Via Kathryn Jean Lopez, an exchange between a Unitarian minister and Christopher Hitchens:

[Unitarian;] The religion you cite in your book is generally the fundamentalist faith of various kinds. I’m a liberal Christian, and I don’t take the stories from the scripture literally. I don’t believe in the doctrine of atonement (that Jesus died for our sins, for example). Do you make and distinction between fundamentalist faith and liberal religion?
[Hitch]: I would say that if you don’t believe that Jesus of Nazareth was the Christ and Messiah, and that he rose again from the dead and by his sacrifice our sins are forgiven, you’re really not in any meaningful sense a Christian.

He’s right, of course. Now, I bring this up not for purposes of a culture-war exchange of fire, but to instigate a theological discussion around the following question: How much do you have to believe to qualify as a Christian?
Earlier this month, I was at a dinner in which the issue of religious orthodoxy came up in discussion. Someone at the table made essentially the same point as this Unitarian minister, saying that there were plenty of Christians — he even cited the Unitarians — who don’t believe in core doctrines of Christianity. He suggested that the only reason they are seen as non-Christians is politics, cultural and otherwise.
I think this is quite wrong, but a common way of thinking about religion among moderns. The dividing line is not really between “liberals” and “conservatives” in Christianity or any other religion. After all, one can be a perfectly orthodox Christian and profess socialism as a political doctrine. No, the real line is between those who believe that religion makes statements about the the world as it is, and those who believe religion makes statements about the values and inner life of those who profess it. In other words, does religion provide an objective account of reality, or is it an expression of the subjective preferences of the person who professes it?
This is why I have more in common with a gruff unbeliever like Hitch than I do with people who profess religion but reduce it to pudding. Mind you, I don’t believe that my religion, or any religion, contains the entirety of what there is to know about the world. This is why I favor genuine ecumenical dialogue, approached with a true willingness to learn from the experiences of others. But that’s possible to carry out without being a complete relativist. In other words, I may be a believing Christian, who really does believe that the God of Abraham, Isaac and Jacob incarnated as a Nazarene Jew in first century Palestine, and who died on a cross, rose from the dead, ascended to heaven, the whole megillah … and still believe I have something to learn from Jews, Muslims, Taoists, atheists, and just about everyone about truth, and the meaning and nature of life.