In this essay,I argue that the basic entities in the causality organized hierarchy of entities that quantum field theory describes are not particles but fields.Then I move on to discuss,from the perspective of a structural realist,in what sense and to what degree this theoretical construction of fields can be taken as an objective representation of physical reality.
In this essay,I argue that the basic entities in the causality organized hierarchy of entities that quantum field theory describes are not particles but fields.Then I move on to discuss,from the perspective of a structural realist,in what sense and to what degree this theoretical construction of fields can be taken as an objective representation of physical reality.
One of the foundational challenges in both Quantum Field Theory and the philosophy of physics lies in the traditional binary classification of entities as either real or unreal. The classical view posits that material entities are real, while mental constructs or theoretical entities are unreal. However, quantum phenomena such as virtual particles challenge this simplistic dichotomy. These unobservable entities, by influencing measurable phenomena, raise profound questions about the nature and modes of existence. To address this, we propose a four-level ontological hierarchy that spans from the quantum vacuum and the virtual level to the quantum level and phenomenal reality, providing a coherent continuum from potentiality to actualization. This framework not only clarifies the interpretation of quantum theory but also offers a unified perspective linking the unobservable with the observable. In QFT, virtual particles play a crucial role in mediating forces and in correcting the measurable properties of real particles. They arise within the mathematical structure of Feynman diagrams and, despite being unobservable, produce real, measurable effects such as the Lamb shift and the Casimir effect. Philosophically, this raises deep ontological questions: if unobservable entities affect measurable phenomena, can they truly be dismissed as unreal? Conversely, if they are real, what mode of existence do they possess? The traditional dichotomy of real versus unreal is thus insufficient for interpreting the ontological implications of quantum processes. To overcome these limitations, we propose a four-level ontological hierarchy.
In this dissertation, I will argue that quantum field theory can be interpreted as a description of causal interactions. I will first discuss previous theories of physical causation, and come to the conclusion that they are inapplicable in quantum field theory. As a consequence, I will start to develop a new theory of causation by first analysing the concept ‘causation’ into the most basic and widely shared intuitions, in order to find out later whether these intuitions can be reduced to physics. I will then have a closer look on the intuition that causation is a directed relation, which is commonly regarded as incompatible with the symmetries of physics. I will present a new argument to the effect that causation and quantum field theory are compatible with respect to the directionality of causation. After that, I will analyse the theoretical description of interactions in quantum field theory, and in particular group structure, locality and local conservation laws will crystallise as the central concepts that a causal interpretation might be based on. Subsequently, I will discuss and present replies to what I believe are the most relevant objections to a causal interpretation of physics, namely, Haag’s theorem, the measurement problem and entanglement. In the final chapter of this dissertation, I will conjoin the results of the previous chapters to a new theory of causation for quantum field theory. The main result will be that a causal process is a quantum field theoretical interaction, i.e., the exchange of energy from an initial to a final state via a force.
Quantum field theory (QFT) can be analyzed in terms of its mathematical structure, its conceptual system for physical descriptions, or its basic ontology. The analysis can be done logically or historically. In this chapter, only the genesis of the conceptual foundations of QFT relevant to its basic ontology will be treated; no discussion of its mathematical structures or its epistemological underpinnings will be given. Some conceptual problems, such as those related to probability and measurement, will be discussed, but only because of their relevance to the basic ontology of QFT, rather than their intrinsic philosophical interest. Here, by basic ontology I mean the irreducible entities that QFT is invented to describe. The often mentioned candidates for the basic ontology of QFT, in fact of the physical world, are the discrete particle and the continuous field. Another possible candidate (the spacetime point) has also been suggested recently (Redhead, 1983). Since the aim of this chapter is to analyze the historical process in which the conceptual foundations of QFT were laid down, rather than the logical structure of QFT which philosophers of the present day treat, no discussion of the last possibility will be given. The content of this chapter involves the formation and interpretation, in a roughly chronological order, of the concepts of the wave function, quantization, quantization of the field, the vacuum, interactions between fields, and renormalization. The first two topics will be discussed in relation to the quantization of the field, with their role being taken as the starting point of the conceptual development of QFT.
This is an opinionated survey of some interpretive puzzles in quantum field theory. The problem of inequivalent representations is sketched, including its connections with competing accounts of physical equivalence. The controversy between variant formulations of the theory, algebraic versus Lagrangian, is given a conciliatory resolution. Arguments against particles are addressed, demarcating clearly between different forms of particle interpretation. Field interpretations are then considered, including wavefunctional, spacetime state realist and Heisenberg operator realist interpretations. Ruetsche’s coalesced structure interpretation is presented and juxtaposed with an alternative, more traditional view of the theory’s laws and state space. Finally, the CPT theorem is discussed, together with its implications about the nature of spacetime.
In this work, we focus on a very specific case study: assuming that quantum theories deal with “particles” of some kind (point particles in orthodox non-relativistic quantum mechanics, field excitations in quantum field theories), what kind of entity can such particles be? One possible answer, the one we shall examine here, is that they are not the usual kind of object found in daily life: individuals. Rather, we follow a suggestion by Erwin Schrödinger, according to which quantum mechanics poses a revolutionary kind of entity: non-individuals. While physics, as a scientific field, is not concerned with whether entities posited by a specific physical theory are individuals or not, answering this question is part of the quest for a better understanding of physical reality. Here lies, in large measure, the relevance of ontology.
This manuscript revisits quantum entanglement from a quantum field–theoretic perspective,with the aim of clarifying its conceptual status rather than proposing a new theory. The central claim is that quantum entanglement need not be understood as a mysteriousnonlocal phenomenon.When quantum fields are taken as the primary physical entities, entanglement followsnaturally from the non-separable structure of global field excitations.What appears puzzling in particle-based descriptions is thus revealed to be an expectedfeature of field-based ontology combined with reduced descriptions. The paper emphasizes a structural reading of the wavefunction as a description of fieldexcitations, and interprets entanglement as a consequence of restricting access to aglobally defined state.Locality is preserved at the level of operators, and all empirical predictions of quantumfield theory remain unchanged. No new dynamics, interpretations, or empirical claims are introduced.Instead, the work makes explicit a conceptual perspective that is already implicit instandard quantum field theory but is rarely articulated in a unified and accessible form.Formal details supporting the argument are provided in an appendix, while the main textfocuses on conceptual clarity. This work is intended as a contribution to the foundations of quantum theory, clarifyingthe relationship between entanglement, locality, and field-theoretic structure.