"Whereunto he called you by our gospel, to the obtaining of the glory of our Lord Jesus Christ."
So all men who are elected by God are called to the Gospel to obtain the glory that is of Jesus Christ.
2 Thessalonians is about the truth being proclaimed by tradition, which is both by word of mouth and by the scripture. In other words, Truth -> Scripture. The relationship between Chruch and Truth is in 1 Timothy 3:15, as well as in several chapters from John.