The underlying purpose and focus of this letter is built around a few basic concepts. First, Paul is defending his apostleship throughout, because some had come to Corinth looking to “outdo” Paul. Paul must defend himself, not because he is concerned for his personal reputation, but because those boasting themselves “better” than Paul are doing so to gain a hearing and a following with their distortions of the Gospel. Paul did not desire to see them swayed into error (because of its ultimate danger to their souls and growth), and in so doing we have a variety of sections where we will learn and be taught along with these Corinthians. The importance of the integrity of what we are taught and that of the ministries we participate should be considered highest priority.
Paul had also, at this point, been discouraged because he was not sure where his friend in the ministry, Titus was (II Cor. 2:13). Part way into this letter we see the thrill and waves of encouragement that comes over him as he finally sees Titus (II Cor. 7:6, indicating this encouragement comes from God Who “comforts the downcast”). Part of Paul’s discouragement is also caused by not only their questioning his apostleship, but even his motives in not coming to them directly, and this magnified in their apparent “buying into” what the false teachers were promoting. It is common for such to seek to discredit the message by discrediting the messenger. Interestingly, Paul does not build himself up, but instead, details God’s work in him to make him “adequate” (3:6), and goes on to describe the glories of the true Gospel and, in so doing, demonstrates the numerous flaws of what these other teachers are declaring. He defends his/their approach to the Scriptures in chapter 4 which would lead us to believe that these other teachers are using deceptive methods and interpretive approaches to make their points (which has been an enemy throughout each generation of Church history).
Rather than being ashamed of his sufferings, Paul lays them out as points of honor and uses the discussion to remind them of what is coming (chapter 5) versus living for the “now” and all the comforts and “safe zones” it can provide. He goes on to push personal purity/holiness not being “bound” to unbelievers, instead “perfecting holiness in the fear of God” (7:1). To support this, he encourages them not only in their personal walk, but in their ministerial “walk” by encouraging them to prepare for his coming by readying their gift for the impoverished and persecuted Christians in Judea (and that from the all churches in Macedonia that were suffering themselves), chapter 8. In defense of himself, we learn of his “thorn in the flesh” and his prayer to have it removed. Yet (in chapter 12) he tells of the gracious answer from the Lord that “My grace is sufficient” and that His power “is made perfect in weakness”. The letter ends with Paul’s challenged to them to “test yourselves” to scrutinize whether or not they are “in the faith”. The most dangerous form of deception is self deception!