To me, one of the biggest mistakes that Post-Tribulationists make is to assume that "the day of the Lord" (1 Thess. 5:2; 2 Thess. 2:2) and the event we call the Rapture (1 Thess. 4:13-18; 2 Thess. 2:1) are one and the same. That is to say, they equate the Day of the Lord (1 Thess. 5:2; 2 Thess. 2:2) with "the coming (parousia, 3952) of the Lord" (1 Thess. 4:15; 2 Thess. 2:1). Let me give you an example of what I am saying. Craig Blomberg (pp. 80, 81) writes concerning the parousia (2 Thess. 2:2) as follows:


    But Blomberg completely misidentifies the concern of the Thessalonians which Paul here addresses. The Thessalonians were not concerned that they had missed the parousia. They knew Christ had not yet come, because they were still on earth! What they were concerned about was that somehow they had misinterpreted Paul's teaching or that Paul had been inaccurate. They had been taught by Paul that Christ's coming (His parousia) would precede the Tribulation (the Day of the Lord). But now, they were encountering so much persecution they were beginning to conclude that they were already in the Day of the Lord -- the Tribulation was upon them! In effect, the troubles they were going through convinced them that they were already in the Tribulation, and that the Rapture of which Paul had spoken was, after all, a Post-Tribulation Rapture, not a Pre-Tribulation Rapture.

    The problem is that Blomberg, along with other Post-Tribulationists, makes three mistakes. (1) He fails to recognize that the eschatological parousia of Christ will eventuate in two stages, not one. (2) He assumes that the parousia is identical with the Day of the Lord. (3) He incorrectly identifies the alarm of the Thessalonians. He believes they were alarmed because they had missed the parousia. That is not what Paul said. He identified their fear as being grounded in the misperception that the Day of the Lord, that is, the Tribulation, had already begun (2 Thess. 2:2). So Paul goes into a fairly extensive explanation to correct their false belief -- not that they had missed the Rapture, but rather their false belief that they were already in the Tribulation. He goes on to demonstrate conclusively that the Day of the Lord (i.e. the Tribulation) could not possibly have begun yet because a series of events had not yet occurred (2 Thess. 2:3-12). In other words, Paul was trying to protect the Thessalonians from the very view that Blomberg espouses, namely, that the Tribulation will occur before the Rapture!