Università di Firenze, November, 30, 2021, h. 12.30-13.30 CET

We discuss the way in which the question “What is a particle?” has been approached in the literature, between scientific and manifest views of nature. Historically, the notion of a particle has been at the center of various discussions in which technical, apparently more “scientific” descriptions were pitted against more qualitative ones, nearer to phenomena and sometimes also to everyday experience (see the debate about wave-particle duality, for example). Today, in scientific textbooks the notion of (elementary) particle is usually presented as primarily shaped by the physical-mathematical apparatus of the theory, like the (irreducible) representations of the fundamental symmetry groups in the case of quantum field theories. In the philosophical literature, this has motivated a structural approach to the question of physical objects, and, notoriously, also further philosophical commitments about the nature of physical reality itself (cf. ontic structural realism). Here, we address the issue by assuming that, given the complexity and perhaps ambiguity of the notion at stake, it is necessary to go beyond general statements in physics textbooks, and focus on the actual use of “particles” in scientific practice. From this perspective, it is helpful to employ a historical-critical approach, looking at the way in which the notion of a particle was transformed in contemporary physics in the interplay of theory and experiment.