Calvin Codger is a pseudonym. I am 1689 LBC Reformed Baptist. I live in the Southeastern United States.

Postmillennials assert that the kingdom is both a heavenly and an earthly reality, one that is both seen and unseen, one that is born from heaven yet is expanding in this world to be fully consummated when Christ returns. Postmillennials would look for God’s kingdom to come and will to be done on earth as in heaven, and would expect that these triumphs would be gradually realized until the time of Christ’s return. The postmillennial position anticipates the gospel to advance in tangible ways in this world, as the outworking of God redeeming men and women will progressively lead to redeemed culture, peoples, and world itself. Timing is not a concern for this task, as this progressive triumph will have a sort of ebb and flow (ups and downs), and its consummation may yet be far off in the future (though it need not be of necessity). This kingdom triumph is also wholly a work of God—the kingdom does not expand by virtue of human effort, yet the kingdom’s advance certainly includes both heaven and earth in its wake.

― Josh Howard, Eschatology Matters

The kingdom is often limited to the hearts of the regenerate, heaven, or the eternal state. This virtually denies that the messianic kingdom has anything to do with this present earth. In contrast to this tendency, Scripture makes it abundantly clear that this earth, although not the source of the kingdom, is a part of the kingdom. Christ’s messianic authority and reign extend over all of heaven and earth (Matt. 28:18), and He is in the process of subduing all of His enemies, whether in heaven or on earth (1 Cor. 15:25).

― Keith A. Mathison, Postmillennialism: An Eschatology of Hope

Postmillennialism holds that the Lord Jesus Christ established his kingdom on earth through the preaching and redemptive work in the first century and that he equips his Church with the gospel, empowers her by the Spirit, and charges her with the Great Commission to disciple all nations. Postmillennialism expects that eventually the vast majority of men living will be saved. Increasing gospel success will gradually produce a time in history prior to Christ’s return in which faith, righteousness, peace, and prosperity will prevail in the affairs of men and nations. After an extensive era of such conditions the Lord will return visibly, bodily, and gloriously, to end history with the general resurrection and the final judgment after which the eternal order follows

― Kenneth Gentry, He Shall Have Dominion

I also agree with the postmils that in the long run this age can be seen as an age of Christian triumph, not only in narrowly “spiritual” matters, but in the church’s social influence as well. That is in fact what we see in history: believers are always persecuted in some measure; but eventually Christianity triumphs and comes to profoundly influence the institutions of the societies it touches. 

John Frame