The decisive point. Landau, a real communist, had been arrested by Stalin as a western spy. I heard some rumors before that. I did not hear a simple fact as impressive as that and as close to me as that and I can tell you, my final decision came even later and I'm now deviating from telling you things in proper se- time sequence. In the early '40s, I think actually in '43, after coming to Los Alamos, I read a book by a very wonderful Hungarian author, in English. The name: Arthur Koestler. The title: "Darkness at Noon". I don't remember another occasion where one book influenced me so thoroughly. I now know that Koestler had been a convinced communist, had worked for them for years and then turned against them and wrote this book. "Darkness at Noon". Noon. The triumph of communism in Russia, but darkness. The book is about a man like Landau, not Landau, arrested by Stalin's apparatus. And the book is really wonderful, because you could read three-quarters of it and you see the problem, you see the accusations, you hear the defense and if you pay attention to nothing but the book, you have no conclusion. You don't know who is right and you don't know who is wrong. And then you read the last quarter and it becomes clear, without any doubt, that Stalin and communism in the Soviet Union is the worst kind of dictatorship. Precisely because the book emphasizes doubts, causes the reader - if he's at all inclined to do so - causes the reader to think and gives the answers only at the end. In a way, that is an approach, not so very different from the approach in physics where the new science of quantum mechanics did arise, not as a simple, straightforward proof, but connected with a lot of doubts and giving the answer to that doubt. I read that book in the first month, the first few weeks I spent in Los Alamos in the early '40s - early month of '43. By the time I started to work very seriously on the atomic bomb, I was an anticommunist. But that followed a period of well over a decade where I was looking and searching for an answer.