Postmillennialists who believe the world will be Christianized prior to the return of Christ criticize both Pre- and A-millennialism as being 'pessimistic' in their outlook.
By this they mean that since we believe that the world is not going to get better, then we are by default anti-optimistic and defeatist in how we view the Church in this age.
They on the other hand believe the Golden Age is yet future and that eventually the entirety of the Earth will be converted to Christianity. Some even believe this Earthly victory will be accompanied by great advances in science and technology which will lead to longer life and at least in part a reversal of the effects of The Fall.
This theology was fairly dominant up until the World Wars. An older school of thought known as Historicism had been combined with a general expectation of Christ's Victory through the Church 'in time'.
Most viewed this victory in terms of the Kingdom of God being equated with Western Civilization or Christendom.
Modernist Theology took this same 'optimistic' impulse and transformed the same basic idea into the Social Gospel which was merely a partially secularised version of the same overall vision. There was a greater emphasis on society and culture and less on the particulars of the atonement and what we would call the basic Gospel message.
By the early 20th century the Belle Époque had come to a cataclysmic end. Of course it wasn't a beautiful age to those at the lower end of society or for much of the world which had been colonized by Western powers.
One can see how if Christendom or the West were viewed as virtually identical to the Kingdom of God why they would be so optimistic. By the early 20th century the West had all but conquered the Earth. Then in a moment of tragic irony the Western Powers turned their guns on one another and brought it all down over the next thirty years.
The new teaching of Dispensationalism was afoot and rapidly expanding its influence. In an age of Theological Modernism it seemed like the new Bible Conference teachers were the really serious students of the Bible. In contrast with Confessional traditions they seemed like a breath of fresh air and a return to a no nonsense tradition-absent reading of Scripture.
And, with all the tumult in the world, the fall of dynasties and the terrors of Communism and Fascism on the rise, the era did indeed have an apocalyptic flavour.
The publication of the Scofield Bible did much to help the Dispensational cause. A combined interest on the part of older Postmillennial readings of Romans 11 and the new Dispensational theology with its emphasis on the Jewish nation restored in Israel with a rebuilt Temple (and all the rest) helped encourage the British to issue the Balfour Declaration, the Zionist seed of the modern state of Israel which was violently ratified by the survivors of the Holocaust.
Postmillennialism waned. Some maintained the older form which has today been called Pietistic Postmillennialism by some. This was the old Revivalist tradition that thought world Christianization would come about through massive revivalistic outpourings of the Holy Spirit. There would be mass conversions and how that affected society... that wasn't really the concern.
In the 1960's some American Calvinists were becoming very concerned. The loosely 'Christian' social consensus was in a state of collapse. Instead of moving closer to the Golden Age, every day seemed to move society in the direction of Secularism and a rejection of Christianity. What to do? How would the Golden Age come about?
They argued that instead of looking for 'Revivals' the answer was to work on the intellectual foundations of society. Some believed the West could be rescued if the Church got busy. Others thought it was too late and the best thing to do was to prepare, grow the Church (especially through the venue of the family) and prepare so that readied and educated descendants could step into the civilizational gap when everything collapsed. They played a key part in the early home school movement.
The hard-line faction developed into the Theonomic movement which quietly grew in the 1970's and really came into its own during the period of Christian political ascendancy in the 1980's. The cultural firestorm of the 1990's shined the spotlight on the movement, helped it grow, but also generated a great deal of controversy and criticism.
Their more or less insistence on a literal application of Mosaic case law and punishments to modern American society seemed extreme if not absurd to many but it generated a debate about the questions of what 'standard' was to be used in the governing of society.
Two of the main players, Greg Bahnsen and RJ Rushdoony died in 1995 and 2001 respectively, and since then the movement has dissipated... but the ideas live on even if in somewhat modified form.
I have several file folders filled with papers from the 1990's ...Chalcedon, SCCCS, Still Waters Revival Books and many more. It's interesting to revisit those papers and that time. I was a new Christian and at that point was both intrigued and challenged by their views. I knew they were wrong and whenever I had any doubts I merely had to start reading my Bible. Though I did not yet possess the knowledge to properly interact with them or defeat their arguments it was patent to me from a simple reading of the New Testament that they had gravely misread and misunderstood the nature of the New Testament Christianity. Only later did I learn how correct I had been.
