Now moving on to a possible second chapter to The Essential Jesus, this one titled, "The Kingdom of God."
Our God Reigns
What was Jesus' ministry on earth all about? What did he say to the crowds? What did he teach? Matthew, Mark, and Luke all agree that his key message was the good news of the kingdom of God.  This is the message he brought to the crowds on the Galilean countryside. 
But what did he mean when he said that, "The time is fulfilled, and the kingdom of God has come near; repent, and believe in the good news" (Mark 1:15, NRSV)? Again, all four gospels locate the beginning of Jesus' earthly mission in the preaching of John the Baptist. Since Jesus was baptized by John, we can assume he also was 1) looking for the restoration of God's people, Israel, 2) that he agreed with the call of Israel to repentance and the symbolic washing away of sins in baptism in preparation for 3) the arrival of the anointed one, the messiah and 4) the judgment of sinners, at least within Israel.
Thus the gospels explicitly remember Jesus preaching repentance and commitment to this "good news," similar to what the Baptist was calling Israel to do. Against this backdrop, the kingdom of God must have referred to this coming, restored people of God. The kingdom of God, of course, locates God as the king over this renewed people. But we can also assume that a messiah would be part of this kingdom. The Jews of the day would have assumed that an earthly king would reign over the kingdom as God's representative on earth.
The prayer Jesus taught gives us a key insight into at least part of what he meant when he spoke of God's kingdom coming: "Your kingdom come. Your will be done, on earth as it is in heaven" (Matt. 6:10). For God's kingdom to come was for God to rule the earth as he does the heaven. No doubt the idea of God's rule returning to the earth involved more than one layer in Jesus' message. For most in the crowds, they would have surely heard the return of Israel's sovereignty and political independence as a people. For Jesus, as we will see, it also involved the defeat of demonic forces that God had allowed to run rampant in the land.
With the word "gospel" and the idea of the reign of God right next to each other, it seems overwhelmingly likely that Isaiah 52:7 stands in the background of Jesus' message:
"How beautiful upon the mountains are the feet of the messenger who announces peace, who brings good news, who announces salvation, who says to Zion, “Your God reigns.”
To be sure, the gospels are in Greek and Jesus would not have been using the Greek Old Testament. But the collection of images and language fits the historical context so well that it seems likely we are hearing in the gospels a Greek version of a message that goes back to Jesus.
For example, just as Isaiah 40 which was used of John the Baptist, Isaiah 52 also comes from the context of Israel's return from captivity in Babylon. Since Jesus' ministry flowed out of the ministry of John the Baptist, since this imagery of restoration and returning from exile was part of John's message, since experts overwhelmingly agree that the kingdom of God stood at the heart of Jesus' message, we are surely safe to think that Isaiah 52:7 was ground zero of Jesus' earthly preaching. When the message moved into Greek speaking territory, surely the word "gospel" leaped from the page of Greek Isaiah.
In the Roman Empire, a gospel was good news of an extraordinary sort, such as the birth of an heir to the throne or a major military victory. The Roman Emperor Augustus is celebrated in one inscription as savior of the world and his birth was the beginning of a gospel for the world.  Jesus and the earliest Aramaic speaking Christians may not have used the word in this way, but we can make a good argument that the idea started in Jesus' use of Isaiah and that the word "gospel" took off as soon as the message hit Greek speaking believers.
It thus also seems likely that the phrase "the kingdom of God" also comes directly from Isaiah 52:7 and the idea that in the restoration of Israel, God will reign once more. The kingdom of God is the fact that "our God reigns," once more on earth as it is in heaven. If John's message was one of anticipation and preparation, Jesus' message was one of arrival. The kingdom of God is imminent, about to embark in full. It is beginning and growing.
 Matthew's "kingdom of heaven" is not something different but a matter of Matthew's style. Following the dominant assumption that Matthew used Mark as a starting point, then Matthew at a number of points intentionally changes Mark's "kingdom of God" to "kingdom of heaven," indicating that the phrasing comes more from Matthew than from Jesus himself. Some think it was a reverential move on his part, to refer to the place where God is rather than to God directly. The theory is not without problems, but is perhaps the best one out there.
 Key summaries of Jesus' message in all three of the "Synoptic" gospels summarize Jesus' preaching in this way (Mark 1:14-15; Matthew 4:17: and Luke 4:43). Matthew, Mark, and Luke are called the Synoptic Gospels because they have such similar wording and events that gospel experts unanimously believe they stand in some literary relationship to each other, meaning that they share common literary sources. The dominant theory for well over a hundred years is that Matthew and Luke both used Mark as a major source. Meanwhile, Christians since the 100s have recognized that something quite different is going on in John, with the second century Christian Clement of Alexandria calling it a "spiritual" gospel. It seems to give a less literal and more symbolic presentation of Jesus, as we will see in the second volume of this series.
 The Priene Inscription.