(3) Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; (4) Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
(7) For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way. (8) And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: (9) Even him, whose coming is after the working of Satan with all power and signs and lying wonders, (10) And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. (11) And for this cause God shall send them strong delusion, that they should believe a lie: (12) That they all might be damned who believed not the truth, but had pleasure in unrighteousness. King James Version Change Bible versions
A major question about II Thessalonians 2 is the scope of the described events. One interpretation is that it is a localized occurrence, in the sense of it happening just within the “little flock”—the church. A second interpretation is that since “the falling away” contains the definite article, it refers to a unique event in man's history, far greater than anything that has happened before. In contrast, the church has had periods of strength and weakness all throughout its history—it goes through cycles of rallying around truth and then gradually letting it slip. This second, universal interpretation is a better fit because, when we look at the whole passage, the events and personalities are worldwide in scope.
Remember, this falling away sets the stage for the man of sin, who will have tremendous influence over humanity. Paul is not writing about apostasy in a small group of people that will give rise to an international personality, but an event on the world scene that creates the right environment to catapult this figure, backed by the power of Satan, to the heights of power.
Paul, then, is letting the church know that it need not be concerned about missing the end time. The events leading up to the Day of the Lord will be unmistakable to those with eyes to see. What will happen will affect the entire world, even though the world will not grasp the spiritual significance.
A falling away is taking place right now. Whether it turns out to be the falling away remains to be seen. Right now, though, we are witnessing a steady defection from the basic principles of the Bible, away from what we call the Judeo-Christian ethic. This is not brand new, but it is picking up speed. We need to be reminded of it because it can have a detrimental effect on us.
Apostasy is a defection from truth—a forsaking of one spiritual approach in favor of another. In the Old Testament, many of the kings and eventually the whole nation of Israel rebelled against Godand chose opposing belief systems. We are seeing the same thing today, but at times, it is harder to recognize because we are accustomed to it, and it is not happening overnight. In the books of Kings and Chronicles, we can read the record of a given king who turned away from God and served the Baals, and the foolishness sounds quick and casual because we are reading a summary. But when a falling away happens around us, perhaps even beginning before we were born, it is easy for our minds to adjust to the point that we almost forget the continuing rebellion against God and His way.
— David C. Grabbe