The 2Ts 2,1-17 pericope is one of the most difficult passages to interpret in the New Testament. Its Greek is known to be irregular and inaccurate: many elliptical phrases, obscure terms and disconcerting linguistic turns. Furthermore, the whole matter is presented so vaguely that it is not easy to clarify. In this article, the historical, literary and textual contexts of the pericope will be investigated. The sentences will also be analyzed: ἡ ἡμέρα του κυρίου; ἡ ἀποστασία and ὁ ἄνθρωπος της ἀνομίας for being in connection with the participatory phrases τὸ κατέχον and ὁ κατέχων. Finally, it will be suggested that the author of 2 Thessalonians did not claim that the identification of τὸ κατέχον and ὁ κατέχων could be known to readers outside the community of the original recipients. The key to understanding written teaching was reminiscent of an oral speech: οὐ μνημονεύετε ταῦτα ἔλεγον ὑμῖν. The modern interpreter does not have that key.