[L]ike people, ideas have social lives. They’re one way when they’re by themselves, and another when they’re surrounded by their peers. Crammed together, they grow more uncertain, more interesting, more surprising; they come out of themselves and grow more appealing, and funnier. You wouldn’t want all of intellectual life to be that social--we couldn’t make progress that way. But there’s a special atmosphere that develops whenever truly different ideas congregate, and, on the whole, it’s too rare.