The Main Theme of the Book of 2 Corinthians is

That One Should Always be Faithful to Christ

Therefore seeing we have this ministry, as we have received mercy, we faint not; But have renounced the hidden things of dishonesty, not walking in craftiness, nor handling the word of God deceitfully; but by manifestation of the truth commending ourselves to every man's conscience in the sight of God.

But if our gospel be hid, it is hid to them that are lost: In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them. For we preach not ourselves, but Christ Jesus the Lord; and ourselves your servants for Jesus' sake.

For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ. But we have this treasure in earthen vessels, that the excellency of the power may be of God, and not of us.

We are troubled on every side, yet not distressed; we are perplexed, but not in despair; Persecuted, but not forsaken; cast down, but not destroyed; Always bearing about in the body the dying of the Lord Jesus, that the life also of Jesus might be made manifest in our body. (2 Corinthians 4:1-10 kjv)

The Second Epistle of Paul to the CORINTHIANS Paul had established the church at Corinth during his first stay there and later wrote the first letter to them concerning the less-than-honorable behavior of some of its members.   Apparently Paul paid them another visit, which was not very pleasant, between the first time he stayed there and the time that this letter was written (2 Cor 12:14; 13:1).   As he traveled through Macedonia (northern Greece) on his way to Corinth (located in Achaia or southern Greece), he met with Titus and discovered that his first letter to the Corinthian church had been received and accomplished much good (2 Cor. 7:5-11). Nevertheless, there were still some serious problems in the church at Corinth, including a faction in the congregation who denied that Paul was truly an apostle of Jesus.   As a result, Paul immediately wrote this letter, probably from Philippi, and sent it on ahead with Titus (see 2 Cor. 8:16, 17; 9:2 - 4). This is believed to have been written about A.D. 54 or 55 only eight months to a year after the writing of the Book of 1 Corinthians, Paul spent the next winter in Corinth as he had planned (Acts 20:2, 3; 1 Cor. 16:5, 6). The Apostle Paul's intense emotions and fiery personality are more evident in this letter than in any other epistle. The Book of 2 Corinthians has only a vague systematic form, and except for Paul's letter to Philemon, has the least emphasis on doctrinal issues. He shared some of his personal experiences such as the vision in which he was "caught up into the third heaven" (2 Cor. 12:1 -4) and his "thorn in the flesh" (2 Cor. 12:7 -9). Paul warned them about certain doctrinal errors, instructed them in matters of duty as Christians, and expressed joy that they had heeded his instructions in the first letter. He also defended his authority as an apostle against the attacks of legalistic teachers who sought to disrupt his work. The main theme of the Book of 2 Corinthians is that one should always be faithful to Christ. [Source for Introduction of chapter: Hebrew Greek Key Study Bible KJV edited by Spiros Zodhiates, Th.D. AMG Publishers, Chattanooga, TN 37422]