Clue: Neither does Rick Warren. THAT IS OUR PROBLEM TOO.
If you would like a step by step analysis of what is wrong with Rick Warren's teachings, I suggest you go here and listen to the interview of Warren Smith:
Mike Corley interviews Warren Smith
Or here and read some Biblical Critiques:
That should help you figure out what is Christian that Rick Warren refuses to define.
Rick Warren is just another (more widely successful) pusher of the Church Growth Movement fad which is unBiblical.
Thanks for your opinions.