What does Revelation chapter 18 mean?
The prior chapter used "Babylon" as a reference to a religious or spiritual corruption. This "religious Babylon" was tolerated and manipulated by the leaders of the world, for a time, but then destroyed (Revelation 17). In John's vision, the leaders of the world seem unphased by the destruction of this spiritual Babylon. This "fall" most likely was complete by the mid-point of the tribulation, when the Antichrist and the False Prophet fully engage in blasphemy and idolatry (Revelation 13).In chapter 18, John's vision shifts to describe the fall of a slightly different "Babylon." In this context, Babylon is a political and economic entity. It is probably also a literal city—perhaps not with that exact name—during the end times. It's common for a capital city to stand in as a reference to a culture, or government, or even a religion. "Babylon," in this chapter, occupies a place somewhere in that range of meanings. The "fall" described here most likely occurs near the end of the tribulation, probably as a result of the horrific bowl judgments described in chapter 16.
An angel proclaims the destruction of Babylon, specifically making mention of her pervasive wickedness. As in other Scriptures, "sexual immorality" seems to have a double meaning here. The Bible often uses sexual sin as a metaphor for idolatry and other forms of false religion. The city-nation of Babylon, in the end times, is not only a hub of commerce and power, but of sin and sensuality, as well (Revelation 18:1–3).
John hears another voice warning "my people" to flee the city. This parallels the Old Testament warning given to Lot to evacuate Sodom in advance of God's judgment (Genesis 19:12–13). Not only does God want "His people" to avoid being caught up in the sins of Babylon, He warns them that tangible judgment is coming and they need to flee. The sins of Babylon are enormous, and her judgment from God will be in proportion to that sin. The rapid nature of this judgment is first mentioned here, then further noted in later verses (Revelation 18:4–8).
In the prior chapter, a "religious Babylon" was said to have fallen, but there was no notable mourning from the leaders of the world. Here, however, the fall of Babylon as an economy is met with grief. World leaders will see—probably both literally and figuratively—the smoke from her destruction, and stay far away in hopes of avoiding the same fate. Once again, the fact that this destruction was swift is a key point of John's vision (Revelation 18:9–10).
Along with political leaders, economic leaders will grieve over the fall of Babylon. This passage lists many of the most precious commodities of the ancient world. The point is not to give a literal inventory of Babylon, but to symbolize her far-reaching and enormous wealth. At some point in the end times, Babylon will go from being outrageously wealthy and powerful to desolate, faster than anyone would have thought possible (Revelation 18:11–20).
John also sees an angel throwing a "great millstone" into the sea. Millstones in that era were made of tough rock, such as basalt. A common millstone might be 18 inches (45 cm) around and 4 inches (10 cm) thick, weighing upwards of 100 pounds (45 kg). What's described here is a "great millstone," meaning one of significant size. Some millstones were so large they had to be worked by livestock, and could weigh thousands of pounds / kilograms. The imagery of a massive boulder being dropped into the ocean parallels the complete and speedy destruction of Babylon. When she falls, all her activities will cease entirely, avenging the persecution and murder of God's people (Revelation 18:21–24).
Chapters 17 and 18 depicted consequences of the tribulation which seem to have happened parallel to the various seal, trumpet, and bowl judgments. Chapter 19 will resume describing a timeline, including the end of the tribulation and the earthly return of Jesus Christ.