In a series of works published in the early 1960s, Herman Kahn, a RAND strategist, was arguing that the United States could survive an all-out nuclear war and even resume something like a normal life. Magazines like Life and Time were running features on civil defense that showed happy families emerging from their fallout shelters ready to build the world anew. Within a few days of a nuclear attack, a Time article predicted, people might begin to emerge: “With trousers tucked into sock tops and sleeves tied around wrists, with hats, mufflers, gloves and boots, the shelter dweller could venture forth to start ensuring his today and building for his tomorrow.”

No wonder Morgenthau thought Americans were in need of a healthy dose of nuclear terror. Like Kahn, he had become convinced that we must be willing to “think about the unthinkable.” But the optimism of Kahn and others seemed to make the unthinkable even more likely. Hopeful visions that we could survive or even prosper after a nuclear war gave cover to wage one. Morgenthau needed to find a way to make the unthinkable less likely.

Have we lost the ability to think about the unthinkable?

President Trump’s decision on Tuesday to pull the United States from the Iran nuclear agreement — not to mention the careless and unpredictable war of words he has waged with Kim Jong-un of North Korea over the past year — and the anxiety it has caused in countries across the globe suggest that we should listen again to the alarm that Morgenthau sounded.

“Death in the Nuclear Age” begins by invoking that most basic human fear — of death. It is “the great scandal in the experience of man.” It negates everything that “man experiences as specifically human in his existence: the consciousness of himself and of his world, the remembrance of things past and the anticipation of things to come, a creativeness in thought and action which aspires to, and approximates, the eternal.”

Human societies, Morgenthau wrote, have tried to transcend death. For much of history, we denied the reality of death through faith in the immortality of the body or the soul. In a secular age, this strategy is no longer available.