The aim of this work is to study the ontological thesis defended by Ontic Structural Realism, which, in general, states that the ontological commitments should be focused in the relations and not on objects. This would be a more coherent realist stance towards modern physical theories. In first place we will study the ontological conception defended by the Ontic Structural Realism, which, broadly speaking, postulates that the ontological focus should be placed on relations rather than on objects. This, in turn, would constitute a realistic interpretation of the current physical theories. Secondly, as a possible defense to the position stated by Ontic Structural Realism, the concept of non-supervenient relations will be studied and it will be argued that it is this type of relations that acquires a fundamental character in Quantum Mechanics, as, for example, in phenomena such as the so-called quantum entanglement.
The aim of this work is to study the ontological thesis defended by Ontic Structural Realism, which, in general, states that the ontological commitments should be focused in the relations and not on objects. This would be a more coherent realist stance towards modern physical theories. In first place we will study the ontological conception defended by the Ontic Structural Realism, which, broadly speaking, postulates that the ontological focus should be placed on relations rather than on objects. This, in turn, would constitute a realistic interpretation of the current physical theories. Secondly, as a possible defense to the position stated by Ontic Structural Realism, the concept of non-supervenient relations will be studied and it will be argued that it is this type of relations that acquires a fundamental character in Quantum Mechanics, as, for example, in phenomena such as the so-called quantum entanglement.
In correspondence with the modal interpretations of quantum mechanics, Lombardi and Castagnino (2008) and da Costa, Lombardi and Lastiri (2013) have proposed an ontology of bundles of possible intrinsic properties for quantum mechanics, focused mainly on the issues of quantum contextuality and indistinguishability. Corresponding to the interpretation known as "relational quantum mechanics" (Rovelli, 1996), two ontologies based on relations have been proposed. Laura Candiotto (2017) advocates for a radical metaphysics of relations, considered by the author as an instance of the so-called "ontic structural realism". Alternatively, Andrea Oldofredi (2021) proposes an ontology of bundles of relations, considered by the author as an instance of the so-called "moderate structural realism". Since the 1980s, the topic of quantum entanglement has led several authors (Teller, Healey, Howard, Esfeld) to defend that quantum mechanics involves a form of holism. It has been argued that the holism of quantum mechanics supports the metaphysical thesis known as "priority monism" (Schaffer, 2010a). In this article, an ontology of quantum mechanics is proposed in which the properties of quantum systems have both a modal and a relational character. As a result, a holistic ontology of quantum mechanics is obtained, which is an instance of priority monism and moderate structural realism.
In this chapter it is argued that the decisive argument against the reducibility of causal relations comes from quantum physics. Bell’s theorem proves that no dynamics based on the local, intrinsic properties of quantum objects can yield the empirical predictions of quantum mechanics. Nonetheless, it is argued that quantum entanglement by no means implies that we have to abandon an ontology of objects in favour of an ontology of structures. All extant proposals for a quantum ontology of matter in spacetime are committed to objects, whose dynamics are determined not by their local, intrinsic properties, but by an holistic property instantiated by all the objects together—a structure that takes all the objects in the universe as its relata. The view set out in this chapter combines ontic structural realism with an ontology of objects that can be conceived as substances.
As far as classical physics is concerned, it is possible to trace causal relations between physical objects (i.e. particles in this case) back to intrinsic properties of these objects (such as their mass and charge). On this view, causal relations turn out to be internal instead of external relations, supervening on intrinsic properties of the relata (as proposed by Heil and Lowe). However, one can raise doubts about this view already in Newtonian mechanics. The decisive blow to this view comes from quantum physics, with Bell’s theorem proving that no dynamics based on local, intrinsic properties of quantum objects can yield the empirical predictions of quantum mechanics. Nonetheless, quantum entanglement by no means implies that we have to abandon an ontology of objects (i.e. substances such as particles) in favour of an ontology of structures (as claimed by French and Ladyman). Any of the known proposals for a quantum ontology of matter in space-time is committed to objects. However, on any of these proposals, what determines the dynamics of these objects are not local, intrinsic properties, but a global or holistic property instantiated by all the objects together – that is, a structure that takes all the objects in the universe as its relata. The view set out in this paper thus amounts to combining ontic structural realism with an ontology of objects that can be conceived as substances. This suggestion is illustrated by drawing on the ontology of quantum physics worked out by Bohm and Bell. 1.
The ontic structural realist stance is motivated by a desire to do philosophical justice to the success of science, whilst withstanding the metaphysical undermining generated by the various species of ontological underdetermination. We are, however, as yet in want of general principles to provide a scaffold for the explicit construction of structural ontologies. Here we will attempt to bridge this gap by utilizing the formal procedure of quantization as a guide to ontic structure of modern physical theory. The example of non-relativistic particle mechanics will be considered and, for that case, it will be shown that a viable candidate for an ontic structural realism framework can be constituted in terms of the combination of a state-space with Poisson bracket structure, and a set of observables, with Lie algebra structure. 1 Introduction2 Formulation Underdetermination and Structural Ontologies3 Quantization and Structural Ontologies4 The Case of Non-relativistic Particle Mechanics 4.1 Formulation underdetermination 4.2 The classical ontology 4.3 Quantum theory and the generalized structural ontology 4.4 Interpretation of results5 Conclusion and Prospects
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.
Standard quantum mechanics poses serious challenges to some principles deeply entrenched in traditional metaphysics. In particular, the theory defies the ontological category of individual object through three of its features: contextuality, non-separability, and indistinguishability. The difficulties have prompted the development of non-traditional ontological frameworks intended to account for the quantum domain. Some approaches advocate replacing the classical conception of a realm of objects endowed with properties by an ontology that either dispenses with the category of object altogether or treats it as a derivative notion. The Modal-Hamiltonian Interpretation (MHI) of quantum mechanics and Ontic Structural Realism (OSR) exemplify this position. MHI proposes an ontology in which quantum systems are non-objectual bundles of properties linked by definite physical relations. The OSR defends the ontological primacy of structures, within which objects are construed as nodes of relations. The aim of this article is to compare these two ontological approaches, highlighting both their points of convergence and their divergences, particularly in light of the ontological challenges posed by quantum mechanics. With this aim, the article is structured as follows. Section 2 outlines the ontology of MHI, introducing the distinction between type-properties and case-properties, characterizing quantum systems as non-objectual bundles, and analyzing the role of symmetry groups in providing physical content to the theory and governing actualization. Section 3 turns to OSR, examining its motivations, its distinction between physical and mathematical structures, and the modal character of structures. Section 4 offers a systematic comparison of the two approaches, considering their respective motivations and scope, their shared commitment to an object-free ontology, the role played by symmetry groups within each framework, and their contrasting interpretations of modality. Finally, Section 5 presents some concluding remarks.