Well alright, probably more ink has spent on this chapter than almost any other chapter in the NT (and it’s not like Paul is foreign to difficulty). I will not claim to have brilliant insight here when there have been many smart people who love Jesus who can’t agree on it. However, I do think we can try to put some borders around it, contain the discussion within viable bounds and then let the uncertainties that remain do so within those confines. 
 
The beginning of this chapter seems to be the primary reason for this second letter to the Thessalonians. Even though Paul discussed this at the end of the 1st letter, they simply can’t seem to let it go and are concerned that the Day of the Lord has come without them knowing it. Now, we know from folks like Amos and Malachi that the Day of the Lord was traditionally used to describe a time when God would show up and intervene, generally in the context of redeeming his people or punishing their enemies. 
 
Some folks try to say that Paul is using the Day of the Lord in this way, separate from the return of Jesus. However, that flies in the face of context since v.1 talks about “concerning the coming of our Lord Jesus Christ…” It really couples these two things together in this case, so I think that is the basis of the start of the conversation (but not necessarily the end). In either case, they need to chill out. If the 1st letter to these cats taught us anything, it’s that you won’t freakin’ miss the coming of Jesus (trumpets, and angels and all this). Someone is trying to influence them to believe ridiculous things and Paul is reminding them to not be deceived by spirits or words or writings that aren’t from the bros or doesn’t agree with what they’ve taught them.
 
Now, we need to read what comes next in context of what Jesus said in the Olivet discourse (Matthew 24). From that, we know that there will be signs of the destruction of the Temple and after that no additional signs before Christ’s return. Certainly Paul was familiar with this. So, he says Jesus will not return unless the rebellion comes first and some dude of lawlessness is revealed who thinks he’s hot stuff and an object of worship and takes his seat in the temple of God, proclaiming himself to be God. Further, Paul seems to think the Thessalonians should remember what he already told them and that they remember what is restraining this guy so that he may be revealed in his time (and the process has already started). And the restrainer will only do so until he doesn’t, basically (not helpful, right?).
 
The work of the man of lawlessness is by the influence of Satan, allowing him to do false signs and wonders that deceive those who are already dying because they refuse to believe the gospel. And God allows them (even is part of allowing that to persist) so that they believe false things in order that they will be condemned because they refused to believe the truth and had pleasure in unrighteousness. (If there’s a tie to the 1st chapter, this group is also part of the persecution of the church, the trouble the Thess. church is suffering under). 
 
Ok, so things to consider. Although easy to move all of this to some time in the long future, I don’t think the language or context will allow that. First, the lawlessness fella takes his seat in the temple of God, which will be gone in 30 years. To get around this folks say that the temple is either not really a temple (but instead God’s people) or that it is a rebuilt temple (in fact, this section underlies much of why people think a temple needs rebuilt, coupled with some stuff in Revelation). Although I might be willing to consider “temple as God’s people” in apocalyptic literature (in Revelation, for example), the action of “taking a seat” and the existence of a literal, physical temple at the time without additional clarification here doesn’t really seem to make sense. Sounds like a literal temple which means it needs to sit in their current context. 
 
Further, Paul says they know who the restrainer is. I mean, again, I suppose that could be something that they know that could be true for hundreds or thousands of years later, but it seems to be a person and they understand (or should have remembered) that it will only be for a time. And the mystery of lawlessness is already at work. I have to bring a lot to the text to assume that it is something that isn’t relevant to them at their time. As a matter of fact, unless they have completely forgotten all of whatever Paul said to them on this subject in the past, it seems reasonable to think that their concern that the Day of the Lord has already occurred must be supported by the thought that this man of lawlessness business has already taken place, which means from what they know they must believe that it was possible for it to take place already (vs. something that is obviously happening far from then.) 
 
Also notice that when the description of Jesus shows up to kill this lawless one with the breath of his mouth, we don’t hear anything more about his second coming. In fact, nothing more addresses Jesus returning for his people after the 1st verse. Seems a bit odd if this whole killing of the lawless man action is happening at the same time to not reinforce at some point here or later in the letter the very thing they seem concerned about. But it doesn’t happen.
 
Why not? Because this isn’t the sure sign of when Jesus will return, it’s a sure sign of the one thing that Jesus said has sure signs…the destruction of the Temple. For me, I think the right barriers are that 1.) all of this is happening in their lifetime 2.) it’s not connected to Jesus’ second coming and the end of the age 3.) the man of lawlessness, the restrainer, and the rebellion are all people/things that happen as part of the destruction of the Temple. 
 
Are there options that fit this? Nothing that’s a slam dunk. There’s a Jewish dude, John of Gischala, who led the zealots who eventually overtook the Temple, killed off a ton of the Jews who wouldn’t join the fight against Rome, starved the people of Jerusalem and did a bunch of other junk that I think makes sense. Some folks think the man of lawlessness is one of the Roman emperors. I’m open to options here, but I think our walls are the right ones. 
 
Some people try to tie this man to a future Antichrist or a church tribulation, but as we saw in John’s letters he thought there were multiple anti-Christ’s and they were active and about during his time. John, in Revelation, also said the tribulation was happening at his time as well. So, any consistency there is generally not an affirmation of some sort of future big event just as Jesus returns. 
 
The last section of the chapter is an encouragement of their security in Jesus and to stand firm and hold to the true teachings of the gospel they heard. Further, they ask God to comfort them in this time of persecution and give them the energy and will to pursue every good work and word.
 
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