The Greatest Question Ever Asked?

We’ve been doing a lot of media interviews for SuperFreakonomics, and once in a while you get asked a really interesting question.
But I don’t think this one will ever be topped. It comes from a journalist in India:

You state that your book is based on one fundamental assumption about human nature: people respond to incentives. Which is another way of saying that people are basically selfish. Take someone like Jesus Christ. What was his “incentive” to go on the cross?

This question made me think in about 10 directions at once. It also made me want to grab a New Testament and read it in an entirely new way. For starters, here’s an interesting blog post titled “The Economics of Jesus” which begins with this excellent line: “Jesus probably didn’t know much about macroeconomics, even though he was God.”
By the way, I haven’t yet answered this journalist’s question — it’s an e-mail Q&A interview — so I’m eager for your input.