“Modern physics does not treat matter as a fundamental material substance in the traditional philosophical sense.”

In quantum field theory particles lose the status of primary substances (albeit the particle jargon is still used to describe observed phenomena), being defined as excitations of quantum fields.

The Standard Model of particle physics is a quantum field theory. Therefore, its fundamental elements are quantum fields and the excitations of these fields are identified as particles.

According to the ‘Received View’, which was elaborated as the quantum revolution was taking place, quantum theory implies that the fundamental particles of physics cannot be regarded as individual objects in this sense. … The argument for the above conclusion – that the fundamental objects of physics cannot be regarded as individuals – can be summed up as follows: First of all, both ‘classical’ and ‘quantal’ objects of the same kind (e.g. electrons) can be regarded as indistinguishable in the sense of possessing the same intrinsic (that is, state-independent) properties, such as rest mass, charge, spin etc.

In contrast to our modern notion of matter as substance, which exists independently, Aristotle’s matter is a principle that does not exist on its own but rather always in partnership with a form (e.g., either of the two contraries at the limits of the change). … Matter in modern thought, especially the early period, was conceived as existing on its own—that is, substantially—with more complex entities such as organisms having a derivative existence, similar to that of a machine, with parts outside each other and only extrinsically related. In contrast to this mechanical philosophy, matter for Aristotle is not a substance and never exists on its own. … If we remove Descartes’ poorly founded assumption about the nature of matter, we can return to Aristotle’s more fully human conception of matter, as the substrate of change, where “change” is not arbitrarily restricted to locomotion. Matter in this conception, being definitionally linked to motion, is also inherently indefinite. This indefiniteness or potency was rediscovered as a property of matter in the 20th century with quantum mechanics

All this leads to consider the need to elaborate new ontologies that go beyond our present conception of matter, including space–time itself in this category, and thus overcoming the old debate between relationalism and substantivalism.

Aside from matter fields, it is also common to consider relativistic spacetimes with certain types of material point particles, the treatment of which further supports the interpretation of each p∈M as an atomic event or material coincidence. … We allow test matter into our ontology only because it is an approximation of matter with relatively meager energy and momentum; we allow particles into our ontology only because they are an approximation of matter that is relatively localized. … That our interest in test particles is thus only derivative suggests that Histories, Freedom, and Light should be derivative, too, from more fundamental principles about matter fields, namely their equations of motion and contributions to energy–momentum.

The phenomenology of the SM is clearly based on the notion of interacting particles, that is, discrete quanta of matter that undergo interactions, as well as creation and decay processes. … Gauge-independent, localised bundles of interaction charges are a long distance form the classical intuitive image of a matter point, while still avoiding exotic metaphysics such as relationships without relata, Platonic ideals, or highly abstract mathematical objects crowding every point of space-time.

Since QFTs are formulated in terms of fields (i.e., mathematical expressions that associate quantities with points of spacetime), the issue is whether the formalism can be interpreted in terms of a particle notion. What is at stake is whether QFT, one of our current best physical theories, supports the inclusion of particles in our ontology. This paper advances an argument that, because systems which interact cannot be given a particle interpretation, QFT does not describe particles.

QFT taken seriously in its metaphysical implications seems to give a picture of the world which is at variance with central classical conceptions of particles and fields, and even with some features of QM.

The most common view of the ontology of RQFT recently has been that it includes only fields: Relativistic quantum fields are considered fundamental, and their amplitudes are always well defined in the interacting case; particle-quanta, if accepted at all into the ontology of RQFTs, are considered entirely reducible to fields and well defined only in those limited situations in which the Hilbert-space operators counting them are well defined, that is, in interaction-free limits

Did Gell-Mann (or anyone else) at that time believe that quarks were really physical things? – No. People (including Gell-Mann) were thinking of quarks as a kind of theoretical device / construct for ‘systematizing’ i.e. explaining a lot of hadron spectroscopy data, as opposed to ‘items of physical reality’.

