One of the most outstanding characteristics of human beings is their adaptability. As we readily learn to take new conditions of life for granted, so we have learned to live with the bomb. For nearly forty years we have lived in the shadow of possible cataclysmic disaster brought about by human action; and we treat this unprecedented danger simply as a background, on which we focus only occasionally, to the common business of living. What else is possible, save persistent hysteria? But, as part of a mechanism for avoiding hysteria, we are in danger of rendering the topic unreal to ourselves even when we are explicitly considering it, by treating it as an abstract question. We use the concepts of first strike, retaliation, megadeaths, and so forth, which we apply in just the spirit of those discussing strategy for a board game, while averting our minds from what it is that we are actually talking about. Indeed, if our concern is purely strategic, this does no harm, since the question then involves something isomorphic to a problem in a conceivable board game.