You often hear "most of everything is made up of empty space", referring to the idea that atoms only have mass in their nucleus. It seems to me that this is trying to explain physics in terms of everyday intuition, rather than the other way around. Specifically we have this intuitive notion of "solid stuff" and upon learning about the structure of the atom it chafes against that notion. But really, there never was "solid stuff" to begin with, it was only ever electromagnetic force keeping objects in rigid equilibrium, at the macroscopic scale. However, I can't be sure to extend this down to the fundamental particles as well. Perhaps protons have "actual volume". I hope this isn't too much of a philosophical question (or an argument about definitions) but I am hoping there is an actual concrete answer.