The last book in the New Testament is John's revelation of Jesus Christ. It is prophetic which means it must be interpreted. However, some people think differently than others. It could be said that each way of looking at the symbolism has its share of truth. For instance, the praeterist approach believes that the activities in Revelation are current events with most of them being fulfilled in John's lifetime. That is why the figurative descriptions are difficult for us to comprehend but would have been more understandable to those of that time. The symbolism would have had figurative meaning to them and would have provided comfort because they were contending with the Roman Empire. Perhaps they thought that Nero was the antichrist. But the prophecy would give them a sense of victory over their situation. The historical context would be secondary to figurative lessons taught.
On the other hand, the historist approach sees Revelation as God's prophetic program from the apostles to the end of the age. To them it would be a panorama of chuch history. Descriptions in Revelation have their parallels in church experience and struggles. But they had to connect the symbolism with reality. That could become subjective and it could be reevaluated at another time. A literal interpretation would be more definitive. The futurist postpones the events to seven years before and just after the Second Coming. The dispensationalist sees the temple being rebuilt and sacrifices being restored. Others see King David being resurrected and again places on his throne.
Postmillennialists are a lot like amillennialists. They believe that the Second Coming occurs after the millennium. In the meantime they define the millennium as taking place during this current church age where the spiritual kingdom is unseen but nonetheless in operation. They point out that Satan was bound at the cross so it isn't logical that things will literally get worse and worse. They see the gospel gradually converting the world to Christianity, though not ever to 100%. Sin is gradually erradicated though not altogether. There is no exact 1000 year period, but rather it will take as long as necessary. Liberals see science and the advancement of knowledge as perfecting civilization. But evaluating progress depends on subjective human reasoning which is unreliable. Some activists want to take charge and make the transition more aggressive. The Kingdom Now group advocates that the time for obedience is nigh. The Dominion Theology group stresses that the Bible advocates God's kingdom being the controlling force. But how do you prevent humanism from creeping in or becoming overly forceful?
"A" and "post" millennialists see the church as the new Israel so they don't distinguish between the two. When it says "thus all Israel will be saved" (Ro 11:26) they say it does not mean national Israel but rather an elect number of Israelites. However, Jeremiah had prophesied, "'When I will make a new covenant with the house of Israel and with the house of Judah . . . I will put My law within them, and on their heart I will write it; and I will be their God, and they will be My people'" (Jer 31:31,34). Hebrews refers to it saying "if that first covenant had been faultless, there would have been no occasion sought for a second" (Heb 8:7). Therefore that prophecy applies to Israel and not the church. Paul concurs saying "God has not rejected His people, has He?" (Ro 11:1). He explains to believers "it is not you who supports the root, but the root supports you" (:18). Furthermore, "how much more shall these who are natural branches be grafted into their own olive tree?" (:24). "All Israel will be saved" (:26). "The gifts and the calling of God are irrevocable" (:29).