Several contributors collaborated recently on a new book called Don't Call It a Comeback: The Old Faith for a New Day. This week the book's editor, Kevin DeYoung, asked if several of us would answer a quick question related to our respective topics, and posted them over at his blog. Here's the question and my answer about my chapter on the kingdom of God.

The kingdom is a huge theme in the Bible, and yet it can be difficult to define. How would you explain the kingdom of God to a 15-year-old?

Sometimes even those who've followed Jesus for a long time find the kingdom message a difficult one to grasp. We sometimes assume "kingdom" is just a metaphor for "getting saved" or for another denominational program or political crusade. We hear chatter all around us about the Prince of Wales or the local high school homecoming queen or the advertising slogans of the "King of Beers" or the "Dairy Queen."

Against this kind of potential confusion, the mission of Christ starts and ends not just in the announcement of forgiveness of sins or in the removal of condemnation—although both of those things are certainly true. The mission of Christ starts and ends with an announcement that God has made Jesus emperor of the cosmos—and he plans to bend the cosmos to fit Jesus' agenda, not the other way around.

The kingdom of God, then, is the good news that the right rule of God, and the right rule of man—a rule our ancestors Adam and Eve lost—have come together in the right rule of one right God-man: Jesus of Nazareth. In his sin-resisting life, his wisdom-saturated teaching, his demon-exorcising power, his substitutionary, conquering death, and his justifying, victorious resurrection, Christ is king.

That king, through his Spirit, invites all men to believe by faith what they'll someday see by sight—what everyone will someday see by sight: Jesus is Lord. Jesus forgives. Jesus is king. And his reign will extend to the corner of every galaxy, forever.