Feynman was asked in a seminar why the individual terms of the pertubation expansion have meaning. Basically he cannot fathom the question and his (correct) ans

Feynman was asked in a seminar why the individual terms of the pertubation expansion have meaning. Basically he cannot fathom the question and his (correct) answer is only the whole sum has a meaning. From 10:00 onwards, quite interesting, https://www.youtube.com/watch?v=72us6pnbEvE&list=PLYuIDo1vZpg3Mwm48ecZJR_i99ThPyo7V&index=1 https://www.youtube.com/watch?v=72us6pnbEvE&list=PLYuIDo1vZp... Of course virtual particles are only present in the individual terms of the pertubation expansion, so their reality is as iffy.