Are the harlot, “Babylon the Great” from Rev. 17:5, and “Babylon” from 1 Peter 5:13 synonymous?
Probable Answer: Yes.
With respect, I am responding to this from an amillennial perspective. I do not claim to be an expert on the Book of Revelation, but I have learned a few things about biblical symbolism.
Apparently, that may be unpalatable to some, which seems a great shame. So be it: I accept that responsibility since I find the amillennial view to this highly symbolic work fascinating.
Somewhat recently, I encountered a few, those with whom I am in agreement doctrinally, state that the second half of Revelation is a reiteration of the first half. That is, if you believe the first half is speaking about Jerusalem, so then must the second half be.
Conversely, others will argue that if the first half relates to Rome, then so too must the second.
This seems especially puzzling because it seems to me that the interpretation does not bear this out. There are (at least) two basic questions that disallow this approach in my opinion as I will try to demonstrate.
I. How are the following verses describing Jerusalem whatsoever? (Note that I am not proposing that Jerusalem is not in view in the Book):
Revelation 17:1b-5: “Come here, I [the angel] will show you [John] the judgment of the great harlot who sits on many waters, 2with whom the kings of the earth committed acts of immorality, and those who dwell on the earth were made drunk with the wine of her immorality.” 3And he carried me away in the Spirit into a wilderness; and I saw a woman sitting on a scarlet beast, full of blasphemous names, having seven heads and ten horns.
4The woman was clothed in purple and scarlet, and adorned with gold and precious stones and pearls, having in her hand a gold cup full of abominations and of the unclean things of her immorality, 5and on her forehead a name was written, a mystery, “BABYLON THE GREAT, THE MOTHER OF HARLOTS AND OF THE ABOMINATIONS OF THE EARTH.”
First, it seems very clear to me that the "harlot" beginning in verse 1 is Rome, irrespective of your view of the first half of the Book. The city of Rome "sat on many waters," indeed it is surround by the sea. The reference to "kings of the earth" must surely be those who indulged Rome through their trade and economic cooperation (among other things). Many of them were no doubt subsequently rewarded for their services through receipt of idolatrous Roman abominations and decadent perversions.
I feel it is perfectly reasonable to view the meaning of "[those] who dwell on the earth were [drunk] with the wine of [the harlot's] immorality" as those nations in close partnership with Rome. Again, in verse 3, John sees this atrocious "woman" with seven heads and ten horns, the same woman, Rome -- "The City on Seven Hills", is being portrayed. Many of the inhabitants of Rome were wealthy beyond imagination (in their day), thus the reference to "being clothed in purple and scarlet, and adorned with gold and precious stones and pearls." Their debauchery, based on some historical accounts, knew no limits.
II. Another nail in the coffin for me (against the view the Book is a reiteration of itself) seems to be this: the woman is called "Babylon the Great, the Mother of harlots and abominations." Now, Jerusalem might be considered many things, but it is never referred to as "Babylon." The descriptions in these verses simply cannot apply to Judah and Jerusalem -- in my opinion.
Then, we should not overlook the fact that while in Rome, Peter makes this statement, referenced in the OP:
1 Peter 5:13: "She who is in Babylon, chosen together with you, sends you greetings, and so does my [Peter's] son, Mark."
It is unclear (to me) who "she" is here (not an expert: Mary?), but there is no mistaking Peter's reference to Rome as "Babylon."
Often, certain confusion arises by a passage much earlier in the Book:
Revelation 11:8: "And [the two witnesses' (Moses and Elijah: O/T)] dead bodies will lie in the street of the great city which mystically is called Sodom and Egypt, where also their Lord was crucified."
[NOTE: I have embedded my proposal that the two witnesses were Moses and Elijah, emblematic of the O/T Law. This can be seen through the power granted to them by God when they were alive:
Revelation 11:6: "These have the power to shut up the sky, so that rain will not fall during the days of their prophesying [Elijah]; and they have power over the waters to turn them into blood, and to strike the earth with every plague [Moses]."]
Israel shamefully disregarded the Old Testament (Moses, Elijah) not being satiated by the murder of their own Messiah. The "bodies" of these witnesses symbolically lay in the streets because the degenerate Jewish nation had forsaken the power of God through them. Thus:
Revelation 11:10: "these two prophets tormented those who dwell on the earth."]
Now the passage of Revelation 11:8 above appears to confound many since, upon reading this, they are convinced the rest of the Book is solely about the nation of Israel and no other. However, there can be no doubt that the characterization: "Sodom and Egypt... where also their Lord was crucified" is representative of Israel, another nation of great sin described earlier in the Book.
It is a simple matter of fact that Christ was indeed crucified outside the walls of Jerusalem. I believe the Book should, therefore, be differentiated into two separate judgments: 1) that of Israel, and later 2) that of Rome. This is significant because it helps provide a more thorough interpretation that otherwise represents a great challenge to many.
These and other considerations, beyond the scope of this response that draw the two verses in the OP together, where "Babylon" in both instances is decidedly Rome. The repercussion of this leads me to conclude that (roughly) the first half of the Book of Revelation (chapters 6 through 11 or so) is describing the siege of Jerusalem in AD 70, while the second half (approx. chapters 13-19 or so) is describing judgment against Rome.
Perhaps the eruption of Mt. Vesuvius in AD 78 is partially in view in the latter chapters? Whatever the case, God brings judgment against Rome as well as (much earlier) Israel. It would have been easier if the passages under consideration occurred earlier in the Book for the purposes of this discussion.
For those who do have an interest in such symbolism, I have offered my 2¢ on the matter.