In discussing the differences in Reformed Eschatological views, I’ve been asked to defend the postmillennial view against the more popular Amillennial view. The challenge here is to clearly define views that, over time, are slowly evolving into each other, particularly with the rise of "optimistic Amillennialism". The similarities are as follows:
1.) All modern Amillennialists (with the exception of Hyper-preterists) are Postmillennial in the sense that they believe that Christ will return after the “millennium” which they would define as the current church age.
2.) Most (if not all) modern Postmillennialists are Amillennial in that they don’t believe in a literal “millennium”. However, they do hold to a future millennial age (not necessarily 1,000 years) in which the conversion of “Israel after the flesh” will lift part of the curse on Creation.
In the past, however, these two schools had greater differences. Amillennialists have historically been pessimistic about the future of the gospel. In the early church, both chiliasts and amillennialists held that the Roman Empire would wax worse and worse, until the last and worst emperor of all (antichrist) would eventually be destroyed by Christ's Second Advent.
A similar timeline would be suitable for classic postmillennialism as well, with two major differences. The first is that early postmillennialists were more likely than Amillennialists to suggest a date for the Second Advent due to the belief that they were already in the literal millennium. The second difference is, unlike the other eschatologies, postmillennialism was optimistic about the effects of the gospel in the "church age" (though most did hold to a future antichrist).
Preterism in some form had advocates among the earliest Christians such as James the Just, Mathetes, and Clement of Alexandria. However, it was Eusebius who first wrote the most complete work of systematic Preterism. As a backlash against some of the dispensational folly in much of evangelicalism today, Preterism has made huge inroads in Reformed circles. As a result, both Amillennialism and Postmillennialism have made huge strides toward becoming one eschatology. Postmillennialists have long since abandoned their chiliastic roots. Very few believe in a literal millennium today. Much of Amillennialism has adopted a more optimistic view of the gospel, realizing that "tribulation" of the First Century saints was the greatest that shall be faced by the church. The cause for this optimistic view of the future was a return to Scripture as the source for eschatology as opposed to newspapers.
Therefore, modern postmillennialism and “optimistic Amillennialism" are almost indistinguishable, yet there are still some differences, particular with nature and role of God's kingdom in this world, as well as the future state of the world at the Second Advent.
As we examine these differences, perhaps some Amillennial Preterists will find themselves agreeing with the postmillennial camp, and thus objecting to my "broad stroke" labelling. Be assured that the conclusions I have drawn come from leading amillennial authors, and direct quotes will be given as much as possible.