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.

As a kid I was fascinated with sports, and I loved sports more than anything else. The first books I read were about sports, like books about Baseball Joe, as one baseball hero was called.

Trump has a mind that in many ways is always under duress, because he's always seeking to be accepted, loved. He sees himself as constantly victimized by others and by the society, from which he sees himself as fighting back. So there's always an intensity to his destructive behavior that could contribute to his false beliefs.

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.

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.

Again, I was influenced by my father, who was very much an atheist and took pride in combating the traditional or orthodox forms of Judaism, which his parents and which my mother's parents were very steeped in.

Every adult in the world has some sense that he or she might be obliterated at any time by these weapons that we have created.