There is nothing like taking part in a worship service with 17,000 people. If you are surrounded by a choir that large, all of the hymns sound in tune. With that many people gathered to pray in the same place at the same time, you have no doubt God will hear somebody in the crowd. And when a super-charged speaker stands up to challenge people to follow the commandments of Christ, the group dynamics of such a huge crowd ensure that someone, somewhere, is ready to answer the challenge.

That was the case in December 1979, at a mission conference in Urbana, Illinois. Mobs of college students descended upon the campus of the University of Illinois during Christmas break. They came in chartered buses and Volkswagen vans. Every morning was filled with Bible study, prayer, and singing. Each night…