In the Christian New Testament, there were false teachers who had taught (during the First Century at the time of Paul) that the resurrection had already taken place.
2 Timothy 2:17-18 (NASB)
17 and their talk will spread like gangrene. Among them are Hymenaeus and Philetus, 18 men who have gone astray from the truth saying that the resurrection has already taken place, and they upset the faith of some.
Some believers were upset, because they believed that they were excluded from this resurrection. In other words, the hope of the resurrection relates to believers both alive and dead, and to be excluded from this resurrection would imply that you were not saved in the first place.
John 14:1-3 (NASB)
1 “Do not let your heart be troubled; believe in God, believe also in Me. 2 In My Father’s house are many dwelling places; if it were not so, I would have told you; for I go to prepare a place for you. 3 If I go and prepare a place for you, I will come again and receive you to Myself, that where I am, there you may be also.”
There is no indication that there is any discrimination between living and dead believers. That is, all those who believe in Jesus are in mind. When Hymenaeus and Philetus were teaching that the resurrection had already occurred, they were contradicting the words of Jesus - that is, they were making Jesus to be a liar.
1 Timothy 1:19-20 (NASB)
19 keeping faith and a good conscience, which some have rejected and suffered shipwreck in regard to their faith. 20 Among these are Hymenaeus and Alexander, whom I have handed over to Satan, so that they will be taught not to blaspheme.
If we connect the Hymenaeus from 1 Tim 1:19-20 to the very (same?) Hymenaeus mentioned in 2 Tim 2:17-18, then the blasphemy appears to be in making Jesus to be a liar in that not all believers are included in THE resurrection (as Jesus had made the explicit promise in John 14:1-3, noted above).
Again, later in the First Century, as Paul began was writing his epistles, many people who heard these words of Jesus had already begun to die.
1 Corinthians 15:6 (NASB)
6 After that He appeared to more than five hundred brethren at one time, most of whom remain until now, but some have fallen asleep.
Thus when Paul talks about the resurrection in his epistles to the Thessalonians, there is no change of scope in the text that would separate living believers from those believers who are already dead. In other words, the event of the resurrection of believers includes those living and those dead.
1 Thessalonians 4:15-18 (NASB)
15 For this we say to you by the word of the Lord, that we who are alive and remain until the coming of the Lord, will not precede those who have fallen asleep. 16 For the Lord Himself will descend from heaven with a shout, with the voice of the archangel and with the trumpet of God, and the dead in Christ will rise first. 17 Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord. 18 Therefore comfort one another with these words.
The last verse here begs the question: How do you comfort somebody with the message of the resurrection, when, if perchance you happened to be alive when it happened, you would have to remain behind (for whatever reason)? The issue here therefore is not about “rapture” or “tribulation.” That is, this resurrection will include all those who are (or had been) believers. Thus when this resurrection occurs, we have comfort (now in the present moment today right now) that we will have immediate corporal reunion with the Lord and with those loved ones who had preceded us in the Lord.