No surprise that as the ranks of the religiously unaffiliated grow, so do the numbers of those who don't believe in the historicity of the Nativity accounts in the Bible -- virgin birth, angels, wise men, star, etc.

What may be more surprising is that doubters of the Nativity details are growing even in church circles.

I wrote about the survey in today's Post-Gazette (I'll post an exact link when I get it), asking pastors how they prepare their Christmas sermons for audiences that may be more skeptical than in the past. Those I talked to didn't seem too worried about it. Even those affirming all the historical details said they weren't using the Christmas pulpit as debating forum.

But clergy are going to have to take note of the fact that even their own flocks are more open to interpreting such stories symbolically than literally.

Public Religion Research Institute says 49 percent of Americans believe in its historicity -- down from 67 percent a decade ago -- and 40 percent see them as stories illustrating theological truths.

Roman Catholics' belief in the literal Nativity dropped from 72 to 51 percent. It was down 10 points among racial minorities who are Protestants and down 12 percent among white evangelical Protestants, although huge majorities among both those groups still believe. Among mainline Protestants, 56 percent of whom say the accounts are historical, the results haven't budged since 2004.

A renowned Roman Catholic biblical scholar, the Rev. Raymond Brown, wrote in his massive study of the narratives that it's ironic that seminaries spend relatively little time on the Nativity -- since preaching about it is one of the most important pulpit tasks of a pastor's year.

There's ongoing debate among Christians over whether someone has to believe these details to be a Christian or to believe in essentials of the faith.

Brown writes:

"Whether or not the infancy narratives were historical, whether or not they were based on eye-witness testimony, whether or not they had a pre-Gospel existence, Matthew and Luke thought they were appropriate introductions to the career and significance of Jesus. ... From this point of view the infancy narratives are not an embarrassment but a masterpiece."

Pope Emeritus Benedict XVI, in his recent book on the birth of Jesus, said it is important to separate the Christian story, rooted in history, with the pagan legends of vague origin: "It was not with the timelessness of myth that Jesus came to be born among us. He belongs to a time that can be precisely dated and a geographical location that is precisely defined. ... God intervenes directly in the material world. … God is God and he does not operate merely on the level of ideas."

Photo is of the Pittsburgh Creche