Field-particle dualism, as in the title of our symposium, is a dualism of concepts that arose in physics together with the advent of electromagnetism as a field theory. In my talk, I would like to comment on two accompanying conceptual aspects of this dualism which were manifest from early on: A) the problem of matter and B) the question about the origin of its mass. While the problem of matter refers to the profound question of the relationship between matter and the electromagnetic field - and if the first can actually reduced to the latter, the origin of mass was in this vein soon sought to be found in the electromagnetic field entirely. It thus seems instructive to attempt to trace these aspects historically and ask in how far they stand at the origin of well known properties of contemporary theories, such as the division between bosons and fermions in Quantum Field Theory and the Higgs mechanism. I will argue that in the first case, there is indeed a historical connection to be made, while the situation in the second case is much more difficult. Even though, ideas involving the electromagnetic mass can surprisingly still be found in the late 1940s, it does not seem possible to establish a direct connection to the development of the Higgs mechanism which began in the 1950s.

“Les hypothèses, c’est le fonds qui manque le moins” claimed Henri Poincaré in his address to the 1900 Paris International Congress of Physics. Most of the physicists he referred to in his critique of recent work on the relationship between the ether and matter were assembled in Paris.
The Congress organisers assembled around 800 physicists from ‘all countries’ in a conscious attempt to bring together the current ideas and hypotheses ‘by which we are now trying to explain the constitution of nature and the laws that govern it.’ The ensuing ‘Rapports’ deliberately provided a snapshot of the ideas dominating physics at the beginning of the 20th century.
A tension runs throughout the ‘Rapports’, between a drive to unification and the increasing complexity of observed phenomena and proliferation of hypotheses. The opposition between matter and field – variously conceived as ether or field - is one manifestation of this tension.
Using Poincaré’s critique as a starting point, this talk uses the ‘Rapports’ to investigate the Congress as a locus of interaction between the various hypotheses explaining matter as an electromagnetic phenomenon at the beginning of the 20th century and the different conceptual and mathematical approaches to modelling.

Around the start of the twentieth century, the electron was seen by many physicists as offering the possibility of unifying the whole of physics under the electromagnetic worldview. This idea did not came out of nowhere. While the experimental study of the electron is often cited as giving rise to such unifying attempts, I will highlight another influence here, namely Heinrich Hertz's 'Principles of Mechanics'. I will indicate how, particularly in the German context, Hertz's work was seen as a blueprint for the development of fundamental theories that could account for mechanical, gravitational and electromagnetic phenomena in terms of the electron and its fields. I will focus in particular on two such attempts, by Wilhelm Wien and Max Abraham.

In the second part of my talk, I will then discuss the response by Albert Einstein and Max Planck to the challenge that the electromagnetic worldview posed to the special theory of relativity. This challenge, which was embodied by the experimental results of Walter Kaufmann on the velocity-dependency of mass that favoured the electromagnetic worldview, could only addressed at the time by reconceptualizing certain of the electron's properties as hidden. In this way, I will suggest, the relativistic response was equally well Hertzian in nature, although rather implicitly.