In terms of eschatology, it is so important to accurately portray an opposing position before engaging with it. So often, this is not the case and the result is a complete failure of any kind of productive dialog. As far as I understand the issues involved, I think Dr. Storms does a fine job of accurately representing the post-millennial view in this article below: (original source here)
“that view of the last things which holds that the Kingdom of God is now being extended in the world through the preaching of the Gospel and the saving work of the Holy Spirit in the hearts of individuals, that the world eventually is to be Christianized, and that the return of Christ is to occur at the close of a long period of righteousness and peace commonly called the ‘Millennium.’ . . . The Millennium to which the Postmillennialist looks forward is thus a golden age of spiritual prosperity during this present dispensation, that is, during the Church age, and is to be brought about through forces now active in the world. It is an indefinitely long period of time, perhaps much longer than a literal one thousand years. The changed character of individuals will be reflected in an uplifted social, economic, political and cultural life of mankind. . . . This does not mean that there ever will be a time on this earth when every person will be a Christian, or that all sin will be abolished. But it does mean that evil in all its many forms eventually will be reduced to negligible proportions, that Christian principles will be the rule, not the exception, and that Christ will return to a truly Christianized world” (The Millennium, 14; emphasis mine).
(1) According to postmillennialism, the Kingdom of God is primarily the rule or reign of God spiritually in and over the hearts of men. Thus the kingdom is truly present in this age and is visibly represented by the Church of Jesus Christ. In other words, the kingdom “arrives” and is “present” wherever and whenever people believe the gospel and commit themselves to the sovereignty of Jesus Christ as Lord.
(2) The kingdom is not to be thought of as arriving instantaneously or wholly by means of some cataclysmic event at the end of the age (an event such as the Second Coming of Christ). Indeed, the very name POST-millennialism indicates that Christ will return only after the kingdom has come in its fullness. The “arrival” of the kingdom, therefore, is gradual or by degrees. There may well be extended seasons in the life of the church where little visible and tangible progress is detected, indeed, even times when the church appears to regress in terms of its global influence. But postmillennialists are quick to remind us that we must take the long view and not succumb to the pessimism that easily grows in the soil of short-term setbacks. Whereas Satan’s kingdom may appear at times to experience a growth parallel to, if not greater than, that of Christ, the latter will most assuredly overcome all opposition in every sphere of life until the nations are brought into submission to him.
(3) The means by which the kingdom extends itself is the gospel of Jesus Christ. The continuing spread and influence of the gospel will increasingly, and in direct proportion thereto, introduce the kingdom. This gradual (but constantly growing) success of the gospel will be brought about by the power of the Holy Spirit working through the Church. Eventually the greater part, but not necessarily all, of the world’s population will be converted to Christ. As Greg Bahnsen explains, “the essential distinctive of postmillennialism is its scripturally derived, sure expectation of gospel prosperity for the church during the present age” (“The Prima Facie Acceptability of Postmillennialism,” in The Journal of Christian Reconstruction, III, Winter 1976-77, 66).
As Doug Wilson explains: “the gospel will continue to grow and flourish throughout the world, more and more individuals will be converted, the nations will stream to Christ, and the Great Commission will finally be successfully completed. The earth will be as full of the knowledge of the Lord as the waters cover the sea. When that happens, generation after generation will love and serve the Lord faithfully. And then the end will come” (Heaven Misplaced, 10).
(4) At what point, then, does the “millennium” begin? Postmillennialists differ in their response to this question. Some say the millennium covers the entire inter-advent age (i.e., the whole period of time between Christ’s first and second comings), whereas others conceive of the present age as in some sense blending or merging into the millennium. In other words, some postmillennialists see the millennial kingdom as present throughout the whole of the current age whereas others reserve the word millennium for the latter day, publicly discernible, prosperity of the Christian Church.
(5) This ever-increasing success of the gospel will bring in its wake a reduction (although not a total elimination) of the influence and presence of sin. Righteousness, peace, and prosperity will flourish. Thus, writes Bahnsen, “over the long range the world will experience a period of extraordinary righteousness and prosperity as the church triumphs in the preaching of the gospel and discipling the nations through the supernatural agency of the Holy Spirit” (63). Postmillennialism “does not teach that every individual who has ever lived on earth will be saved, nor does it teach that there will be a time prior to the Second Coming when every living individual will be converted. But it does believe that there is sufficient scriptural warrant to say that at some point in history there will be worldwide conversion on an unprecedented scale” (Keith Mathison, Postmillennialism, 193-94).
(6) The gospel will also sustain a positive influence in every sphere of society: the economic, political, and cultural life of mankind will be vastly improved. The Church will witness nothing less than “the worldwide dominion of Christ and his elect, the re-establishment of Christian civilization and Christian culture” (Sandlin, A Postmillennial Primer, 32). Therefore, this triumph or victory of the Church in the present age is not simply the spiritual or invisible victories in the Christian’s heart or the internal blessings privately experienced by the Church. The prosperity will be visibly and publicly acknowledged. Every domain of human activity will be renewed according to Christian principles and thus brought into service for the glory of Jesus Christ. It is this progressive subjugation of Christ’s enemies and ever-expansive influence of his sovereign lordship, throughout the course of the present age, that Paul has in view when he says in 1 Corinthians 15:25, “For he must reign until he has put all his enemies under his feet.” Thus, as several postmillennialists have been heard to say, “Christ will return to a truly Christianized world.”
