In 1954, the United States Atomic Energy Commission held security hearing proceedings to investigate J. Robert Oppenheimer, the head of the Los Alamos laboratory, where the atom bomb was developed as part of the Manhattan Project. Feynman joined the Manhattan Project while still a graduate student at Princeton, and worked with Oppenheimer, as well as with several of the people who gave statements during the hearing, including Enrico Fermi and Hans Bethe, who testified in support of Oppenheimer, and Edward Teller, who initially was opposed to the hearing, but who at the same time, had long-time grievances against Oppenheimer. Teller, when asked whether Oppenheimer should be granted a security clearance, said that it would be wiser not to do so. After the trial, Oppenheimer's clearance was revoked. Teller's testimony against him led to outrage in the scientific community, leading Teller to be ostracized.

Feynman's notations give us a fascinating insider's look at the hearing, with numerous sections marked as "Lies!", "Not true", and "I wonder."