Then there was another young man who was with me, namely Freeman Dyson. He was an Englishman who had studied mathematics in the Tripos at Cambridge. And, GI Taylor, who was a professor at Cambridge, not in physics but in hydrodynamics. GI Taylor, whom we... I knew very well from Los Alamos, who had consulted for us, wrote me a letter. 'Well, I have here a graduate student,' in typical English understatement, 'who is not entirely stupid. It would be nice if you would take him on as a graduate student.' So I wrote back that I would be glad to take him on. And it turned out that Dyson knew everything. I gave him a problem, namely to do the Lamb shift now, not for an electron which has spin a half, but for a particle of spin zero. And I thought this would be a thesis problem. Well, he came back in... in about two weeks, asking some questions which I couldn't answer, but he found the answers himself, and in two more weeks, he came back with the answer. The Lamb shift was very similar for a particle of spin zero, and I told him 'Well, OK, now you write this up and publish it.' He was astonished that this was enough to be published. But it was, I think maybe it came just about the same time as... as the publications by the... by Schwinger and Feynman, maybe it was a little earlier.

So Dyson was very much interested in Feynman's work, and talked to Feynman constantly, following Feynman's developments. And he... knew about Schwinger's work, he went to... to Ann Arbor to listen to Schwinger at the summer conference. And then Dyson was able to show that Schwinger's approach and Feynman's approach were really equivalent, which was not at all obvious because they seemed totally different. Dyson, after spending a year here, went to the Institute of Advanced Studies, on my suggestion, and Oppenheimer gave him a hard time. Oppenheimer had really not understood Feynman's work. And it took a long time before Oppenheimer recognized that Dyson was a really excellent physicist. In fact, it took an invited lecture by myself to present Feynman's theories to Oppenheimer's seminar, I think only after that, Oppenheimer came around to Dyson and said 'Well, maybe you are right, and maybe this is a good theory.'