One recurring objection to postmillennialism is that at base this eschatological system is liberal, reflecting liberalism’s historical outlook. This is largely charged because of postmillennialism’s confidence in the glorious future progress of human civilization. Oftentimes anti-postmillennialists draw parallels between the optimistic expectations of postmillennialism and those of the social gospel. For instance, amillennialist Kim Riddlebarger suggests a linkage between postmillennialism and liberalism, even though he denounces the dispensational tendency to link amillennialism with liberalism.  Dispensationalist John Walvoord complains that postmillennialism cannot resist the tendency to liberalism in that it “lends itself to liberalism with onl minor
But this rebuke of postmillennialism is absurd on at least three grounds.
First, certainly older forms of social liberalism were optimistic regarding mankind’s future. But equating theological liberalism with historical optimism is surely fallacious. Is optimism a fundamental, descriptive attribute of liberalism, so that to affirm it one must be liberal? This does not make good sense.
Second, what are we to make of Walvoord’s statement that postmillennialism cannot resist the tendency to liberalism in that it “lends itself to liberalism with only minor adjustments”?
This is an incredible and indefensible assertion. Postmillennialists believe that it is the Holy Spirit empowered gospel of the resurrected Son of God that will transform the hearts and lives of men, thereby dramatically affecting the progress of human history. We also believe in the visible, glorious return of Christ, the physical resurrection of the dead, and the Great Judgment of all men assigning some to heaven and others to hell. Are these elements of postmillennialism simply “minor adjustments” to the wholesale humanism of the social liberalism?
Walvoord’s remarkable assertion overlooks the fundamental supernaturalism inherent within postmillennialism and suggests that the wholesale naturalism involved in liberalism are only minor differences! As Iain Murray observes: “the naturalistic optimism of the nineteenth century stood opposed to the old theology all along the line.”
Third, the objection is even wrong by definition. Postmillennialism by definition cannot be liberal: the term “postmillennial” means that Christ will return post the millennium. Hence, its eschatology is “post” + “millennial.” What liberal believers that Christ will return at all? Liberals, such as Rudolf Bultmann, hold that Jesus’ bones are rotting somewhere in a tomb in Israel.
Thankfully, amillennialist Robert Strimple has accepted my argument that postmillennialism by definition cannot be equated with liberalism: “I express appreciation for Pastor Gentry’s attempt to establish his postmillennial eschatology on a biblical basis. Surely he has laid to rest the charge (too often heard in the past) that the kind of evangelical postmillennialism he advocates rests on liberal, humanist, evolutionist presuppositions.” 
So then, postmillennialism is not — and indeed, cannot — be liberal. Christians may not like the prospect of a happy and glorious future resulting from Holy Spirit empowered gospel preaching, but they cannot reject it on the charge that it is liberal!
1. Kim Riddlebarger, A Case for Amillennialism: Understanding the End Times (Grand Rapids: Baker, 2003), 30, 35.
2. John F. Walvoord, The Millennial Kingdom (Findlay, Ohio: Dunham, 1959), 35; also 34.
3. Murray, The Puritan Hope, 210.
4. Robert Strimple in Darrell L. Bock, ed. Three Views on the Millennium and Beyond (Grand Rapids: Zondervan, 1999), 58.