ABSTRACTThis paper is about the problem of the moral responsibility resting on any person to form rational beliefs about, and moral attitudes towards, the deterrent threat of mutual assured destruction (MAD), which still lies behind the graduated nuclear response strategies now more fashionably discussed by military experts. The problem is to decide what kinds of reasons there are, and how to arrive in the light of them at determinate conclusions about deterrence and unilateral disarmament. Consequential arguments would be powerful, if only they were determinate; but not only do they not point conclusively to one strategy rather than another, there is not even sufficient reason for accepting one rather than another of the competing optimising criteria by which the strategies might be assessed. So the reasons of other kinds against forming a conditional intention to retaliate with a massive second strike could be conclusive, if retaliation itself could do no (consequential) good, and if, as is claimed, the conditional intention could not be simulated. To form such an intention is held to be contrary to core values of a humane, rationalist culture. To assent to a nuclear retaliatory strike would do violence to the moral nature of anyone participating in such a culture, and to form an intention to make (or condone) such a strike would be a corruption of such a nature. So too would condoning the fostering of such an intention in others, as a way of making the retaliatory intention credible. The author accordingly considers this argument against MAD, and for unilateral nuclear disarmament, sufficient, given the inadequacy of the consequential arguments, while acknowledging that this might involve great sacrifice. The paper concludes, however, by considering whether anyone can reject nuclear deterrence who also believes that resistance to Nazism in 1939 was justified, given the then prevailing belief that the war might be massively destructive. The author holds that there is no inconsistency in both supporting resistance to evil, even at risk of total destruction, and in refusing to form or condone a conditional intention to do equivalent but pointless evil in order to make a threat credible.