Let no one deceive you in any way. For it will not be, unless the departure comes first, and the man of sin is revealed, the son of destruction,
The man of sin ... See excursus on this at the end of the notes on this chapter.  He is the same as the "lawless one" in  2 Thessalonians 2:8, with this distinction, that "the man of sin" refers to a progressive development of an anti-Christian influence, whereas "the lawless one" is thought by many to refer to some terminal and final embodiment of evil.  The interpretation presented here is that the man of sin has indeed appeared.  The man of sin sitteth in the temple; he exalts himself; he is a false apostle, the son of perdition; names of blasphemy are upon his head; and he is drunken with the blood of the martyrs of Jesus; but his course is not yet run.  The final usurpation of the place of God himself has not yet taken place.