Just before Christmas, a new cafe opened up outside the main gates of the University of Arizona. The coffee is good and it’s a shorter walk than the alternatives. The people are friendly, too. One of my colleagues was chatting with the owner, Danny, last week—he’s often behind the bar serving customers. Danny asked whether my friend taught at the university, and then in what department. “Sociology,” my friend said, which is usually enough to move the conversation to some other topic. But instead Danny said “Oh, my uncle was a sociologist—he was pretty well known in Europe years ago, but you’ve probably never heard of him. “What was his name?” asked my friend. “Oh, Mannheim,” says the owner. ”Karl Mannheim?!” says my friend. “Wow, you know his first name!” says Danny. Small world. Sociologists know that already, but the point of that insight is precisely that you don’t know about every case. There are probably other connections of this sort in my acquaintance network that I’m completely unaware of. Yours, too.