“I am deeply moved if I see one man suffering and would risk my life for him. Then I talk impersonally about the possible pulverization of our big cities, with a hundred million dead. I am unable to multiply one man’s suffering by a hundred million.” ­—Albert Szent-Györgyi

The Senate Committee on Foreign Relations just concluded a historic hearing today on the executive’s authority to use nuclear weapons. This puts a spotlight on Pres. Donald Trump’s recent threat to “totally destroy North Korea” and calls attention to the fact that we have created weapons whose vast destructive power is beyond our easy comprehension. Due to a cognitive tendency called “psychic numbing,” Mr. Trump fails to acknowledge, let alone appreciate, the consequences of exterminating 25 million people.

Observing the survivors of the atomic bomb detonation in Hiroshima, psychiatrist Robert Jay Lifton found they shared a diminished capacity or inclination to feel. The survivors described to him how they had become “insensitive to human death” and “temporarily without feeling.” Dr. Lifton called this state psychic numbing and described it as “a useful defense mechanism” that “prevents the mind from being overwhelmed and perhaps destroyed by the dreadful and unmanageable images confronting it.” But psychic numbing isn’t exclusive to the A-bomb survivors, and it isn’t always helpful. Recent research shows it to be widespread and often destructive.

It is well recognized that two modes of thinking guide our behavior, fast and slow, and President Trump’s threat reflects the former. Fast thinking, relying on gut feelings honed by direct experience, was effective enough to enable our species to survive a long and dangerous journey from the cave to the modern world. Slow thinking is more recent in origin. Our brains evolved the capacity to think symbolically and apply logic and reason to guide our decision-making. Slow thinking enables us to imagine and critically evaluate consequences beyond those right in front of our eyes. But the human mind is lazy, and fast, intuitive thinking is easier to rely on as our default mode. When the potential consequences of our decisions are extreme and outside the realm of our direct experience we have to recognize the need to think more carefully and make the effort to do so.

Fast thinking enables us to feel strongly about and act vigorously to protect one identified person. But this sensitivity to the value of a life is limited. The feeling system is incapable of escalating in proportion to the death and misery of many victims. It can’t multiply, as Albert Szent-Györgyi insightfully observed. The single life that feels so important to protect loses its value against the backdrop of a larger tragedy. Quickly contemplating the suffering of countless unidentified people leaves us numb and indifferent and thus lacking an adequate understanding of their plight. No wonder we allow genocides and other mass atrocities to occur again and again, in addition to other human and environmental crises such as mass incarcerations, chronic but curable diseases, and extinction of endangered species.

This makes President Trump’s declaration at the UN General Assembly that, if threatened, the U.S. would totally destroy North Korea, abhorrent. The idea of 25 million individuals dying on the other side of the world is an abstraction that neither he nor any of us can comprehend without reflection. But a head of state overtly threatening the total destruction of another society is not abstract; it is a careless, impulsive utterance, unchecked by the rational faculties of slow thinking.

An intuitive thinker and communicator, the president likely knows that people are moved by the suffering of individuals. He criticizes North Korea for crimes against “an innocent American college student” and “a sweet 13-year-old Japanese girl,” sympathetic victims and, important for persuasion, single identified individuals. But the president seems blind to his own bias toward caring more about the lives of the few than about the lives of millions. In his UN address in September, he also bemoaned the Syrian dictator Bashar al-Assad’s use of chemical weapons on “innocent children.” He claimed to be greatly moved by the suffering of innocent Syrians in the April 2017 sarin gas attack, particularly when shown two images: young, listless children being splashed with water in a frantic attempt to cleanse them of the nerve agent; and an anguished father holding his dead twin babies, swathed in soft white fabric. But now he threatens to annihilate millions of North Koreans.

A way to counteract numbing when contemplating the deaths of large numbers of people might be to remember that each individual has a life, a story, and a family. As the Holocaust survivor Abel Herzberg said, “there were not six million Jews murdered; there was one murder, six million times.” By humanizing the numbers and imagining some of the individuals they represent, we may less easily succumb to the numbing that normally accompanies large losses of life, and we might understand President Trump’s threat as not one to destroy a country but rather to kill a North Korean child, mother, or father 25 million times. An even better way to counteract psychic numbing would be to employ analytic and deliberative procedures that lend meaning to the dreadful reality beneath the surface of the numbers and force careful weighing of the pros and cons for a menu of possible actions, i.e., slow thinking.

Former Secretary of State George Schultz recently commented on the president’s authority to use nuclear weapons: “The important moment is when you put your hand on the nuclear trigger. You’re not president then, you’re God. Where is it written that a man should be able to press a button and kill a million people?” To prevent fast-thinking from resulting in catastrophe Congress should bar the president from impulsively launching a nuclear first strike on his own, for example, by requiring that any order to issue a nuclear strike must go through multiple decision-makers such as the secretaries of Defense and of State.

Fortunately, nuclear bombs have not been unleashed on civilian populations since 1945. But it is naïve to believe that this restraint will continue indefinitely as these weapons proliferate and diplomatic negotiations between hostile nations are undercut by social media messages, fast-moving, unvetted, and possibly intended to deceive or to trigger anger and aggression.

We must employ the best quality of our slow thinking to create policies and procedures that ensure nuclear weapons will never be used again.