The Ur-Luke

In the course of a discussion about whether the pervasiveness of religious belief bears on its truth:

it is astonishing how much convergence there is in folk belief

No, it's not. It's no more astonishing than the incredible number of folk cultures that use the pentatonic scale, or the incredible number of cultures that have a myth in which a farm boy living with adoptive parents encounters a mysterious figure who explains to him that he is the true son of the High King and must battle the Dark Lord to save the realm. Does that mean that there really IS a farm boy who is the true son of the High King? No. It means that everybody has some similar built-in ideas about what makes a good story.