I've heard plenty of Christians try to answer the why question by going back to the what. "You have to believe because Jesus is the Son of God." But that's answering the why with more what. Increasingly we live in a time in which you can't avoid the why question. Just giving the what (for example, a vivid gospel presentation) worked in the days when the cultural institutions created an environment in which Christianity just felt true or at least honorable. But in a post-Christendom society, in the marketplace of ideas, you have to explain why this is true, or people will just dismiss it.
Timothy KellerIn Ephesians 5, Paul shows us that even on earth Jesus did not use his power to oppress us but sacrificed everything to bring us into union with him. And this takes us beyond the philosophical to the personal and the practical. If God had the gospel of Jesus's salvation in mind when he established marriage, then marriage only 'works' to the degree that approximates the pattern of God's self-giving love in Christ.
Timothy KellerOur character is mainly shaped by our primary social community - the people with whom we eat, play, converse, and study.
Timothy KellerSuccess and suffering will either darken your heart or make you wise, but they won't leave you where you were.
Timothy Keller