Heisenberg–who of course had been a very, very great physicist a long time ago after the war, after his working on the Nazi uranium project–was not so good as a physicist any more. Heisenberg came up with a kooky idea that… about which he made a tremendous fuss. He wrote down the equation: Gamma.psi = psi psi psi and said that this equation–which didn't have much meaning actually since it was so singular-this equation somehow contained the key to elementary particle physics. He had to cope with the fact that theory was very singular and he postulated that somehow in the presence of a lot of interactions maybe the propagators went way down. And Harry investigated the spectral representation in order to see whether this would be possible or not. But by that time Heisenberg had had another screwy idea of a negative metric and how he could have a negative metric without having negative probabilities. I never figured that out. He also had some other screwy ideas. He didn't believe in strangeness. He thought there were only two fundamental objects: something like the neutron and proton, or perhaps they were the neutron and proton; and that the strange particles weren't really there. He got them by doubling the vacuum, so that the neutron had another state, the lambda particle. Presumably if he had two neutrons he would have to quadruple the vacuum in order to get nn, n lambda, lambda n, and lambda lambda. The whole thing made essentially no sense. At first Wolfgang Pauli somehow was prevailed upon to sign up with him and to investigate this theory in collaboration with him. Pauli then came to the US and spoke in New York where he was rather severely criticized, and then he came on to Pasadena where Feynman and I both worked on him. Feynman said, ‘Your theory is as indefinite as your metric’, and I gave him some more specific criticisms as to why I thought the theory didn't make any sense whatever. And from Pasadena, I believe, he wrote the letter renouncing his collaboration with Heisenberg, and after that he attacked this foolishness.
