2 Thessalonians 2:1-3 Apostasy or falling away from the truth

2 Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him,

² That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
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;
-2 Thessalonians 2:1-3 King James Version (KJV)

This refers to the early Christian Church's falling away from the truth as seen in the Roman Catholic Church before the inner Spirit World's Judgement Day in 1757.

...the Lord is to-day too carrying on the process of redemption, which began with the accomplishment of the Last Judgment in 1757. This redemptive process has continued from that time down to the present. The reason is that to-day the Second Coming of the Lord is taking place, and a new church is to be established, something which could not happen unless the conquest of the hells and the ordering of the heavens had taken place first. Since I have been permitted to witness all that has happened, I am able to describe how the hells were conquered and how a new heaven has been founded and arranged, but it would take a whole book to do so. However, I did reveal how the Last Judgment was carried out, in a small book published in London in 1758. True Christian Religion #115 by Emanuel Swedenborg

If you are interested you can read in this blog site: Book of Revelation: Judgment Day explained in the BLOG ARCHIVE 2013 December at the beginning of Revelation.