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.

In early psychoanalytic thought, narcissism was - and still, of course, is - self-love. The early psychoanalysts used to talk of libido directed at the self. That now feels a little quaint, that kind of language. But it does include the most fierce and self-displaying form of one's individual self. And in this way, it can be dangerous. When you look at Donald Trump, you can really see someone who's destructive to any form of life enhancement in virtually every area. And if that's what Fromm means by malignant narcissism, then it definitely applies.

But I spent just two calendar years at Cornell University, though it was covering more than three years of work, and then went to medical school and did become interested in psychiatry, and even helped form a kind of psychiatry club in medical school.

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.

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.

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.

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.