Often, the way Timothy Keller articulates the gospel (and the implications of the gospel) in his new book–The Reason for God— are incredibly thought-provoking. Take this one for example,
“A central message of the Bible is that we can only have a relationship with God by sheer grace. Our moral efforts are too feeble and falsely motivated to ever merit salvation. Jesus, through his death and resurrection, has provided salvation for us, which we receive as a gift. All churches believe this in one form or another. Growth in character and change in behavior occur in a gradual process after a person becomes a Christian. The mistaken belief that a person must ‘clean up’ his or her own life in order to merit God’s presence is not Christianity. This means, though, that the church will be filled with immature and broken people who still have a long way to go emotionally, morally, and spiritually. As the saying has it: ‘The church is a hospital for sinners, not a museum for saints.’
… Now imagine that someone with a very broken past becomes a Christian and her character improves significantly over what is was. Nevertheless, she still may be less secure and self-disciplined than someone who is so well adjusted that she feels no particular need for religious affiliation at all. Suppose you meet both of these women the same week. Unless you know the starting points and life journeys of each woman, you could easily conclude that Christianity isn’t worth much, and that Christians are inconsistent with their own high standards. It is often the case that people whose lives have been harder and who are ‘lower on the character scale’ are more likely to recognize their need for God and turn to Christianity. So we should expect that many Christians’ lives would not compare well to those of the nonreligious (just as the health of people in the hospital is comparatively worse than people visiting museums).”
-Timothy Keller, The Reason For God (Dutton: 2008), pp. 53-54.