First, let me say that there should be no question whether there will be a rapture. Regardless of what one calls it, this passage makes it clear the event will take place:
1 Thessalonians 4:13-18 NKJV But I do not want you to be ignorant, brethren, concerning those who have fallen asleep, lest you sorrow as others who have no hope. (14) For if we believe that Jesus died and rose again, even so God will bring with Him those who sleep in Jesus. (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 by no means precede those who are asleep. (16)
For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first. (17)
Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air. And thus we shall always be with the Lord. (18) Therefore comfort one another with these words.
The only question, then, should be the timing of the event, and that is fine to debate. I am indebted to other teachers (particularly Dr. Tony Garland) for these points, obviously, but that should not detract from whether they are valid points or not.
1) The doctrine of the immanent return of Christ. If the rapture does not happen pre-trib, then there are many events which must take place before the return of Jesus Christ.
2) Populating the Millennial Kingdom: From many passages in the Old Testament, we understand that sinners will inhabit the millennial kingdom. The kingdom is ushered in at the
return of Jesus (Matthew 19:28; Matthew 25:31; Revelation 20:4). The sinners who enter the kingdom are believers who survive the Tribulation and produce offspring who eventually reject the rule of Christ (
Revelation 20:7-9). If the Rapture is after the Tribulation, then where do these people in unglorified bodies come from? If all believers are caught up to meet Christ in the air at the Rapture (
1 Thessalonians 4:17) and are changed (
1 Corinthians 15:52) and only believers enter the kingdom (Matthew 25:34 cf. Matthew 25:46), whence the people producing children in the millennium (
Isaiah 65:20)? Clearly, the believers at Christ's return did not participate in the Rapture or they would have glorified bodies and would be incapable of sin or reproduction. If the Rapture occurs at the Second Coming at the end of the Tribulation (some sort of glorified "U-turn in the sky"), then there are no human beings in natural bodies to populate the Millennial Kingdom.
3) Escaping God's Wrath: Numerous passages indicate that believer's will not be subject to God's wrath (
Luke 21:36;
Romans 5:9;
1 Thessalonians 1:10;
Revelation 3:10). Yet Scripture also identifies the Tribulation as a special time in history connected with an intense outpouring of God's wrath upon those who dwell on the earth (
Revelation 6:16,
17; Revelation
11:18; Revelation
14:8,
10,
19; Revelation
15:1,
7; Revelation
16:1,
17,
19; Revelation
19:15). Although believers have eternal life (past tense) when we believe, we will be saved (future tense) from wrath through Him (
Romans 5:9). This
salvation from wrath speaks of a future time of wrath which believers will not experience. It is a time period which we will not be present to witness—we are saved, not just from the wrath, but from the very hour of testing of the earth dwellers during the Tribulation (
Revelation 3:10).
4) Contrasting Second Coming Passages: When we look at various Second Coming passages, we notice apparent distinctions. In some passages, Christ comes in the air (
1 Thessalonians 4:17). In other passages, He comes to the earth (
Zechariah 14:4;
Acts 1:11). In some passages tribulation begins (
2 Thessalonians 1:6-9). In others, the millennial kingdom is ushered in (
Revelation 20:1-7). In some passages, signs precede His coming (
Luke 21:11,
15). In other passages, no signs precede His arrival (
1 Thessalonians 5:1-3). How do we put all these passages together if they describe one and the same event? It is the same puzzle that the Jews faced attempting to reconcile Old Testament passages which speak of a victorious king (
Psalms 2) and a suffering servant (
Isaiah 53). How do we reconcile these tensions in the Old Testament passages? We understand that they describe different Comings of our Lord: to suffer and die at His first coming, but to rule supreme at His Second Coming. Similarly, New Testament "Coming" passages with consistent contrasts are describing two different events: the Rapture of the Church—when He comes for His own versus the Second Coming in judgement upon an unbelieving and rejecting world. If we ignore this distinction, nothing but confusion will result.
I could add more, but this will suffice for now.