some claims of quantum mechanics and to be incompatible with Lewisian metaphysics. According to one popular argument, the non-separability argument from quantum entanglement, any realist interpretation of quantum theory is straightforwardly inconsistent with the reductive conviction that the complete physical state of the world supervenes on the intrinsic properties of and spatio-temporal relations between its point-sized constituents. Here I defend Lewis's metaphysical doctrine, and traditional reductionism more generally, against this alleged threat from quantum holism. After presenting the non-separability argument from entanglement, I show that Bohmian mechanics, an interpretation of quantum mechanics explicitly recognized as a realist one by proponents of the non-separability argument, plausibly rejects a key premise of that argument. Another holistic worry for Humeanism persists, however, the trouble being the apparently holistic character of the Bohmian pilot wave. I present a Humean strategy for addressing the holistic threat from the pilot wave by drawing on resources from the Humean best system account of laws.     

An idealist critique of naturalism

ABSTRACT

According to many naturalists, our ordinary conception of the world is in tension with the scientific image: the conception of the world provided by the natural sciences. But in this paper, I present a critique of naturalism with precedents in the post-Kantian idealist tradition. I argue that, when we consider our actual linguistic behavior, there is no evidence that the truth of our ordinary judgments hinges on what the scientific image turns out to be like. I then argue that the best explanation of this result is that the norms and presuppositions operating in ordinary discourse are different from the norms and presuppositions operating in scientific discourse. So naturalistic attempts to undermine the manifest image are illegitimate attempts to critique a practice ‘from the outside’.     

Probability and objectivity in deterministic and indeterministic situations

This paper pursues the question, “To what extent does the propensity approach to probability contribute to plausible solutions to various anomalies which occur in quantum mechanics?” The position I shall defend is that of the three interpretations — the frequency, the subjective, and the propensity — only the third accommodates the possibility, in principle, of providing a realistic interpretation of ontic indeterminism. If these considerations are correct, then they lend support to Popper's contention that the propensity construction tends to remove (at least some of) the mystery from quantum phenomena.     

Wave Function Ontology

I argue that the wave function ontology for quantum mechanics is an undesirable ontology. This ontology holds that the fundamental space in which entities evolve is not three-dimensional, but instead 3N-dimensional, where N is the number of particles standardly thought to exist in three-dimensional space. I show that the state of three-dimensional objects does not supervene on the state of objects in 3N-dimensional space. I also show that the only way to guarantee the existence of the appropriate mental states in the wave function ontology has undesirable metaphysical baggage: either mind/body dualism is true, or circumstances which we take to be logically possible turn out to be logically impossible.While our theory can be extended formally in a logically consistent way by introducing the concept of a wave in a 3N-dimensional space, it is evident that this procedure is not really acceptable in a physical theory... (Bohm 1957, 117)     

MIND‐INDEPENDENCE AND THE LOGICAL SPACE OF WRIGHT'S REALIST‐RELEVANT AXES

This paper continues the work begun by Crispin Wright of identifying, articulating, and explaining the relations between various realist‐relevant axes that emerge when it is conceded that any predicate capable of satisfying a small range of platitudes is syntactically and semantically adequate to count as a truth predicate for a discourse. I argue that the fact that a given discourse satisfies the three realist‐relevant axes that remain if evidence‐transcendent truth and reference to evidence‐transcendent facts are ruled out by Dummettian meaning‐theoretic considerations is not sufficient for what I have elsewhere called “modest metaphysical realism.” I conclude that mind‐independence marks yet another realist‐relevant axis and explore the relationships between the proposed mind‐independence axis and the realist‐relevant axes identified by Wright.     

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.