According to postmillennialism, the gospel will continue to advance with great success, and most of the world’s population will be regenerate by the end of the present age. As postmillennialist Loraine Boettner explains:
Postmillennialism is 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.
In a similar way, postmillennialist Kenneth Gentry writes:
Postmillennialism expects the proclaiming of the Spirit-blessed gospel of Jesus Christ to win the vast majority of human beings to salvation in the present age. 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 people and of nations. After an extensive era of such conditions the Lord will return visibly, bodily, and in great glory, ending history with the general resurrection and the great judgment of all humankind.
So my question is this: Since postmillennialists view the thousand-year millennial kingdom of Revelation 20 as coming to an end at the conclusion of the present age—to then be followed by the second coming of Christ—how do they explain the rebellion in Revelation 20:7-9?
When the thousand years are completed, Satan will be released from his prison, and will come out to deceive the nations which are in the four corners of the earth, Gog and Magog, to gather them together for the war; the number of them is like the sand of the seashore. And they came up on the broad plain of the earth and surrounded the camp of the saints and the beloved city, and fire came down from heaven and devoured them (Rev 20:7-9).
Do you see the problem? If postmillennialists believe that the world will be “Christianized” in such a way that “a vast majority of human beings” will be saved by the end of the thousand years, how do they account for this massive rebellion prior to the return of Christ? How is it possible that a mass of unbelievers numbering like the sand of the seashore could arise in a world that is almost entirely regenerate?