King or Lord

An interesting feature of the New Testament is that the gospels have many references to the kingdom of God, whereas Paul does not speak of the kingdom much at all. In Ephesians 1:10, Paul explains that God’s God's ultimate is,

to bring all things in heaven and on earth together under one head, even Christ.

This is the lordship of Jesus.

Jesus spoke of the Kingdom of God because he is humble. He was not going to go round preaching, “The Kingdom of Jesus” is coming. He could not preach that “I am the Lord”.

Paul did not face this constraint and wanted to honour Jesus. He understood that Jesus is the king of the Kingdom of God. By the time Paul was speaking and writing, Jesus had ascended into heaven and was seated at the right hand of God. By declaring that Jesus is Lord, Paul was acknowledging that the Kingdom of God is now the kingdom of Jesus.

Many Jews would have been happy if Jesus had become King of Judea, but Paul did not want any confusion about this issue. In Roman times, local kings like Agrippa and Herod were minor political hacks, whereas Caesar was Lord of the entire empire. When Paul described Jesus as Lord, he was putting him in a place far above these local kings, and far above Caesar.