The 9/11 strikes left an indelible impact on our minds, but in relative terms, the scale of casualties actually wasn't all that high.

You have to remember that not every creature that was evolving left behind its skull or its tools for our convenience tens of thousands of years later. Most bones or most tools rot or get buried and are never found again.

So no, it's not all in the genes, but what isn't in the genes isn't in the family environment either. It can't be explained in terms of the overall personalities or the child-rearing practices of parents.

For all the tribulations in our lives, for all the troubles that remain in the world, the decline of violence is an accomplishment that we can savor - and an impetus to cherish the forces of civilization and enlightenment that made it possible.

Climate change could produce a lot of misery and waste without necessarily leading to large-scale armed conflict, which depends more on ideology and bad governance than on resource scarcity.

I'm very interested in language because it reflects our obsessions and ways of conceptualising the world.