Two pastors serving youthful congregations in big cities, long the statistical capitals of secular culture, say they must talk about sin to be true to their calling. They just have to use 21st-century lingo.

Tim Keller of Redeemer Presbyterian Church in Manhattan is a modern-day variation of the circuit-riding preacher. He dashes across Central Park to three different leased locations to serve 5,000 worshipers at five services on Sundays.

When Keller, author of The Reason for God: Belief in an Age of Skepticism, speaks about "sin" to his audiences, which are 70% single and younger than 40, "I use it with lots and lots of explanation, because the word is essentially obsolete.

"They do get the idea of branding, of taking a word or term and filling it with your own content, so I have to rebrand the word 'sin,' " Keller says.

"Around here it means self-centeredness, the acorn from which it all grows. Individually, that means 'I live for myself, for my own glory and happiness, and I'll work for your happiness if it helps me.' Communally, self-centeredness is destroying peace and justice in the world, tearing the net of interwovenness, the fabric of humanity."

Mark Driscoll says a little talk of hellfire, so out of fashion these days, would do the world good.

Driscoll founded Mars Hill Church in Seattle, a non-denominational megachurch with 7,000 in Sunday attendance, chiefly singles in their 20s.

He defines sin as "anything contrary to God's will. People assume the way they are is normal, not that something has gone terribly wrong, and this world is abnormal."

Although his primary audience is newbie Christians, Driscoll is sharply clear: "Without an idea of sin, Easter is meaningless."