The greeting with which this letter begins is almost identical with that of 1 Thessalonians, and gives the impression that the two letters must have been written from the same place and within a short time of each other. And indeed, they are very similar in other respects also – so similar, in fact, that it has often been doubted whether they could originally have been intended for the same congregation, or even whether they could both have been written by the same author; for how, it is said, could anyone have written two letters within a short space of time to the same people and used whole sentences in the second letter which are taken almost verbatim from the first? At the same time there are notable differences between the two letters. The treatment of questions about the “coming of our Lord Jesus Christ” runs on different lines, and in the second letter the tone is somewhat more severe. The problem is to explain both the similarities and the differences.

Various explanations have been proposed. One is that Paul, soon after writing the first letter, received news from Thessalonica which caused him to write off again at once while phrases from the first letter were still running in his mind. Another is that the two letters were originally written to go by the same messenger to two different (though probably neighbouring) congregations.