With no classes to teach, with no obligations whatsoever. These poor bastards could now sit and think clearly all by themselves, OK? So they don't get an idea for a while: They have every opportunity to do something, and they're not getting any ideas. I believe that in a situation like this a kind of guilt or depression worms inside of you, and you begin to worry about not getting any ideas. And nothing happens, still no ideas come.
— Richard P. Feynman on lack of teaching at the Institute for Advanced Study, "Surely You're Joking, Mr. Feynman!"