The Bible contains two letters from Paul to the Corinthian church. But it is likely that he wrote at least three letters to them (and possibly four). The two epistles preserved for us in the Bible were the only ones that were inspired by God and thus canonical and worthy of preservation.
In the letter we have designated as 1 Corinthians, Paul mentions that “I wrote to you in my letter not to associate with sexually immoral people” (1 Corinthians 5:9). The natural supposition is that Paul must have written a letter to the church before he wrote 1 Corinthians. He is now clarifying a statement he made in the prior letter to prevent misunderstandings.
There are a few who view 1 Corinthians 5:9 as a reference to the same letter he was writing at the time. This idea is based on 1 Corinthians 5:2, which instructs the Corinthians to remove a sexually immoral man from the fellowship of the church. According to this view, Paul gives an instruction in verse 2 and then refers back to that same instruction in verse 9. Such a circular reference seems unnatural, however. A plain reading of the text leads to the straightforward interpretation that Paul is referring to a different letter altogether.
In the book we call 2 Corinthians, there may be yet another reference to a different letter. Paul says, “I wrote as I did, . . . I wrote you out of great distress and anguish of heart and with many tears” (2 Corinthians 2:3–4a). The letter Paul alludes to here is often referred to as the “sorrowful letter” because of its difficult subject matter, its stern tone, and the pain it caused Paul to write it. The apostle immediately expresses his purpose in writing that letter: “Not to grieve you but to let you know the depth of my love for you” (verse 4b).
Paul refers again to the “sorrowful letter” a few chapters later: “Even if I caused you sorrow by my letter, I do not regret it. Though I did regret it—I see that my letter hurt you, but only for a little while—yet now I am happy, not because you were made sorry, but because your sorrow led you to repentance” (2 Corinthians 7:8–9). Is the “sorrowful letter” Paul mentions in 2 Corinthians 2:4 and 7:8 the same as the epistle of 1 Corinthians? Scholars are divided on the answer. Those who do think that 1 Corinthians is the “sorrowful letter” point to chapters 5 and 6 of that book, where Paul directly confronts a problem in the church and rebukes the Corinthians for tolerating sin in their midst. The anguish Paul had in writing that rebuke shows the kindness and tenderness of his heart, which was broken at having to discipline the church. The majority of commentators take the view that 1 Corinthians is indeed the “sorrowful letter.”
Others don’t think that 1 Corinthians is the “sorrowful letter.” They see 1 Corinthians as certainly corrective and dealing with some difficult subjects, but they don’t see it as rising to the level of causing Paul “much affliction and anguish of heart and . . . many tears” (2 Corinthians 2:4, ESV). Since 1 Corinthians cannot be called a severe or harsh letter (the thinking goes), the “sorrowful letter” mentioned in 2 Corinthians is likely another correspondence Paul had with the church in between the writing of 1 and 2 Corinthians. According to this view, the “sorrowful letter” has been “lost,” since it did not make it into the Bible.
Still another view is that the “sorrowful letter” is chapters 10—13 of 2 Corinthians—chapters written in a decidedly ironic and injured tone. According to this theory, those chapters originally comprised at least a part of the intermediate letter and were eventually merged with 2 Corinthians as an addendum, so as to make one book of the two.
Most likely, there were three letters that Paul wrote to the church of Corinth. The existence of a fourth, intermediate letter is unlikely. If there were four letters, they would have been written in this order:
1. A letter instructing the Corinthian Christians not to fellowship with professed believers who were sexually immoral
2. First Corinthians
3. An intermediate letter, the “sorrowful letter,” that pained Paul to write because of the harsh tone he was required to take
4. Second Corinthians
Again, #3, the intermediate or “sorrowful” letter, is most likely the same as #2, (1 Corinthians).
It is possible that Paul wrote plenty of letters to Corinth and other churches that were never preserved. Not everything the apostles wrote was inspired by God. The books we have of Paul are inspired and therefore part of the canon of Scripture. The Bible we possess today is the complete, divine revelation from God to mankind.