A short letter that warns its readers not to be taken in by a forged letter claiming to be from Paul — and whose own authenticity is disputed. That irony is not a joke; it is the central problem of the book.
What the book is
2 Thessalonians encourages a congregation under pressure, corrects a belief that the day of the Lord had already arrived, describes a sequence of events that must happen first, and instructs the community about members who had stopped working.
It is short, formal, and closer in structure to 1 Thessalonians than any two Pauline letters are to each other.
How it is put together
The letter follows the outline of 1 Thessalonians closely — two thanksgiving sections, a central teaching block, closing instructions — while differing in tone. Where the first letter is warm and personal, this one is measured and official.
The central passage in chapter 2 describes a sequence: a rebellion, the revealing of a figure of lawlessness, a present restraint that must first be removed. What the restraint is was already obscure to the earliest commentators who discuss it.
The authorship question
This is one of the more finely balanced disputes in the New Testament, and both sides argue from the text.
Against authenticity: the eschatology conflicts with the first letter, which says the day comes like a thief with no warning, while this one supplies a sequence of prior signs; the style is more formal and more dependent on set phrases; the structural imitation of 1 Thessalonians is closer than Paul’s letters usually are to one another; and chapter 2 warns against a letter purporting to be from Paul, while chapter 3 draws attention to a signature as a mark of genuineness — a move that would suit a forger particularly well.
For authenticity: the attestation is early, the two eschatological passages address different questions and need not conflict, and a follow-up letter written soon after the first would naturally reuse its structure. If Paul wrote it, it belongs to about 51 CE. If not, it belongs somewhere in the following decades.
This site does not resolve it, and treats the question as genuinely open rather than settled in either direction.
Where the external record touches it
Nothing external attests the letter or its contents. The only relevant external material is the same civic and epigraphic record for Thessalonica that bears on the first letter.
That is worth stating because the passage in chapter 2 has been applied to identifiable people and states repeatedly over the last five centuries, and the record supplies no basis for any such application. Whatever the passage refers to, it is not something the external record can be used to identify.
Related: 1 Thessalonians, and the method note on what kind of text this is.