The scientific realist wants to read the metaphysical picture of reality through our best fundamental physical theories. The traditional way of doing so is in terms of objects, properties, and laws of nature. For instance, there are families of fundamental particles individuated by their properties of mass and charge, which determine how they move. One could call this view an object-oriented metaphysics grounded on properties. In this paper, I wish to present an alternative view that one can dub a thin object-oriented metaphysics grounded on structure: there are fundamental entities with no fundamental properties other than the one(s) needed to specify their nature. I argue that my view has several advantages over the received one. In particular, I compare my proposal to the traditional view in the quantum domain and I argue that my view provides a better fit for both approaches to quantum metaphysics, namely the primitive ontology program and wave-function realism.
The scientific realist wants to read the metaphysical picture of reality through our best fundamental physical theories. The traditional way of doing so is in terms of objects, properties, and laws of nature. For instance, there are families of fundamental particles individuated by their properties of mass and charge, which determine how they move. One could call this view an object-oriented metaphysics grounded on properties. In this paper, I wish to present an alternative view that one can dub a thin object-oriented metaphysics grounded on structure: there are fundamental entities with no fundamental properties other than the one(s) needed to specify their nature. I argue that my view has several advantages over the received one. In particular, I compare my proposal to the traditional view in the quantum domain and I argue that my view provides a better fit for both approaches to quantum metaphysics, namely the primitive ontology program and wave-function realism.
In my dissertation I analyze the structure of fundamental physical theories. I start with an analysis of what an adequate primitive ontology is, discussing the measurement problem in quantum mechanics and theirs solutions. It is commonly said that these theories have little in common. I argue instead that the moral of the measurement problem is that the wave function cannot represent physical objects and a common structure between these solutions can be recognized: each of them is about a clear three-dimensional primitive ontology that evolves according to a law determined by the wave function. The primitive ontology is what matter is made of while the wave function tells the matter how to move. One might think that what is important in the notion of primitive ontology is their three-dimensionality. If so, in a theory like classical electrodynamics electromagnetic fields would be part of the primitive ontology. I argue that, reflecting on what the purpose of a fundamental physical theory is, namely to explain the behavior of objects in three--dimensional space, one can recognize that a fundamental physical theory has a particular architecture. If so, electromagnetic fields play a different role in the theory than the particles and therefore should be considered, like the wave function, as part of the law.Therefore, we can characterize the general structure of a fundamental physical theory as a mathematical structure grounded on a primitive ontology. I explore this idea to better understand theories like classical mechanics and relativity, emphasizing that primitive ontology is crucial in the process of building new theories, being fundamental in identifying the symmetries. Finally, I analyze what it means to explain the word around us in terms of the notion of primitive ontology in the case of regularities of statistical character. Here is where the notion of typicality comes into play: we have explained a phenomenon if the typical histories of the primitive ontology give rise to the statistical regularities we observe.
Scientific realism is the view that our best scientific theories can be regarded as (approximately) true. This is connected with the view that science, physics in particular, and metaphysics could (and should) inform one another: on the one hand, science tells us what the world is like, and on the other hand, metaphysical principles allow us to select between the various possible theories which are underdetermined by the data. Nonetheless, quantum mechanics has always been regarded as, at best, puzzling, if not contradictory. As such, it has been considered for a long time at odds with scientific realism, and thus a naturalized quantum metaphysics was deemed impossible. Luckily, now we have many quantum theories compatible with a realist interpretation. However, scientific realists assumed that the wave-function, regarded as the principal ingredient of quantum theories, had to represent a physical entity, and because of this they struggled with quantum superpositions. In this paper I discuss a particular approach which makes quantum mechanics compatible with scientific realism without doing that. In this approach, the wave-function does not represent matter which is instead represented by some spatio-temporal entity dubbed the primitive ontology: point-particles, continuous matter fields, space-time events. I argue how within this framework one develops a distinctive theory-construction schema, which allows to perform a more informed theory evaluation by analyzing the various ingredients of the approach and their inter-relations.
When metaphysicians pay attention to theories in fundamental physics, they are usually interested in their implications for fundamental metaphysics: they want to know what the theories imply or suggest concerning the ultimate structure of reality. This essay, by contrast, is concerned with the “derivative metaphysics” of quantum mechanics. I will be considering a certain hypothesis about the fundamental structure of reality, which I will call H. I am interested in H because it strikes me as embodying the most obvious, flat-footed way to read an account of the fundamental structure of reality off the mathematical apparatus of elementary quantum mechanics. But I won’t be defending this claim here, or trying to argue that the members of H are more plausible than other accounts of the fundamental structure of reality inspired by quantum mechanics. Instead, my question is: if H were true, could there be (non-fundamentally speaking, of course) such ordinary objects as plants, planets and people? More specifically: could there be such ordinary objects as ourselves and the things we are familiar with, having more or less the ordinary properties we take them to have? And more generally: given that the fundamental structure of a possible world is such as to make H true, what is its correct description in ordinary terms? Of course, I care about these questions in part because I want to explore the extent to which we might have good reason to believe H, or something akin to it. But even if H turned out to be consistent with our ordinary knowledge about the world of ordinary objects, it would obviously take a lot more work to show that it has any serious claim on our credence. At a minimum, one would have to say something about how likely we should regard our evidence as being, given H; one would want to make some sort of survey of alternative hypotheses; and one would want to take into account our specialised scientific knowledge as well as our ordinary knowledge, including the facts that make trouble for elementary quantum mechanics and force us to look beyond it to quantum field theory and ultimately towards some kind of theory of quantum gravity.
What is quantum mechanics about? The most natural way to interpret quantum mechanics realistically as a theory about the world might seem to be what is called wave function ontology: the view according to which the wave function mathematically represents in a complete way fundamentally all there is in the world. We argue that: • Strictly speaking, it is not possible to interpret quantum theories as theories about the wave function; • Even if the wave function is supplemented by additional non-ontological structures, there are reasons not to take the resulting theory seriously; • All quantum theories should be regarded as theories in which physical objects are constituted by a primitive ontology. The primitive ontology is mathematically represented in the theory by a mathematical entity in three-dimensional space, or space-time.
A realist, particle-based view of quantum theory—where the wavefunction no longer plays a central role—offers a clear, commonsense alternative to dominant metaphysical views. This book explores the metaphysics of quantum theory through a lens of scientific realism—the belief that successful scientific theories describe reality. It critically evaluates various interpretations, including structural realism, wave function realism, and the many-worlds view, highlighting their limitations. Valia Allori proposes a “spatiotemporal foundational ontology” approach, grounded in particles as fundamental entities evolving in three-dimensional space and time, following uniform, symmetric laws. This view is exemplified by Bohmian mechanics (pilot-wave theory), offering a constructive, commonsensical explanation of quantum phenomena. The wave function, in this framework, is not a physical object but plays a functional, law-like role in explaining interactions. Further, the book advances a radical thesis: fundamental particles lack intrinsic properties like mass or charge and are instead “bare” objects distinguished only by the laws governing them. This thesis allows a middle path between traditional object-based metaphysics and eliminative structuralism. Ultimately, the author argues that had physics developed more rationally, instead of following a historical path shaped by contingent choices, the pilot-wave theory might have been the dominant interpretation, minimizing the proliferation of speculative alternatives.
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.