For students of religion, often a separate set from the solely religious, the nativity of Jesus is a moment to reflect on the history of Christian belief. Every age, beginning with the primitive one of Caesar's Judea to today's global Babel, has projected a different Jesus. It would take a miracle to add up accurately add up the number of Christs wandering around in the pages of religion's history.

It was so in the beginning. The infancy narratives of Matthew and Luke demand an immediate act of faith similar to that which readers of a modern newspaper must make: these reporters are telling it straight. In major facts and minor details, Matthew and Luke tell it differently.

Matthew presents Jesus who is persecuted at birth: ''Herod will seek the child to destroy him,'' an angel says to Joseph in a dream. The stepfather flees with his family by night to Egypt, while Herod organizes the Christian era's first death squad. Matthew says nothing on how Joseph, Mary and Jesus survived. Did they sell the gold, frankincense and myrrh the eastern visitors had given? How old was Jesus when his parents, heeding another dream, returned to Galilee?

Specifics are left hanging by Matthew, a former tax collector who wrote in Aramaic, not the Greek common to the rest of scripture. Despite that, his gospel is both a warning and an invitation to the Palestinians for whom it is written: Christianity, from its first hours in Bethlehem, will be a costly religion. Its founder was no more than newly born when the state wanted him executed.

The terror has remained. Herodian governments of the 20th century have been murdering Christian lay people and clergy in every land from El Salvador to Poland.

In Luke, a different Jesus is presented -- Christ as a voluntary outcast. He is born in a stable, not a house as in Matthew. Gift-bearing wise men from the East don't come, only local shepherds. Instead of fleeing to Egypt, the family returns home peacefully. Joseph isn't poor. He has money to pay for a room at the inn, except it is filled.

The message of Luke's nativity is that Christianity involves simplicity and humility. These are often the rarest of Christian virtues, but without them the words of justice and peace are impossible.

As with any world religion, Christianity offers options on how to live. Not many adherents, in fact, do live this religion: Gandhi of India, a Hindu who studied the gospels, was asked what he thought of Christianity. He replied that he was still waiting to meet his first Christian. Nietzsche had a similar thought: history has seen only one Christian, Christ.

The Aramaic-speaking Jesus of Judea, with the details of his birth not accurately known, is not the Jesus of 20th-century institutions that call themselves, through dogmas, hierarchies and membership rolls, the Christian church. Instead, the persecuted and the risk-taking Jesus of Matthew and Luke is at the core of this religion. Scholars not a part of it often understand better than Christians the need to study the life and message of Christ.

Martin Buber, the Jewish theologian, wrote: ''From my youth on, I have felt that Jesus was my elder brother. That Christianity has regarded and still does regard him as God and redeemer has always appeared to me a matter of the utmost seriousness, which for his sake and for mine, I must try to comprehend.''

Such a sentiment exemplifies the study of religion at its purest. To celebrate Christmas without reexploring the mystery of its origin is to miss the joy of the season. It's the joy of reflecting, of seeing religion as faith and not ideology, and then looking within to see what you're willing to pay or risk to put belief into action.