Dear all, We are pleased to announce that on Thursday, May 21 at 5.00pm (CET), Giovanni Valente (Politecnico di Milano) will give the talk Approximations that matter: virtual particles as carriers of interactions as part of the Lugano Philosophy Colloquia Spring 2026 organised by the Institute of Philosophy (ISFI) at USI. This hybrid talk will take place in Room Multiuso FTL Building (USI west campus) and online via Zoom. If you are interested in joining online, please write to events.isfi(a)usi.ch. Here is the abstract of the talk: In this talk, based on joint work with Nicolò Cangiotti and Gianni Arioli, I will develop an indispensability argument in support of the existence of virtual particles in scattering processes. In order to avoid the Paradox of Infinite Limits, which allegedly poses a challenge to scientific realism, one needs to de-idealize the fictitious systems introduced by the two limiting procedures employed in the perturbation scheme, namely the infinite expansion in Dyson series and the limits for negative and positive infinite times associated with the assumption of free particles. I will show that these limits do not introduce essential idealizations, in agreement with scientific realism. What is more, according to our argument, unobservable virtual particles arise as essential approximations and they should be interpreted as propagators of the interaction responsible for subatomic scattering. As such, their existence is based on the use of approximations that matter. For more information: https://www.ftl.usi.ch/it/feeds/15142