When we meet Jesus of Nazareth at the beginning of the Gospel of Mark, almost surely the oldest of the four, he’s a full-grown man. He comes down from Galilee, meets John, an ascetic desert hermit who lives on locusts and wild honey, and is baptized by him in the River Jordan. If one thing seems nearly certain to the people who read and study the Gospels for a living, it’s that this really happened: John the Baptizer—as some like to call him, to give a better sense of the original Greek’s flat-footed active form—baptized Jesus. They believe it because it seems so unlikely, so at odds with the idea that Jesus always played the star in his own show: why would anyone have said it if it weren’t true?