In 1 Thessalonians 5, who will not be caught up to meet the Lord in the air?
The unbelieving world is the group left out of the rapture of the church. In 1 Thessalonians 5, the text contrasts believers, whom the writer includes with himself as those caught up in the clouds, with unbelievers, who remain outside that gathering to the Lord.
Les explains that 1 Thessalonians 4:17 describes the rapture of the church: believers who are alive and remain are caught up together with the other believers in the clouds to meet the Lord in the air, and so shall we ever be with the Lord. He notes the pronoun "we" includes the writer with other believers, not unbelievers. Then in 1 Thessalonians 5, Les calls this the other side of the coin: those who will not be caught up are the unbelieving world. Chapter 5 begins with the day of the Lord coming as a thief in the night, when Christ will come in wrath and judgment, and the pronoun changes to "they," showing the difference.