The Covenantal Kingdom
The Biblical and Theological Issues
Debates on eschatology tend to be confusing. There is, of course, a vast amount of Scripture to be dealt with, and the passages to be interpreted are admittedly sometimes complex. Add to this a long history of theological debate, and it is easy to see why the subject of eschatology can be bewildering. But it doesn't have to be this way, as we shall see.
Defining the Issues
There are three basic positions regarding the time of the second coming of Christ. Premillennialism teaches that Christ returns before the end of history to inaugurate an earthly kingdom of a thousand years. Amillennialism denies an earthly kingdom age and says the coming of Christ is the end of history. Postmillennialism agrees with amillennialism that the coming of Christ ends history. It also agrees with premillennialism that there will be a kingdom of God on earth and in time. However, the postmillennialist believes that Christ will bring in His kingdom through the work of the Holy Spirit in the Church and then return to this world at the end of the history when God's kingdom purposes have been fully realized.
Two Theological Questions
Greg Bahnsen  has narrowed the eschatological debate to two specific theological questions:
To this question the premillennialist answers no. For the premillennialist the church age is distinct from the future millennium. Christ returns at the end of the church age to inaugurate the millennium. The final resurrection and judgment occur a thousand years later.
Both the amillennialist and postmillennialist answer yes. Though for different reasons, these positions agree that the Bible teaches that the final judgment, resurrection, and return of Christ synchronize with each other. The millennium for the amillennialist occurs in heaven during the church age. For the postmillennialist the millennium is the final era of the church age.
To this question both the premillennialist and amillennialist answer no. They agree that the Gospel will never be victorious in history. The postmillennialist answers yes. He believes that the command of Christ guarantees the victory of the Gospel.
If the postmillennialist can demonstrate that, according to the Bible, the coming of Christ is at the end of history (including the end-time events of the resurrection and judgment), he will have proved his position against the premillennialist. If he can demonstrate that the Gospel of Christ will be victorious within history, resulting in the conversion of the majority of the human race and leading to an age of unparalleled blessing, he will have proved the correctness of his position in contrast to the amillennialist. 
The eschatological debate, therefore, is less complicated than it may seem at first. Just two straightforward questions: 1) Does Christ return at the end of history? 2) Will the Holy Spirit succeed in converting the majority of the human race by the Gospel? Answer these questions Biblically, and eschatology is saved from the rhetorical fog of endless theological disputation. The postmillennialist believes that the Biblical answers to these two simple but theologically decisive questions demonstrate the truth of the postmillennial position.
 Greg Bahnsen, "The Prima Facie Acceptability of Postmillennialism" in The Journal of Christian Reconstruction, Winter 1976-77, vol. 3, no. 2, pp. 64ff..
 Ibid., p. 65.
 Of course, the premillennial position would also be refuted by Scriptural evidence of the global success of the Gospel. As Bahnsen also points out, these two points can be further reduced to the single issue of the success of the Gospel. Ibid., p. 68.