The Kingdom of God and the Already - Not-Yet Tension

In thinking about the Kingdom of God, there is an apparent and necessary tension between the Kingdom having come with the incarnation of Jesus Christ, and the Kingdom to come when He returns.  Below is a series of verses that show the tension.  Afterwards is a very brief discussion of why this tension must be maintained.

The Kingdom has already come:
Luke 17:20-21: “Once, on being asked by the Pharisees when the kingdom of God would come, Jesus replied, ‘The coming of the kingdom of God is not something that can be observed, nor will people say, “Here it is,” or “There it is,” because the kingdom of God is in your midst.’”
So, when Jesus came to the earth, it was right for Him to tell others wherever He is, the Kingdom of God is.

The Kingdom is yet to come:
Luke 21:25-31: “There will be signs in the sun, moon and stars.  On the earth, nations will be in anguish and perplexity...Even so, when you see these things happening, you know that the kingdom of God is near.”
However, until Jesus returns a second time, the kingdom of God has not yet come in its fullness.  Thus, it is right for Jesus to say that even as the signs of the end times begin to unfold, the Kingdom of God has not yet come,  but is near.


Why does it matter?
For those who only think the Kingdom has already come, they have an over-realized view of the end times (eschatology).  This can negatively affect their views several ways.  One is that they deny the ongoing existence and struggle with sin.  An over-realized eschatology can be accompanied with an over-realized personal sanctification.  The end result is an emphasis on grace that denies or at least downplays personal responsibility.  A person uses the Kingdom’s presence, and Christ’s atonement to downplay or deny their own sin struggles.  In the end, an over-realized eschatology can produce someone who claims to be a Christian, but does not continue the struggle against sin and the necessary work to become more like Christ through the power of the indwelling Holy Spirit.  

For those who only think the Kingdom is yet to come, they have an under-realized eschatology.  They have not grasped that at Jesus’ first coming, the Kingdom of God began breaking into this world, that the power of sin and death was defeated on the cross.  Jesus has dealt Satan the crucial blow, and the beast’s power diminishes.  An under-realized eschatology over-emphasizes the power of sin and death to the point that the power to really change is denied.  This diminished view of sanctification can be used to justify perpetually ongoing sin struggles.  In the end, like the first view, an under-realized eschatology that denies the power of the Holy Spirit to indwell and change the believer now (not only when Christ returns) can be used as an excuse for a life of disobedience.

The solution is to hold both beliefs in tension.  When Christ came to earth as a baby in manger, God with us, He lived a perfect life, and then took on Himself the punishment we deserved (Rom 5:8, 1 Pet 3:18).  By doing so, the perfect man conquered sin (He was sinless) and death (as the sinless man death had no hold on him), see 1 Cor 15:20-23, 55-57, Rom 6:23.  Thus, the Kingdom, or perhaps equally understood as the Kingship of God, has come because the King came.  But, as long as sin and death exist, the Kingdom of God has not fully come.  As Paul says, “the end will come, when he [Jesus] hands over the kingdom to God the Father after he has destroyed all dominion, authority and power. For he must reign until he has put all enemies under his feet.  The last enemy to be destroyed is death,” (1 Cor 15:24-26).  He is reigning, but His reign is not yet complete because the enemies have not been fully destroyed.  Thus, we live between the inauguration of Christ’s reign and the fulfillment of Christ’s reign.  Sin and Satan and death have been defeated at the cross but not entirely destroyed.  Through Christ we are graciously forgiven of our sin and freed from its dominion, but we are not fully immune to its lure and must fight by the power of the Spirit to put sin to death as Paul said, “If you live according to the flesh, you will die; but if by the Spirit you put to death the misdeeds of the body, you will live,” (Rom 8:13).  We are made alive in Christ, and now we must live the abundant life through the power of His indwelling Spirit, persevering until He calls us home or returns in power.

Resources: 
George E. Ladd has written a helpful book summarizing this topic well called, “Gospel of the Kingdom: Scriptural Studies in the Kingdom of God.” (http://amazon.com/dp/0802812805).