Corinth is distinguished, both in this letter and in 1 Corinthians, with the unique address to the church of God. The singular church, in contrast to the more commonly found all and saints, focuses attention on the unity of believers in the Corinthian locality. Of God emphasizes divine ownership—an ownership that differentiates the church from a culture and society that were centered on idolatry (see the introduction).

It was common in Paul's day to include others beyond the immediate readers as independent witnesses of a letter's content and reception—somewhat like the function of our notary today. In the case of 2 Corinthians, all the saints throughout Achaia are called on to verify Paul's claim of apostleship—a claim that has been challenged from both inside and outside the Corinthian church and which, as we will see, Paul is at pains to defend throughout the letter.