A luminous discussion of the ethics and practicalities of nuclear deterrence with a man who is as much a philosopher as a physicist. ET: "I think that the appropriateness of your response is a moral question, and there are some stable values in morality, and that is why I would object, under all circumstances, to a first strike. I would also say that if we are attacked, I would much rather have a defense, and we can have a defense, but I also think that we must be prepared to retaliate... If it so happens that many millions have to be killed, after many millions of us have died, I would say that the continuation of freedom means to me more than practically any other consideration." ...WFB: "Number one, are you permitted to speak on this subject, and if not, can we infer from your silence that the United States Government has a technological ace up its sleeve?" ET: "Let me start with the second question while I remember it. I am trying to work on that ace ... but I cannot yet tell you whether it will be an ace or a deuce."