Why did Jesus have to die?
Here's an interesting article on the atonement from Time Magazine that was written in the wake of Mel Gibson's Passion of the Christ. The takeaway point is that Christians have always disagreed among themselves about the exact nature of the atonement, the 'divine calculus' (as the article puts it) behind Jesus' death. And when ordinary Christians affirm that Jesus 'died for our sins', they often have very different ideas implicit in that one affirmation. This is not to say that different atonement models cannot be synthesized, but it does cast doubt on the idea that there is one core understanding of the atonement that is essential to true Christian piety.