A caller to the radio program about a month ago asked about answering a historical challenge to Luke 2 that Bart Ehrman has raised. I have to confess, I wasn't aware of this apparent problem, and researching it has actually been quite fascinating. Ehrman mentions it in this week's Newsweek magazine. Part of the key to the answer is what the Greek text of Luke 2 actually says, as opposed to what we've come to think it says. Greg has observed that answering many of the problems about the Bible that callers raise on the radio program can be resolved simply by reading the text. That's part of the answer here, plus a little historical context.
The gist of the problem is that Luke claims that the first tax when Quirinius was governor of Syria was at the time of Jesus' birth – around 4-2 B.C. The Jewish historian Josephus, however, records that the first tax under Quirinius' administration was in 6 A.D., after Jesus' birth. There's no reconciling these reports, unless we actually look back at what Luke wrote and at some historical data.
First let me make the point Greg made to the caller. Luke himself is a historical account that we should take just as seriously as Josephus. The posture that the Bible is the questionable source behind other historical sources is just plain prejudice before examining the accounts. The Gospels, just like Josephus, claim to be ancient historical records, and they should be taken as such until proven to be untrustworthy. So far, they have not been dismissed based on the facts, only by assumption. Josephus' accuracy can be questioned in light of Luke's account just as much as the other way around.
As it turns out, the two historical sources are easily reconciled. And a quick note on answering apparent contradictions in the Bible: Reason requires we show a possible resolution, not that we have proof that it's the actual resolution. If there's a way to understand the text in harmony with other historical data, then we've answered the challenge. That's true for any historical document, not just the Bible.
Go and read Luke 2 in the ESV or NASB – no tax is mentioned, only a registration or census. I would have recited Luke 2 from memory "that all the world should be taxed." That's in the KJV, but it's not what Luke actually wrote. Luke doesn't mention the purpose for the registration. We know from historical records that there were other reasons the rulers ordered registrations of their citizens, and that Augustus ordered citizens to register on more than one occasion. Tertullian reports that there were censuses conducted in Palestine during the time period Jesus was born. So we have historical support that registrations were conducted at that time.
It could be that the registration was for the purpose of renewing loyalty to Caesar on the 25th anniversary of the Roman Senate giving Augustus complete allegiance. As descendants of a royal family, both Mary and Joseph would have been required to go to the seat of their royal ancestor. Both had royal blood, so both had to be registered in Bethlehem.
In fact, Josephus reports an oath of loyalty took place at the time of King Herod. It fits perfectly with what Luke actually wrote.
The other apparent problem with Luke's account is the description of Quirinius as governor of Syria, but other historical records show that others were governor during the time of Jesus' birth. And Josephus mentions that Quirinius was governor in 6 A.D., not at the time of Jesus' birth. However, Justin Martyr recorded that Quirinius was procurator in Judea during the time of Saturninus, who was governor of Syria. Justin Martyr adds that this was during the time of Jesus' birth and that Quirinius was there for the purpose of conducting a census. Gleason Archer explains that Quirinius was a special assistant to Augustus who often sent him on his behalf to conduct specific tasks. To the provincial citizens, procurators had authority just as the governors had. From a functional standpoint, there wasn't any real difference between the offices. But from what I've read (I don't know Greek), what Luke wrote means ruling or administrating; it doesn't have to mean govern or governor, though it can. (The Greek can also be translated before Quirinius was governor of Syria, which would reconcile the timing and position, as well.)
So an appeal to what Luke actually wrote and some historical records reconcile this apparent problem. Luke said that he set out to write a careful historical account of what took place. And there's very good reason to think that is what he accomplished.