you have infinities in classical physics aswell. What is the potential energy for a system of two electrons positioned at the same point in space?This makes me wonder just how fundamental and valid QFT as a framework really is, in general terms. I have only just begun studying QFT in recent weeks, so I'm still largely ignorant of the finer points and issues, but even in the most simplistic of textbook cases ( e.g. quantisation of Klein-Gordon fields ) there already seem to be fundamental issues and quite a bit of handwaving going on ("let's just subtract that infinity to fix that other infinity..."). I do not for a minute doubt or dispute the successes of the Standard Model in describing real-world physics, but the foundation this all stands on appears to me to be shaky and ad-hoc at best. Something just does not feel right about QFT to me; I can't put my finger on it, it's just a matter of intuition. I will keep learning, but there remains an itch that feels as if it badly needs to be scratched Am I the only one who feels that way ?