Feynman reflected on how he could teach his original FLP’s volume 2 & 3 differently and better than in his first pass through the subjects five years earlier. The attendees wanted him to lecture a couple years on the subject matter in the original FLP and essentially let him give his revised, enhanced, and expanded lectures. This then led more naturally into QED with a good foundation layer established. Feynman also tailored his lectures more to the level of his audience understanding they were not freshman and sophomore undergraduates but post graduate, doctorate level scientists, employed doing advanced research.