«Peter Pan»

You see, Wendy, when the first baby laughed for the first time, the laugh broke into a thousand pieces and they all went skipping about and that was the beginning of fairies. And now when every new baby is born, its first laugh becomes a fairy. So there ought to be one fairy for every boy and girl.

Children know such a lot now. Soon, they don't believe in fairies. And every time a child says, "I don't believe in fairies," there's a fairy somewhere that falls down dead.