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.

We have a duty to warn on an individual basis if we are treating someone who may be dangerous to herself or to others - a duty to warn people who are in danger from that person. We feel it's our duty to warn the country about the danger of this president. If we think we have learned something about Donald Trump and his psychology that is dangerous to the country, yes, we have an obligation to say so.

There's more and more recognition that a carbon economy is dangerous to us economically. And there is increasing recognition that renewable fuels have economic value as well as obvious value for our health and our well-being and our survival. In fact, as you know, the economic revolution in renewable fuels has been impressive. It really had not been anticipated.

I don't have the feeling that as a very young person I read books that absolutely made their mark on my mind.

With the nuclear threat we know that if sufficient weapons are used, human civilization - all of humankind - could be extinguished literally by "nuclear winter." So we have to see ourselves as part of the ultimate human group, just as we have to do with global warming.

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.