« this is the second in this series of lectures on quantum electrodynamics. None of you were there last time, I guess... since I had warned that today it would be completely incomprehensible »

« I don't think I could live without teaching. For a simple reason, when I can't find anything, I need something to hold on to; I have to be able to say to myself, "At least I exist, I do something, I am not useless." It's purely psychological. During my time at Princeton in the 1940s, I had seen what happened to all these geniuses that had been assembled in the Institute for Advanced Study. They had been chosen for their extraordinary intellectual abilities and had been offered the opportunity to live among themselves, comfortably seated in the middle of the woods, without any obligation to teach, without any obligation of any kind. Really it is not an enviable fate: there is only one thing to do: think and discuss; Ideas don't always come right away; but since we are here to have ideas, I imagine that in this kind of situation we must feel a little guilty, depressed at least. We are beginning to doubt, to worry that ideas do not come. And then nothing happens and the ideas still don't come. Nothing happens because there is no real activity, no situation that challenges you. We are cut off from all physicists in laboratories; students are no longer there to ask you embarrassing questions. It's a void. »

« I prefer to talk to you today about an area that has been perfectly well analyzed. It is this part of physics that never ceases to provoke my wonder and which is called quantum electrodynamics. »