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.

The happy ending of the Resurrection is so enormous that it swallows up even the sorrow of the Cross.

[T]he main problem in life is sin, and the only solution is God and his grace. The alternative to this view is to identify something besides sin as the main problem with the world and something besides God as the main remedy. That demonizes something that is not completely bad, and makes an idol out of something that cannot be the ultimate good.

Christ will do everything for you or nothing. He's either all of your righteousness or none.

Love is primarily giving. It’s an action that leads to a feeling, not a feeling first.

Money isn't an idol. It just shows you where your idols are.

If you love anything in this world more than God, you will crush that object under the weight of your expectations.