(7) At the end of the present age, that is, after the kingdom has spread visibly and powerfully throughout the world but just before Christ returns, there will be a brief time of increased Satanic activity and apostasy (see Rev. 20:7-10). This final rebellion will be crushed by the glorious return of Jesus Christ to the earth, at which time there will immediately follow the general resurrection, final judgment, and eternal state. “In short, postmillennialism is set apart from the other two schools of thought [premillennialism and amillennialism] by its essential optimism for the kingdom in the present age” (Bahnsen, 66). It should also be mentioned that many postmillennialists believe as do most premillennialists that a mass conversion will occur among ethnic Israelites. Of course, unlike the dispensational premillennialist the postmillennialist denies that this salvation of physical Israel has for its purpose a restoration of the nation in a future earthly millennium.
(8) The central distinguishing feature of postmillennialism which sets it apart from both amillennialism and postmillennialism is its belief in the success of the great commission in the present age. Simply put, the nations will be baptized and discipled to the glory of God. The best summation of postmillennial eschatology is provided by Greg Bahnsen:
“The optimistic confidence that the world nations will become disciples of Christ, that the church will grow to fill the earth, and that Christianity will become the dominant principle rather than the exception to the rule distinguishes postmillennialism from the other viewpoints. All and only postmillennialists believe this, and only the refutation of that confidence can undermine this school of eschatological interpretation. In the final analysis, what is characteristic of postmillennialism is not a uniform answer to any one particular exegetical question . . ., but rather a commitment to the gospel as the power of God which, in the agency of the Holy Spirit, shall convert the vast majority of the world to Christ and bring widespread obedience to His kingdom rule. This confidence will, from person to person, be biblically supported in various ways . . . . The postmillennialist is in this day marked out by his belief that the commission and resources are with the kingdom of Christ to accomplish the discipling of the nations to Jesus Christ prior to His second advent; whatever historical decline is seen in the missionary enterprise of the church and its task of edifying or sanctifying the nations in the word of truth must be attributed, not to anything inherent in the present course of human history, but to the unfaithfulness of the church” (68).
(9) The postmillennialist points to several texts that he/she believes supports this view, included among which are: Psalms 2:6-9; 22:27-28; 72:8-11; 86: 9-10; 102:15; 138:4-5; Isaiah 2:1-4; 9:6-7; 11:6-10; 65:17-25; 66:18-23; Daniel 2:31-35; 7:13-14; Zechariah 9:9-10; Matthew 13:31-33; 1 Corinthians 15:20-26.
(10) Among the many misconceptions about postmillennialism, I briefly mention the following. First, postmillennialism has been mistakenly linked and often identified with belief in the inherent goodness of man. This has occurred despite the fact that the vast majority of postmillennialists today (and perhaps even in the past) are Calvinists. The result is that postmillennialists have been unjustifiably charged with failing to take seriously the biblical pessimism regarding humanity’s efforts apart from the sustaining power of divine grace and, as a result, have been accused of saying that the kingdom of God would be ushered in by human effort alone, independently of the Holy Spirit.
Second, is the fact that postmillennialism has been mistakenly identified with the notion of evolutionary optimism and other secular notions of historical progress. But the kingdom of God in evangelical postmillennialism is not the product of natural laws of improvement in an ever-upward evolutionary progression, but rather the fruit of the supernatural energy and operation of the Holy Spirit, primarily through the proclamation of the gospel of Jesus Christ.
Third, postmillennialism has been mistakenly identified with theological liberalism and the so-called “social gospel”. Thus the kingdom it espoused came to be perceived as some sort of secular utopia that replaced the return of Jesus as the true hope of the church.
Fourth, there is the false charge that postmillennialism teaches salvific universalism. Whereas postmillennialists do indeed look forward to a day in which vast numbers shall turn to faith in Jesus Christ, at no time do they expect that all will be converted or that sin will be entirely eliminated prior to the eternal state. Evangelical postmillennialists believe no less fervently than premillennialists and amillennialists in the doctrine of hell and the irreversible damnation of those who die without Christ.
Fifth, postmillennialists have been accused of being naïve and unrealistic. Appeal is often made to extra-biblical events and historically catastrophic occurrences such as World War I, World War II, the nuclear arms buildup, and the ever-disintegrating moral fabric of Western society, and in our day, especially, the rise of radical Islam and international terrorism. To the minds of many, such facts discredit postmillennialism and confirm the more pessimistic philosophy of history espoused by premillennialism. A number of postmillennialists have labeled this approach to prophecy (and rightly so) as “newspaper exegesis” in which current events (i.e., the Wall Street Journal, Fox News, and USA Today) are studied to determine the future rather than the Bible itself. Needless to say, the decisive factor is not discernible trends in our world or the condition of mankind in general but rather whether or not the Bible, God’s inspired Word, foresees the worldwide triumph of the gospel.
Sixth, and finally, postmillennialists have been mistakenly represented as believing that once the tide turns for good, so to speak, all that remains is a progressive increase of righteousness and peace and the utter absence of evil in the world. But all evangelical postmillennialists believe that there yet remains one final outbreak of evil of undetermined length preceding the second coming of Christ. Satan will be released from the restrictions placed upon him (Rev. 20:1-3) and will foment a global rebellion against Christ and his Church (Rev. 20:7-10). There will likely be a final attempt to persecute and oppress the church on the part of those who participate in this last-gasp effort of the Enemy, but it will be to no avail. Christ will prevail.