However, later developments in science, especially in the twentieth century, have brought about such profound changes that classical concepts of matter are no longer viable. These new developments profoundly alter the statements of philosophical doctrines and problems traditionally associated with matter.

The theories and discoveries of thousands of physicists since the 1930s have resulted in a remarkable insight into the fundamental structure of matter: everything in the universe is found to be made from a few basic building blocks called fundamental particles, governed by four fundamental forces.

The consensus view among philosophers of physics is that relativistic quantum field theory (QFT) 1 does not describe particles. That is, according to QFT, particles are not fundamental entities.

Based on this paradigm, the ontologist of QFT may be (and have been) tempted to interpret the objects of the world—elementary particles and quantum fields—as substances. However, over the past three decades, philosophers have worked to demonstrate that such a paradigm—sometimes dubbed ‘myth of substance’ (Seibt 2002)—might be untenable (or has to be modified) in light of quantum theory (Teller 1995). … In fact, the myth of substance designates the presumption that the Aristotelian substance‐attribute dualism is a necessary framework for ontology (Seibt 2002) so that it is even considered as a ‘law of thought’ (Kuhlmann et al. 2002). On this view, fundamental entities must be ultimate subjects of predication, fully deter minate bearers of properties and persisting individuals that can be re‐identified across time. Seibt argued that this package is not an a priori constraint on metaphysics but a contingent set of assumptions that generate internal tensions when confronted with modern physics, including QFT.

In the early modern period, this practice begins to change, with many philosophers offering new characterisations of substance, or rejecting the notion of substance entirely. … Descartes appears to be the first prominent thinker to say this explicitly. Descartes' influence, respecting this and other topics, was reinforced by Antoine Arnauld and Pierre Nicole's Port-Royal Logic, which, towards the end of the seventeenth century, took the place of Aristotle's Categories as the leading introduction to philosophy. … The concept of substance lost its central place in philosophy after the early modern period, partly as a result of the criticisms of the British empiricists. However, philosophers of the twentieth and early twenty-first centuries have shown a revival of interest in the idea, with several philosophers arguing that we need to accept the concept of substance to account for the difference between object-like and property-like things, or to account for which entities are fundamental, or to address a range of neighbouring metaphysical issues.

(Oderberg 2007, 2014, 2023, and Brower 2014 argue that prime matter is logically coherent and compatible with modern science; for an opposing view, see Koslicki 2018, ch. 2.)

Super-substantivalism (of the type we’ll consider) roughly comprises two core tenets: (1) the physical properties which we attribute to matter (e.g. charge or mass) can be attributed to spacetime directly, with no need for matter as an extraneous carrier “on top of” spacetime; (2) spacetime is more fundamental than (ontologically prior to) matter.

The notion that quantum field theory (QFT) can be understood as describing systems of point particles has been all but refuted by recent work in the philosophy of physics. … If the particle concept cannot be applied to QFT, it seems that the field concept must break down as well. … In the end I will suggest an alternative ontology for QFT in terms of an algebra of observables.

According to the alternative “field approach,” we replace wave functions over particle configurations with wave functionals over field configurations—viewing quantum field theory as a theory of fields in quantum superpositions of different classical states. The debate between these approaches is a debate as to whether fields or particles are more fundamental.

Another challenge is to account for the remaining referents of General Relativity, namely, gravitating objects. I suggest that physical objects can be understood as clusters of processes, and hence can emerge as inhomogeneities in the growing pattern of events. … In this view, energy emerges as well, just as a measure of the density of basic events. Objects, physical things, would be nothing else than clusters of events.

In the classical view, space and time are the containers; matter is what is contained. The distinctive property of matter is that it carries energy and momentum, quantities that are conserved over time. … When these conversions proceed, the matter contained by space and time, as captured by its energy and momentum, loses its unequivocal character as content of space and time. It becomes entangled with its container in the structure of space and time itself.

