John Piper was recently challenged to speak to a group of people who don't necessarily agree with him theologically. He presented seven theses on why he is on this planet. I particularly like his third:
I press on this because I believe that if we are God-centered simply because we consciously or unconsciously believe God is man-centered, then our God-centeredness is in reality man-centeredness. Teaching God’s God-centeredness forces this issue of whether we treasure God because of his excellence or mainly because he endorses ours.