George Kennan is another extreme case. He was the American consul in Berlin until the war between Germany and the United States broke out in December 1941. And until then he was writing pretty supportive statements back stressing that we shouldn't be so hard on the Nazis if they were doing something we didn't agree with - basically repeating the idea that they were people we could do business with.

Today's Democrats are pretty much what used to be called moderate Republicans a generation ago.

There's something deeply rooted in American culture. You can pretty much identify what it was. You take a look at the history. It was internal conquest. You had to defend yourself against what the Declaration of Independence, Thomas Jefferson, an enlightened figure, called the attacks of the "merciless Indian savages," whose known way of warfare was torture and destruction. Also you had a slave population, you had to protect yourself against them. You needed guns.

In the Munich agreement in late 1938 [Franklin] Roosevelt sent his chief adviser Sumner Welles, who came back with a very supportive statement saying that Hitler was someone we could really do business with and so on.

I remember talking to, 40 years ago, one of the leading people in the government who was involved in arms control, pressing for arms control measures, détente, and so on. He's very high up, and we were talking about whether arms control could succeed. And only partially as a joke he said, "Well it might succeed if the high tech industry makes more profit from arms control than it can make from weapons-related research and production. If we get to that tipping point maybe arms control will work." He was partially joking but there's a truth that lies behind it.

Language etches the grooves through which your thoughts must flow.

I am thinking of actual cases of adolescents, lets say, who think they have five hundred friends, because there are five hundred people on their Facebook account. But these are the kind of friends whose relation to you is that if you say 'I bought a sandwich'; they say 'did it taste good?' You know, that's a kind of interaction, but very different to having a real friend, somebody who you can actually talk to.