Greg Gilbert looks carefully at how we define the gospel: part 1, part 2, part 3. I think it’s very helpful.
Here’s a summary:
I think we can get at an answer to all those questions by realizing that the Gospel of the Cross (that is, the narrow sense of “gospel”) is not just any part of the Gospel of the Kingdom (that is, the broad sense of “gospel”).* Rather, the gospel of the cross is the gateway, the fountainhead, even the seed, so to speak, of the gospel of the kingdom. Read the whole NT, and you quickly realize that its univocal message is that a person cannot get to those broad blessings of the Kingdom except by being forgiven of sin through the death of Christ. That is the fountain from which all the rest springs.
The implications which flow from this are:
First, it’s worth saying again: Those who argue that “the gospel” is the declaration of the kingdom are simply wrong. The gospel is not the declaration of the kingdom. It is (in the broad sense) the declaration of the kingdom together with the means of entering it. Second, to say that the Gospel of the Cross (that is, the narrow) is somehow not the gospel, or less than the gospel, is wrong. So long as the question is, “What is the message a person must believe to be saved,” the gospel of the cross is the gospel. (See the first post in this series.) Jesus, Paul, and Peter say so.** Third, to say that the Gospel of the Kingdom (that is, the broader, which includes the gospel of the cross) is somehow gospel-plus, or a distraction from the real gospel, is also wrong. So long as the question is “What is the whole good news of Christianity,” the gospel of the kingdom is not gospel-plus; it is the gospel. Jesus, Paul, and Peter say so. Fourth, it is wrong to call a person a Christian simply because they are doing good things and “following Jesus’ example.” To be a Christian, to be a partaker of the blessings of the Kingdom, requires one first to go through the gate—that is, to come to Christ in faith and be forgiven of sin and atoned for. Bunyan tells the story in Pilgrim’s Progress about the characters Mr. Formalist and Mr. Hypocrisy whom Christian meets on the path to the Celestial City. After a moment’s conversation, however, Christian realizes that they had jumped the wall to the path rather than going through the Wicket Gate. The upshot: These two are not Christians, regardless of how well they are now navigating the path. To change the characters a bit, there are many people out there (hello emergent church!) who need to realize that Mr. Jesus-Follower and Mrs. Kingdom-Life-Liver are not Christians—not unless they’ve come to the crucified Jesus in repentance and faith for the forgiveness of their sins. A person can “live like Jesus lived” all he wants to, but unless he goes through the Wicket Gate of atonement, faith and repentance, he’s not really come to Christ. He’s simply jumped the wall. Fifth, I believe it is wrong ever to say that non-Christians are doing “kingdom work.” A non-Christian working for human reconciliation or justice is doing a good thing; but that is not Kingdom work because it is not done in the name of the King. C.S. Lewis was wrong; you can’t do good things in the name of Tash and expect Aslan to be happy about it. Sixth, the ultimate goal of any mercy ministry—whether done by an individual Christian or a church—has to be to point the world back to the gate. There’s much that could be said here, but I think understanding all this rightly can provide a powerful missionary motive and a penetrating witness to the world. When you renovate a barber shop in the name of Jesus, for instance, you need to tell the owner (to put it sharply since I’m not actually talking to the guy right now), “Look, I’m doing this because I serve a God who cares about things like beauty and order and peace. In fact, the Bible says and I believe that God is one day going to recreate this world and inaugurate a kingdom where paint won’t peel and trees won’t die. But [and here we get to the point] I don’t think you’re going to be a part of that. Because of your sin. Unless you repent and believe in Christ.” And then you tell him the good news of the cross. If you just renovate the barber shop and proclaim the coming kingdom, you’ve messed up. The gospel of the kingdom is the declaration of the kingdom together with the means of getting into it. Seventh, as I’ve argued before, I believe that many in the emergent church—for all their insistence about how astonishing and surprising their gospel is—have missed entirely what really is astonishing about the gospel. That Jesus is king and has inaugurated a kingdom of love and compassion is not really all that astonishing at all. Every Jew knew that was going to happen someday. What is truly astonishing about the gospel is that the Messianic King dies to save his people—that the divine Son of Man in Daniel, the Messiah, and the Suffering Servant in Isaiah turn out to be the same man. That, moreover, is ultimately how we tie together the Gospel of the Kingdom and the Gospel of the Cross. Jesus is not just King, but Crucified King. Next to that, what many in the emergent church are holding out as an astonishing gospel is not astonishing at all. It’s just boring. Eighth, everything we’ve said so far drives toward the conclusion that evangelistic, missiological, and pastoral emphasis in this age belongs on the gospel of the cross—on the fountainhead, the gateway of the broader gospel of the kingdom. That’s because all the rest is unattainable and indeed bad news unless we point people there. Not only so, but this is the age in which God’s overarching command to every human in the world is “Repent and believe.” There’s only one command that is actually included in the gospel itself (whether broad or narrow): Repent and believe. That is the primary obligation on human beings in this age, and therefore it must be our primary emphasis in our preaching, too.