I got to teach Episcopal Sunday school last week, a rare privilege, and it was in a New York church so the kids had plenty to say. Teenagers, and if you expect them to sit in rapt silence as you tick off points of theology, you're in the wrong place. They made plenty of noise, and not much of it about religion. Some of them seemed to be on a faith journey that was heading away from the Nicene Creed toward something cooler and jokier, some form of animism perhaps, the worship of cougars and badgers.

I like teenage noise. (It's the quiet brooders like me you have to worry about, right?) They let me say my piece — God prefers honest doubt to false piety — and then they said their pieces, and what shone through was a sensible anxiety about the future and the fact that they care a lot about each other. You could imagine a confirmed agnostic hanging out here just for the warmth and conversation.

We sat in a sort of triangle, two couches at a right angle, a line of chairs, a window looking out at the snow on Amsterdam Avenue, and talked about the rather improbable notion that God sent Himself to Earth in human form, impregnating a virgin who, along with her confused fianci, journeyed to Bethlehem where no rooms were available at the inn (it was the holidays, after all), and so God was born in a stable, wrapped in cloths and laid in a feed trough and worshipped by shepherds summoned by angels and by Eastern dignitaries who had followed a star.

This magical story is a cornerstone of the Christian faith and I am sorry if it's a big hurdle for the skeptical young. It is to the Church what his Kryptonian heritage was to Clark Kent — it enables us to stop speeding locomotives and leap tall buildings at a single bound, and also to love our neighbors as ourselves. Without the Nativity, we become a sort of lecture series and coffee club, with not very good coffee and sort of aimless lectures.

On Christmas Eve, the snow on the ground, the stars in the sky, the spruce tree glittering with beloved ornaments, we stand in the dimness and sing about the silent holy night and tears come to our eyes and the vast invisible forces of Christmas stir in the world. Skeptics, stand back. Hush. Hark. There is much in this world that doubt cannot explain.

(I might have told the kids that when you use the word "awesome" to describe everything above mediocre, you're missing a word for Christmas Eve, but I'm not their editor either.)

New York is very gaudy at Christmas, and the Santa Clauses on Fifth Avenue swing their bells with style, and the store windows glimmer and the city at dusk is ever magical, but all New Yorkers know that loneliness is a part of life and can't be extinguished, not by entertainment or pharmaceuticals.

I walked around the city that Sunday night — two homeless people were camped on the steps of a Lutheran church on 65th, in the midst of grand old apartment buildings, and the opera crowd was wending toward Picholine and the Cafi des Artistes for the lobster bisque, and on the uptown subway we all sat and did not stare at the crazy old man boogeying in his sleeveless t-shirt and singing incoherently and watching his own reflection in the glass — and how 17-year-old kids should mesh New York with the Nativity, I was not able to tell them. God prefers admitted incompetence to fake authority.

But explaining the universe to them was not my job, only to love them, which I do, utterly. They are brave and loyal and funny, heading out into a world that is not forgiving of mistakes, that will try to pummel them into submission, that is capable of awesome cruelty and deceit, but here they are. Emily Dickinson said, "To live is so startling it leaves little time for anything else," and if she, who spent most of her adult life in her bedroom, could feel that way, then think how it must be for the rest of us.

A day in New York can show you such startling sights, including a band of doubting teenagers clustered in church on a snowy morning, that the birth of the child in the hay seems not so impossible after all, even appropriate, even necessary.

Garrison Keillor's "A Prairie Home Companion" airs from 6 to 8 p.m., on Saturdays on KHPR FM 88.1 and on Sundays on KIPO FM 89.3 His column appears Wednesday at www.honoluluadvertiser.com/opinion and in Sunday's Focus section.