e Ontology of Electromagnetism

Electromagnetism is usually understood as a theory describing how charged particles and eletromagnetic elds interact. In this paper I argue that a double ontology comprising both particles and elds is problematic. Either we should think of electromagnetism as a theory about charged particles directly interacting with each other, or as theory of elds whose local interactions are manifested as eld quanta, called “particles.” From a purely theoretical point of view the choice between a particle and a eld interpretation does notmattermuchwhen it concerns classical electromagnetism; both interpretations are possible and, as shown by Quine, there is a general method for translating a theory about one kind of objects into a theory assuming another kind of objects, provided these theories are empirically equivalent. From an empiricist point of view, however, the particle interpretation is the choice, since some particles are directly observable. Testable predictions of electromagnetism are predictions of the motion of charged bodies, in theory represented as particles, so this must be the empiricists’ choice of ontology. In quantum electrodynamics one is however forced to chose a eld ontology, since a particle ontology for this theory is impossible. So called “quantum particles” are eld quanta, which cannot be treated as individuals making up a domain of quantication. ere is thus a tension regarding ontology between classical and quantum electrodynamics. But this tension is nothing else than the much debated measurement problem of quantum mechanics.