"For the Lord himself will descend from heaven with a cry of command, with the voice of an archangel, and with the sound of the trumpet of God. And the dead in Christ will rise first. Then we who are alive, who are left, will be caught up together with them in the clouds to meet the Lord in the air, and so we will always be with the Lord."These verses have often been used to support an idea known as "the rapture". The rapture refers to the idea that before Christ's return to earth every Christian in the world will suddenly be taken up into heaven. It has been popularized in my lifetime by the Left Behind book and movie series in which a pile of clothes is the only thing left of Christians who have been raptured by God to heaven to be with the Lord. This is usually thought to happen secretively; without any warning, every Christian will simply vanish. There are a number of reasons I don't think rapture is a biblical or theologically sound idea but for now I'll limit myself only to why I don't think this passage from Thessalonians is speaking about rapture.
One thing is very clear in this passage; there is nothing secretive about Christ's return in itself. Those who think of the rapture as a secretive event where everyone will wake up the next morning and notice that all the Christians are gone are often thinking of Paul's language in the next chapter of Thessalonians where Paul compares Christ's return to the coming of a "thief in the night". However, the purpose of that metaphor is not to say that Christ's coming will be quiet and unknown but that the timing of his coming is unknown. No one knows when he will come just like no one knows when a thief might break into their house. However, Paul's language in chapter 4 makes it clear that when Christ comes it will be an event that can not be missed: a cry of command, the voice of an archangel, the sound of God's trumpet, the raising of the dead. Those all seem to indicate a very public event that can not be ignored. This holds true even if these images are a metaphor like the "thief in the night" imagery since the point of the metaphor is that something easily observable and unmistakable is taking place. In fact, if we take 2 Thessalonians into consideration along with this passage, it seems very clearly that much of the intent of Paul's language here is to reassure the Thessalonian Christians that the Lord's coming is something that will be obvious and that they can't miss. While Paul may not be able to describe the return of the Lord exactly or say when it will be, he assures the Thessalonians that they will know when they see it.
But what of Paul's language in the next verse where he speaks of being "caught up together with them in the clouds to meet the Lord in the air"? Doesn't that sound like Paul is talking about rapture? It probably does if we already have the idea of rapture in mind when we come to this verse. However, it seems unlikely that Paul's audience would have understood him that way for at least two very significant reasons. First, the idea of rapture is a young one in the history of the Church. It was first widely published by a man named John Nelson Darby in the mid-1800's. If rapture is the obvious way of understanding this passage then its difficult to see why the all the Christians who lived in the 1800 years of Christianity prior to Darby didn't understand Paul this way.
Even more significant is that the words translated as "to meet" (eis apantesin in Greek) in the phrase "to meet the Lord in the air" are not just generic for any meeting of any kind. It is a technical phrase that was used in Greco-Roman culture for the meeting of a city delegation with a VIP or dignitary who was visiting that city. In this custom, the delegation of important and influential people from the city would go outside the city gates to meet and welcome the visiting dignitary. The purpose, of course, was to welcome them into the city, not remain outside of it or go somewhere else. The very reason for the delegation was to honor this great person as they entered their city. It seems very likely that as people living in this Greco-Roman culture that the Thessalonians would have heard Paul making an allusion to this specific practice. In that case, the purpose of the meeting with the Lord in the air is not so that Christians can continue on to heaven but so that they can welcome Jesus to earth where his reign and kingdom will now be established in its fullness.
What is most important, however, is that we recognize that Paul's theological reflection on Christ's return in these verses is not mere speculation about the future. Instead, these are words of comfort to those who are grieving in the midst of death. Paul is not helping the Thessalonians make a timeline chart of the end of days. He is writing to a people who have been confronted with the death of their loved ones and are wondering how that death relates to their new faith in Christ as Lord. Interestingly, Paul's words of comfort say nothing of heaven or going to a better place. Instead, Paul's hope for those who have died is that the same power which raised Jesus from the dead will raise them as well so that they can participate in the kingdom of righteousness and peace which Jesus will establish. The Christian hope is ultimately not that we will escape the evils of this world but that God will purify this world of its evil and make all things new.