Lyle Schaller denies he's a prophet. I'm not sure I believe him. He's at least a world-class tracker—reading footprints, sniffing the air, seeing what others miss. And when he tells you what you're going to find over the next ridge, I've learned you'd better pay attention!

Lyle is an author (more than 30 of his books are still in print), a former city planner, and perhaps this generation's best analyst of church sociology.

He's also a neighbor. A few weeks ago, Eric Reed and Drew Zahn and I drove down Naperville Road to pay Lyle a visit. His living room was jammed with boxes and files that he was cleaning out at his wife's request. ("We've been married 20,209 days," he told us with typical deadpan. "If you keep track of it this way, every day is your wedding anniversary," which tells you something about the way his mind works.)

We asked him what cultural trend will most significantly impact the way churches do ministry in the next few years.

"The changing definition and configurations of 'family,'" ...