Our text gives more details concerning the “son of perdition” (3) whose coming predated the final day of judgment. While the passage is a difficult one, the previous teaching that Paul had given to the Thessalonians when he was with them (5) would have made it clearer to them.
For us, it is important to note that the day of the Lord hadn’t come because the “son of perdition” had not yet been revealed. This individual, whoever he was, was to be defeated before the day of judgment. Up to that point, something (we do not know exactly what) had been holding back the revelation of the “son of perdition.” It has been suggested that some power (maybe God, maybe Satan) has held him back, but when revealed, God would defeat him.
Regardless, he would deceive many before his fall. This is the reason Paul wrote his letter. He wanted warn of the danger, and dispossess some of the view that the day of the Lord had come. He was successful on both counts.
