This quote from The First Christmas by Marcus Borg and Dominic Crossan is rather long, but I liked what it said and felt like it would be difficult to distill it down to something shorter:

Eschatology is about the divine transformation of our earth. It is not about some mass immigration from a doomed world to a blessed heaven. Rather, it is about the end of this era of war and violence, injustice, and oppression. It is about the earth's transformation, not about its devastation. It is about a world of justice and peace.

How will this transformation of the world come about? To say the obvious, it has not yet happened, despite the passage of two thousand years. It is not yet accomplished. Does this mean that the Christmas stories are a pipe dream? That they (and the New Testament as a whole) are another example of failed eschatology, of hope become hopeless?

It depends upon how we think the new world is to come about. Two very different understandings, two different eschatologies, are found in the history of Christianity as well as in modern scholarship. We call the first one "supernatural eschatology," or "interventionist eschatology." Within this understanding, only God can bring about the new world. It can happen only through a dramatic divine intervention. All we can do is wait for it and pray for it. Many twentieth-century scholars argued that this is what Jesus and the earliest Christians expected. It has also been found in popular Christianity through the centuries. In our time, it is especially virulent in the violently destructive scenarios imagined by those who expect the second coming of Jesus in the near future.

We call the second one "participatory eschatology," or "collaborative eschatology." Put simply, we are to participate with God in bringing about the world promised by Christmas. Rather than waiting for God to do it, we are to collaborate with God.

There is a third option as well--namely, letting go of eschatology. This view is also found among Christians. Some do not see a connection between the gospel and a transformed earth. For them, Christianity is only about individual salvation, whether in this life or in a life beyond death. This world may be seen as a pleasant place or a dreadful place, but Christian hope is not about the transformation of the world.

We reject both the first option and the third option. We do not imagine that God will bring about a perfect world through divine intervention someday. We do not imagine a supernatural rescue of the earth. And we find the third option to be a betrayal of much of the Bible, both Old Testament and New Testament. The Christmas stories are not about a spectacular series of miraculous events that happened in the past that we are to believe in for the sake of going to heaven. Rather, they are about God's passion, God's dream, for a transformed earth.

We affirm the second option, participatory eschatology. Participatory eschatology involves a twofold affirmation: we are to do it with God, and we cannot do it without God. In St. Augustine's brilliant aphorism, God without us will not; we without God cannot. We who have seen the star and heard the angels sing are called to participate in the new birth and new world proclaimed by these stories. (pp. 240-242)