There were two problems which Cécile and I took along for Feynman to deal with... were the scattering of light by an electric field, and the scattering of light by light; especially the scattering of light by light had been a sort of a notoriously difficult problem. It had been more or less done by Euler and Kochel before the war with old-fashioned methods. It was a formidable calculation and it wasn't at all clear that we could do it by the new methods of Feynman. And it was something we had to get straightened out before this whole theory was really complete. So we asked Feynman about this, and he said, 'Let's see about that.' And he sat down and he just worked through it; in about three quarters of an hour he'd done the whole thing and it was the most amazing performance. He just - with his lightning calculations, it all came out very beautifully. It turned out that the third order effect was zero and the fourth order effect was finite and everything worked exactly the way we wanted. So after then, it meant that the theory really was consistent. And we talked about other things there and Feynman had an amazing proof of the Maxwell equations from quantum mechanics which I published after his death. He didn't want to publish it, he said it was just a joke, but finally after he died I decided it was time to have it published. It was something so clever and cute and it is in fact a rather illuminating idea, although I mean Feynman was right that it didn't lead anywhere, but still I'm happy that I was able to publish it in the American Journal of Physics some time after he died. So he told us about that, and other things. He was just bubbling over. He was so happy to have somebody to talk to, and so Cécile and I had a great time. And we came back to Princeton just bubbling with enthusiasm for Feynman and his way of doing things.