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.

By exploring the political and moral colorings of discoveries about what makes us tick, we can have a more honest science and a less fearful intellectual milieu.

Violent movements attract thugs and firebrands who enjoy the mayhem. Violent tactics provide a pretext for retaliation by the enemy and alienate third parties who might otherwise support the movement.

America had, for one thing, lived in anarchy for - until much more recently than Europe. We had the Wild West, where the cliche of the cowboy movies was the nearest sheriff is 90 miles away, and so you had to pack a gun and defend yourself.

For one thing, before the 20th century, there were plenty of genocides. We tend to forget about them, partly because they weren't as well documented and partly because, until recently, people didn't care. We used euphemisms like 'sackings' and 'sieges' instead of calling them 'genocides.'

An ideology can provide a satisfying narrative that explains chaotic events and collective misfortunes in a way that flatters the virtue and competence of believers, while being vague or conspiratorial enough to withstand skeptical scrutiny.

What is true for the emotions may also be true for the intellect. Some of our perplexities may come from a mismatch between the purposes for which our cognitive faculties evolved and the purposes to which we put them today.