Why ‘New Jerusalem’?
We are aliens and strangers in a world that is not our home.
Abraham made his home in the promised land like a stranger in a foreign country. Called by the God of glory to leave all behind and go wherever He lead, he had no choice but to believe in the promises: promises of land, of a son, and of blessing that would spread to every nation.
This was his righteousness: not that he had anything in himself, but that he was a recipient of an ‘alien righteousness‘; the gift of a God of lavish grace. Abraham now stands as the example of anyone who would be in a right relationship with God: simply trust; agree that God is the just judge who will do what is right; know that He alone is our sovereign and reward.
We see that God has ‘done right’ in the crucified, risen Son. This is what is meant by Paul in Romans when he explains that the Gospel of Jesus Christ both reveals the righteousness of God, and enables all who believe to be a recipient of that righteousness: to be justified.
He may not have been able to articulate it in the way we do, but Abraham trusted in Christ. The same Christ who is trusted by billions today.
Like Abraham, Christians are called to leave the emptiness of the world and idolatry and go to the land that God will show us: a new heavens and a new earth, where righteousness makes its home.
The centrepiece of this new creation is a city: the New Jerusalem. Not a physical or literal city, the New Jerusalem is and will be the People of God, in whom the triune God dwells. There is no temple in this city, because the city is the temple. We will not have to travel to find the presence of God, for we will see Him face to face.
This is our true home: Not a place but a person. Authentic living is to know the true God, and Jesus Christ whom he has sent.
Until that day we travel as sojourners and strangers in a foreign land. We may pitch our tents from time to time, but there is no place for bricks and mortar. Our mission is not to fix the world, but to call the world to repentance.
The resource we have is the full power of God in the Gospel. This Gospel – the world shaking news that the crucified and risen Messiah Jesus is the King of God’s kingdom – enables us to live lives full of grace and peace, to speak words seasoned with salt, to be a prophetic voice to the world in which we currently reside, and to do all things to the glory of God:
Sola scriptura
Sola fide
Sola gratia
Solus Christus
Soli Deo gloria
New Jerusalem 
James, I am not sure this gives the most accurate picture, or summary, of our life in this world. From one point of view, we have no other world, than this one. And we never will. It is just that it will be redeemed. The ‘false world’ and its false systems, will be brought to an end. Btw, I think you meant to write “our mission is not to fix the world but to call the world to repentance”. Surely, though, a change of mind includes an authentic approach to participation in this world; that would mean fixing some of the things that are within our capacity to do so… Trevor.
Trevor, thanks for your feedback. When I use the word ‘world’ here I mean the fallen human system that stands in sophisticated rebellion against God, rather than the physical creation in which we live. So we are not of this world; this world hates us as it did Jesus; and this world will one day come to an end when its kingdom has become the kingdom of our God and of His Christ.
Typo fixed!
James
Yes – I agree.
Since there have been many Christian theological systems that have conflates “world system” with “planet earth” and “the creation” , the. I reckon many would probably be hearing your meaning …as otherwise.