Three Views of the Millennium
Revelation 20 speaks of a thousand years in which Satan is bound and Christ reigns. This passage, among other biblical texts, has created debate as to how to interpret this millennium. There are three major views of the millennium and what it means for the church. The first view is amillennialism, which teaches that the church age is this millennium. Amillennialists take the reference of a thousand years to be symbolic, meaning a long period in which the church is the visible representation of the kingdom of God on earth. Amillennialists often hold to a pessimistic view of history in which the world will become increasingly wicked, leading to the return of Christ to the earth. Immediately after Christ returns, He judges the world and creates the new heavens and the new earth.
Premillennialism, in contrast, argues the church age is not the millennium, but rather there will be a seven-year tribulation such as the world has never seen before, after which Christ will return and set up His kingdom on the earth, ruling from the throne of David. In particular, according to premillennialism, the millennium will begin upon Christ's return and victory over the army of the Antichrist. This millennium is a literal thousand years in which the promises made to Israel in the Old Testament will be fulfilled, and it will be a time of unprecedented prosperity with Christ as the ruler over the entire world. Premillennialism is also a pessimistic view of history because it argues that the world will degrade and will get worse and worse until the tribulation and subsequent return of Christ, after which Christ sets up His kingdom on the earth for a thousand years.
Postmillennialism stands in contrast to both amillennialism and premillennialism because it is an optimistic view. Postmillennial theology argues the world will get better and better until Christ comes back. Postmillennialists often argue the church age leads to the millennium and Christ comes back at the end of the millennium, which is why it's called postmillennialism. The church influences the world for good to the extent that at some point in the future, the majority of people will be saved on earth. This inaugurates a period of great prosperity and blessing and postmillennialists would also see the reference to the thousand years as being symbolic of a long period, not necessarily a literal thousand years.
On the surface, this can seem to be a very appealing view of the church and the world. After all, Jesus gave the command to the church to go into all the world and make disciples right before He was taken back into heaven. Postmillennialism argues that we will succeed in that endeavor and bring about the millennium after which Christ will come back. Postmillennialism emphasizes the influence that the church has upon the world. Postmillennialists sometimes disagree on how this change in the world will happen. For example, some would argue that Christians should seek to change the government or even the education system to spread the influence of Christianity. Whatever the means, postmillennialists will take a positive view of the future. There have been many Christians throughout church history who have adhered to postmillennial theology, including many of the Puritans. Postmillennial theology is also growing in the church today, with many Christians opting for an optimistic view of the future influence and growth of the church.
The biblical texts dealing with the millennium are certainly debated. Matthew 24 is a key passage that speaks of Christ's return. In this passage, Jesus is explaining to His disciples the signs that will come before He comes back. These signs include many wars, famines, earthquakes, intense persecution of the church, and great tribulation, such as has not occurred since the beginning of the world until now, nor ever will. Matthew 24:29-31 says, "But immediately after the tribulation of those days, the sun will be darkened, the moon will not give its light, and the stars will fall from the sky, and the powers of the heavens will be shaken. And then the sign of the Son of Man will appear in the sky, and then all the tribes of the earth will mourn. They will see the Son of Man coming on the clouds of the sky with power and great glory, and He will send forth His angels with a great trumpet, and they will gather together His elect from the four winds, from one end of the sky to the other." Postmillennials often take passages like Matthew 24 as already having been fulfilled in the past, most notably in the destruction of Jerusalem by Titus in AD 70. This is because the description seen in Matthew 24 doesn't have a great place in postmillennial theology, since the world is supposed to get better and better, not fall into chaos before the coming of Christ.
Good scholars disagree over these passages, but I would hold that a natural reading of the text points to the decline of the world and the persecution of the church, not to the church's victory. Victory will be realized when Christ returns and sets everything right as the King of Kings and Lord of Lords.