Why do men commit evil? Were the kommandants who ran the Nazi death camps psychopaths? Did they have subnormal intelligence? Were they just ordinary men who made appalling decisions?

I have been thinking about these questions ever since I found out that my great-uncle, Hanns Alexander, a German Jew, was a Nazi Hunter. At the end of the Second World War he tracked down and caught one of the worst mass murderers of all time, Rudolf Höss, the Kommandant of Auschwitz.

These were also the questions that a team of American psychologists and psychiatrists were directed to answer during the Nuremberg Trials that opened on November 20, 1945, six months after the war’s end.

Charges of crimes against humanity were read out against 24 of the highest-ranking Nazis then in captivity, including Ernst Kaltenbrunner, chief of the Reich Security Main Office and the highest-ranking SS officer after Himmler’s death.

With so many senior Nazis held in one place at the same time, the Americans instructed a panel of psychologists to conduct exten­sive interviews and tests with the defendants. Such horrific crimes were committed surely by damaged men, men different in some fundamental way from the rest of humanity.

Among the defendants examined was Rudolf Höss, the Kommandant of Auschwitz. Unlike the others held in Nuremberg, Höss had been intimately involved in the design and day-to-day operations of the extermination camps.

First he was visited by Gustave Gilbert, a New Yorker born to Jewish-Austrian immigrants. Gilbert later wrote about his meeting with the Kommandant in his 1947 book Nuremberg Diary.

Gilbert asked for a brief career summary, and was surprised when Höss admitted in an unemotional tone that he had been responsible for the deaths of more than two and a half million Jews.

The American asked how it was possible to kill so many people. “Technically,” answered Höss, “that wasn’t so hard—it would not have been hard to exterminate even greater numbers.” Gilbert then pressed him for an emotional response, but Höss continued in a similar tone: “At the time there were no consequences to consider. It didn’t occur to me that I would be held responsible. You see, in Germany it was understood that if something went wrong, then the man who gave the orders was responsible.” Gilbert started to ask, “But what about the human—” before Höss interrupted, “That just didn’t enter into it.” After a few more questions, Höss said, “I suppose you want to know in this way if my thought and habits are normal.” “Well, what do you think?” Gilbert asked. “I am entirely normal,” said Höss. “Even while I was doing the extermination work, I led a normal family life.”

Relying on the often-discredited Rorschach ink-blot test, Gilbert concluded that “one gets the general impres­sion of a man who is intellectually normal but with a schizoid apathy, insensitivity, and lack of empathy that could hardly be more extreme in a frank psychotic.”

Two days later, a U.S. Army psychiatrist, Major Leon Goldensohn, came to visit Rudolf Höss. Thirty-five years old, Goldensohn was, like Gilbert, a Jew who had been born and raised in New York. Goldensohn had arrived recently in Nuremberg to replace Douglas Kelley, another American psychiatrist who had conducted interviews with many of the prisoners (and would later publish his findings in a 1947 book Twenty-two Cells in Nuremberg.)

Goldensohn made detailed notes of his encounter with the kommandant, which were posthumously published in 2005 in the volume The Nuremberg Interviews.

When he arrived in the cell, sucking at a pipe dangling from his mouth, Goldensohn found the prisoner sitting on the edge of his cot with his trousers rolled up, bathing his feet in a tub of warm water.

Through an interpreter, Goldensohn asked him how he felt mentally. Rudolf Höss replied: “I feel less nervous now than I did.” He was then asked if he felt upset over what he had done in Auschwitz. “I thought I was doing the right thing,” said Höss. “I was obeying orders, and now, of course, I see that it was unnecessary and wrong. But I don’t know what you mean by being upset about these things because I didn’t personally murder anybody. I was just the director of the extermination program at Auschwitz. It was Hitler who ordered it through Himmler and it was Eichmann who gave me the orders regarding transports.”

When Goldensohn asked if he was haunted by nightmares—by images of the executions, gas chambers, or burning corpses—Höss replied: “No, I have no such fantasies.”

In a letter, written on 20 May 1946, Goldensohn gave his assess­ment: “His character is that of the amoral psychopath, which in itself, and correlated with his personal development history, indicates a dearth of parental love and unconscious hostility toward the father.”

On 15 April 1946, Rudolf Höss provided his testimony at Nuremberg. In its candor and detail regarding the mechanics of the Final Solution it changed the course of the trial.

Rudolf Höss’ testimony was reported around the world. The New York Times described it as the “crushing climax to the case.” In Britain, The Times of London went further. They said of Höss’ signed testimony: “its dreadful implications must surpass any document ever penned.”

A few days later, Rudolf Höss was handed to the Polish authorities to face his own trial. In April 1947, the former kommandant was hung on the gallows next to the old crematorium in the Auschwitz concentration camp.

The conclusion of the psychologists and psychiatrists at Nuremberg was clear: they both decided that though Rudolf Höss was intelligent, he was mentally ill: a psychopath, psychotic, amoral, lacking empathy.

But Rudolf flatly denied this to be the case. He declared himself to be normal. He regretted, at most, doing something unnecessary. Overseeing the murder of over a million people had left him unhaunted by “fantasies.”

The impression of the mental health professionals was also contradicted by two of the intelligence officers who interrogated Rudolf Höss.

First, there was the British war crimes investigator, Captain Hanns Alexander, my great-uncle Hanns, the German Jew turned British soldier, who had arrested the kommandant. Alexander had expected Höss to be a monster and was surprised to find him to appear “normal.”

Then there was Whitney Harris, the American prosecutor (and member of the OSS) who took Höss’s affidavit in Nuremberg. Harris said that Höss appeared like a “grocery clerk,” someone you would pay no attention to if you met him on the street.

This view that Höss was “normal,” no different essentially from other human beings, is supported by the kommandant’s own daughter, Brigitte, who said in a recent interview that her father was “kind” to her as a child, indeed he was “the nicest father in the world.” Brigitte even recalled that he looked “sad when he came back from work.” Brigitte was also clear that, as far as an 11-year-old would be able to tell, her father was sane.

An alternative theory of what underlies the character of the men and women who executed the Final Solution is put forward by Hannah Arendt. She argued that these men and women were typically not psychopaths or two-dimensional monsters. Rather they were ordinary men, who made a series of terrible decisions with horrific consequences.

To paraphrase Hannah Arendt—as portrayed in the recently released movie of the same name—the Nazi war criminal’s actions stemmed from her well-known phrase “banality of evil,” not as a result of mental illness but as a result of a lack of thinking. Their greatest error was delegating the process of thinking and decision-making to their higher ups. In Rudolf Höss’s case, this would have been his superiors, particularly Heinrich Himmler.

To many this conclusion is troubling, for it suggests that if everyday, “normal,” sane men and women are capable of evil, then the atrocities perpetrated during the Holocaust and other genocides could be repeated today and into the future.

Yet, this is exactly the lesson we must learn from the war criminals at Nuremberg. We must be ever wary of those who do not take responsibility for their actions. And we ourselves must be extra vigilant, particularly in this day of accelerated technological power, heightened state surveillance, and global corporate reach, that we do not delegate our thinking to others.