They always insisted they were 'Whole-Bible Christians', and while that sounds impressive and God honouring it is neither true nor framed in accord with what we learn in the New Testament. We are certainly followers of Scripture in its entirety, and it is certainly the same Almighty God who authored both, but the New Testament helps us to understand the Christocentric nature of the entire Bible. Theonomy misses this in its emphasis on the Old Testament and its focus on the laws which served as types and symbols of Judgment and the penalty for sin... a typology that was fulfilled at the Cross.
This theme regarding the Gates of Hell is a constant in their literature. The Gates of Hell will not prevail against the Church. The language they insist is offensive in nature, as in, the Church will assault and kick down the gates. Gates they insist are defensive thus demonstrating the Church's posture is to be on the offensive, positive and victorious in its mindset. We attack the Gates of Hell and by this they mean we take over the world and transform it. A failure to grasp this means the Church will be pessimistic in its posture, defeatist and impotent.
At the time I was a new Christian and I remember this creating a bit of a conundrum for me. I already knew they were mistaken but there were a few passages like this that I didn't really know how to respond to.
Later I learned that marking out or 'measuring' is a symbolic action in the prophetic writings. We see this clearly in Jeremiah 31 and certainly in the last eight chapters of Ezekiel. We even see it in Revelation 11.
God marks out His territory, delineating and separating the holy and covenantal from what is not, from what is the world. Again this declaration is symbolic using the land or a geographic space to mark out the holy city from the spiritual Gentile world. And of course the 'space' that is being marked out is in reality the body of Christ. The typology never had anything to do with a temple or land. Those were symbols fulfilled by Christ. This is marking out His people Israel, the holy and redeemed from the world.
The imagery of walls and gates isn't so much a visualization of a battle tactic as much as it is a way of marking out and separating.
How would the Gates of Hell prevail?
It's interesting because the idea conveyed by the word translated as prevail implies offense, as in the Gates of Hell are marching toward us but will not prevail.
How do Gates advance? They don't. The Postmillennialists are right in this sense. They're defensive.
But the language does suggest the Gates are on the offense seeking victory. The Gates are not the physical objects or even the image of the physical objects. It's symbolic for the kingdom of Satan.
I'm afraid they're over-reading the imagery. They're guilty of hyper-literalism.
The picture or in reality the idea would have been familiar to the Apostles. They would have thought of Ezekiel and the measuring out of the Temple etc...
The Gates have to do with marking out or claiming. That's how they would advance or prevail. Christ's declaration simply means that Hell will not be able to encircle the Church and 'claim' it within its gates.
The kingdom of Hell will not defeat the Church.
That said, if you did want to insist on reading it the other way, even then the Postmillennial vision would not be vindicated. At that point we would understand the imagery in terms of the final victory secured by Christ. He will indeed 'smash the gates' at His coming. The demonic kingdom will be utterly vanquished. It will not stand. It will not prevail. But I think the first reading is how it should be properly understood.
All of this said, this does not mean they we are to be pessimistic. Far from it. We are filled with a blessed hope, a hope that does not rest in This Age but in The Age To Come.
We know from Matthew 13 that the Wheat and Tares will grow together until the 'harvest' at the end of the age. Evil will wax bold but cannot ultimately prevail.
In terms of attitude and posture we can look back over Church History and see a beautiful bride dwelling in the wilderness, a surviving remnant, a work of the Holy Spirit that wrought heavenly victory through great and terrible adversity. It has nothing to do with the rise and fall of civilization, wealth or power.
The Postmillennialist cannot see this. He looks back over the course of history and sees darkness and defeat. He believes thus far the Church has failed in its task.
Since the Kingdom has been more or less equated with Western Christendom it is tragic that many of the moments they would find more glorious and God honouring are in fact the most tragic and in some cases the most sacrilegious and evil.
Embracing what can only be called worldly-wisdom the Postmillennialist cannot see the glory and beauty to be found in the faithful remnant emulating its Lord and Master by taking up the cross, defying the world and suffering to the glory of God. Defying the City of Man and its overlord we declare we are citizens of a Kingdom....not of this world.
The servants of Hades rage against the Truth and its followers who live by love and forgiveness. They seek to establish their gates and nothing pleases the Adversary more than when the followers of Christ turn from the faith, lay down the sword of the Spirit and take up the earthly sword. Then they are easily defeated or even better become unwitting slaves to the darkness.
The victory is not found in this age.
Even so, come Lord Jesus.