Carl von Weizsacker was a German physicist who worked on nuclear research for the German side in World War II. He continued to work in the field for another decade, before becoming a professor of philosophy in Hamburg. The interview starts in 1938-1939 when he learned of the discovery of uranium fission. At that point he decided that either the institution of war must be eliminated or "mankind will be abolished." He describes German scientific activity in the field as the war got underway and the initiative of the War Ministry to pull together physicists with an eye to developing a bomb. For their part, he says, the scientists were fairly sure that the process would be too difficult to accomplish during the course of the war. He notes that it is unclear whether Hitler was actually told about the prospect of nuclear weapons. He recalls the Hiroshima explosion and the disbelief, shock and even despair with which it was greeted by his colleagues. He also describes warmly his youthful experiences of regularly gathering with other atomic scientists at the Bohr institute in Copenhagen, and relates Werner Heisenberg's version of his ill-fated conversation with Bohr about the conundrum presented by the possibility of nuclear weapons production. He believes Bohr mistakenly assumed that Heisenberg was asking for his help, which led to a breach between the two men. Asked about the most surprising development of the nuclear age, he responds that it is the fact that nuclear weapons have not been used since Hiroshima.