Postmillennialism is another fascinating part of the story told by Daniel Walker Howe in What God Hath Wrought: The Transformation of America, 1815-1848. Many Christians today who buy into the narrative of “American Exceptionalism” cite Christian and Biblical influences on the U.S. Constitution as a key reason for America’s success — in particular, the Calvinist-inflected idea that checks and balances are necessary to limit the sinful tendencies of government officials. But very few would embrace a much more important driver of the link between religion and the early belief in American exceptionalism: postmillennial eschatology.
In brief, postmillennialism is the belief that the evangelistic and reform efforts of the Church will result in the conversion of substantially the entire world and will produce the peaceful and prosperous thousand-year reign of Christ alluded to in Revelation 20:4-6. I think it’s fair to say that most serious, trained Christian theologians today are Amillennial — that is, they understand this text to be metaphorical and symbolic, not a reference to a “literal millennium” (this is my view). It’s also fair to say that, in terms of historical theology, the most widely held position throughout Church history has been “premillennialism” — the belief that temporal judgment will occur before a literal millennium.
Particularly in North American evangelical Christianity, of course, many if not most believers at the popular level are “premillennial,” with a “dispensationalist” flavoring — that is, they think a literal millennial reign will occur after Christ first judges the world with terrible destruction (the “Great Tribulation”) and removes Christians from the earth (the “Rapture of the Church”). Premillennialist Christians disagree on the timing of the “Rapture,” but the most popular version asserts that it will occur before the Tribulation (this is the view underlying the “Left Behind” franchise of books and movies). The belief in a “Rapture” is not a significant part of historic premillennialism.
Most American protestant Christians in the Nineteenth Century, however, including nearly all evangelicals, were postmillennial. They believed that their efforts were spurring on a golden age to be capped by Christ’s return. As Howe notes, for example, revivalist Charles Finney once “told his congregation that if evangelicals applied themselves fully to the works of mission and reform they could bring about the millennium within three years.” “Postmillennialism,” Howe suggests, “provided the capstone to an intellectual structure integrating political liberalism and economic development with Protestant Christianity.”
The sort of evangelical Christianity that is now emerging among many educated North American Christians has taken on some of this dynamic. Although this small but growing segment of American evangelicalism largely rejects dispensational premillennialism in favor of amillennialism, it (we) are emphasizing the this-worldly aspects of the Gospel — the ways in which the already-present “Kingdom of God” is concerned with freedom from oppression and material relief for the poor. Missional theology, for example, incorporate the dynamic of postmillennialism without the Biblicism of a literal millennium. On the whole, I think this is a positive development, particularly in that it properly separates the Kingdom of God from any earthly polis. And the need for this sort of separation ultimately renders talk of any sort of National Exceptionalism idolatrous.