While Donald Trump doesn't have any systematic ideology, he does have a narrative, and in that narrative, America was once a great country, it's been weakened by poor leadership, and only he can make it great again by taking over. And that's an image of himself as a strongman, a dictator. It isn't the clear ideology of being a fascist or some other clear-cut ideological figure. Rather, it's a narrative of himself as being unique and all-powerful. He believes it, though I'm sure he's got doubts about it.

It may sound terrible, but I often say that the military saved me from a conventional life in the United States and I've never really thanked them for it, because I haven't exactly been pro-military in my work.

And I thought about the psychic numbing involved in strategic projections of using hydrogen bombs or nuclear weapons of any kind. And I also thought about ways in which all of us undergo what could be called the numbing of everyday life.

For anyone with the traits - of feeling himself victimized, of seeking to be the strongman who resolves everything, yet sees truth only through his own self and negates all other truth outside of it - is bound to become more malignant when he has power. Power then breeds an intensification of all this because the power can never be absolute power - to some extent it's stymied - but the isolation while in power becomes even more dangerous. Think of it as a vicious circle. The power intensifies these tendencies and the tendencies become more dangerous because of the power.

One reason that I embarked on a study of Nazi doctors was that in this personal journey, I had the feeling increasingly that I did want to do a Holocaust study and that increasingly I wanted it to be of perpetrators, which I thought was more needed.

The American president has particular power. This makes Trump the most dangerous man in the world. He's equally dangerous because of his finger on the nuclear trigger and because of his mind ensconced in solipsistic reality. The two are a dreadful combination.

People with what we call mental illness can indeed serve well, and people who have no discernible mental illness - and that may be true of Trump - may not be able to serve, may be quite unfit. So it isn't always the question of a psychiatric diagnosis. It's really a question of what psychological and other traits render one unfit or dangerous.