First, classical field theory elevated fields to coequal status with particles, and subsequently quantum field theory (QFT) (arguably) demoted particles to a second class if not epiphenomenal status. This ascendancy of fields seems at first to be a god-send for the substantivalist since it seems to lend itself to the view that spacetime is the only basic substance qua object of predication. But diffeomorphism invariance as a gauge symmetry seems to wipe away spacetime points as objects of predication. Coming to grips with the ramifications of SGC indicates that we need to rethink the traditional subject–predicate ontology/ideology.

Another challenge is to account for the remaining referents of General Relativity, namely, gravitating objects. I suggest that physical objects can be understood as clusters of processes, and hence can emerge as inhomogeneities in the growing pattern of events. … Objects, physical things, would be nothing else than clusters of events. The ontology of Quantum Gravity, and of the world, under this perspective, would be a maelstrom of basic events; the things, people, galaxies of the universe, arise as a patterned poset in that storm.

The model is a quantum theory of fields that is based on “gauge” symmetry.

Rynasiewicz (1996) presents Einstein’s argument as evidence of the difficulty, if not irrelevance, of applying the traditional “substantival versus relational” dichotomy to modern physics

Technically, quantum field theory provides the mathematical framework for the Standard Model, in which a Lagrangian controls the dynamics and kinematics of the theory. … Each kind of particle is described in terms of a dynamical field that pervades space-time.

The Standard Model of Particle Physics is scientists’ current best theory to describe the most basic building blocks of the universe. It explains how particles called quarks(which make up protons and neutrons) and leptons (which include electrons) make up all known matter.

We shall see that the second viewpoint above is the most useful: the field is primary and particles are derived concepts, appearing only after quantization.

Quantum physics and special relativity however, complicate the picture through the identification of matter and energy, particle and wave.

By the early twentieth century, studies on radioactivity had shown that matter can decay; it turned out that the atoms of physics are not immutable and that they are in fact divisible into smaller particles. Moreover, these smaller particles were electrically charged, and it seemed that no understanding of matter would be possible without taking into account its electrodynamic properties. The philosophical ideal of primitive, essentially property-less bits of matter was now fully abandoned.

It covers the theoretical background of the Standard Model of particle physics in a didactically reduced way and primarily serves as a source of information for teachers, although the texts should be understandable for advanced or highly interested students as well. The three base concepts of the Standard Model, namely charges, interactions and particles as well as their dependencies are introduced.

Philosophical reflection on quantum field theory has tended to focus on how it revises our conception of what a particle is.

The understanding of matter in modern physics throws up challenges for philosophy and theology that are not well met by the traditional categories of Platonic and Aristotelian thought.

The Standard Model consists of 17 fundamental particles. Only two of these – the electron and the photon – would have been familiar to anyone 100 years ago. They are split into two groups: the fermions and the bosons. … The fermions are the building blocks of matter. There are 12 fermions, split into six quarks and six leptons.

Forces arise due to the exchange of unobservable virtual particles.

The Standard Model of elementary particles lists 17 fundamental particles divided into two basic particle families: 1. Fermions (matter particles) 2. Bosons (force carrier particles)

We show that the Bohmian approach in terms of persisting particles that move on continuous trajectories following a deterministic law can be literally applied to quantum field theory.

This Element offers an introduction to selected philosophical issues that arise in contemporary particle physics, aimed at philosophers who have limited prior exposure to quantum field theory.

to events instead of substances, and to relations instead of intrinsic properties.

Physicalism is the claim that that there is nothing in the world but the physical.

Until the discovery of subatomic particles and the quantum mechanics governing them, many of Leibniz's speculative ideas about aspects of nature not reducible to statics and dynamics made little sense.

This paper provides an overview of the ontological frameworks proposed for Quantum Field Theory (QFT). It begins by examining the conceptual challenges inherent in developing an ontology for QFT and outlines three potential ontological strategies. Subsequently, it surveys the principal ontological approaches discussed in the literature.