What does 2 Thessalonians 1:12 mean?

Continuing the thought begun in verse 11, Paul cites the goal of his prayers for the Thessalonians. It is that the name of the Lord might be seen in and through them. The "name" of Jesus refers to who Jesus is, His character and what He does. In other words, Paul and his coworkers were praying that the Thessalonians' lives would reflect Jesus in all that they did, in their character and conduct. Paul held this desire for his own life. Later, while undergoing a lengthy courtroom trial that would result either in his freedom or his execution, he testified that it was his "eager expectation and hope that … Christ will be honored in my body, whether by life or by death. For to me to live is Christ, and to die is gain" (Philippians 1:20–21).

Paul concludes 2 Thessalonians 1:12 by making it clear that only the grace of God and the Lord Jesus Christ could bring about the kind of life that reflects Jesus' character and conduct. No one can lead a Christ-like life in his own strength; it requires God's grace.