Several scholars believe that 1 Corinthians was a circular letter based upon 1 Cor 1:2 (“To the church of God which is at Corinth, to them that are sanctified in Christ Jesus, called to be saints, with all that in every place call on the name of Jesus Christ our Lord, both their’s and our’s.) Kenneth E. Bailey writes:
Paul includes the entire church among his readers. He appears to be doing more than merely reminding the Corinthians that they belong to a larger fellowship, although that is surely part of his intent. Nor is he primarily affirming his authority over all the church, and thereby building his case for the authenticity of his apostleship. Rather, he stresses that he is indeed writing this letter for all Christians everywhere. This helps explain the extensive use of polished rhetoric, and the meticulous construction of the five essays before us. From Paul’s own words we can be confident that Paul means this epistle as a “general letter.” (Paul Through Mediterranean Eyes)
Bailey says that the letter was addressed to “Christians everywhere,” and thereby concludes it is a “General letter” (i.e. circular letter). Other scholars, such as Craig Blomberg, suggests that the “church” in Corinth consisted of several houses, and in this sense the letter was circular. However, that is not quite circular in the sense that other large churches received the letter at its time of composition, which would be true of the Catholic Epistles such as 1 Peter.
I suppose that the historical question is whether the originally intended audience for 1 Cor was Corinthian or beyond Corinth as well. This would make it circular like Colossians, which was also meant to be read by the Laodiceans, and probably Ephesians and the Pastoral Epistles which may have been read to the churches under Timothy’s and Titus’ care.
Not even being a novice on Greek grammar, I would not know if the language demands an inference that the letter itself was literally addressed to “all that are in every place” or whether that quotation is merely a reference to those at Corinth call upon the same God as those in every place. If I had to guess, I would guess that the grammar in the Greek does not demand the former understanding.
One of the earliest Greek commentaries on the book explicitly rejects the idea. Chrysostom writes: “For although the letter be written to the Corinthians only, yet he makes mention of all the faithful that are in all the earth; showing that the Church throughout the world must be one…” Origen also wrote a commentary, but I don’t have access to it, so I do not know if he addressed the question.
By Clement’s time, 90AD or so at the very latest (I favor a date in the 70s) the letter in question, as well as others, were already well known to him and he refers to it by name. So obviously the letter circulated at this point. However, we cannot conclude this is because the letter was originally intended to be circular.
Clement writes, “Take up the epistle of the blessed Apostle Paul. What did he write to you at the time when the gospel first began to be preached? Truly, under the inspiration of the Spirit, he wrote to you concerning himself, and Cephas, and Apollos, because even then parties had been formed among you.” (1 Clem 47) This is our earliest reference to the letter, and he simply says that Paul wrote it to them, with no reference to other recipients. Of course, this is hardly a smoking gun, but it would be a passing observation consistent with how Chrysostom sized up the intended audience.
I think the best evidence we have that the letter is not circular is from 2 Corinthians. 2 Cor 1:1 states, “To the church of God which is at Corinth with all the saints who are throughout Achaia…” This increases the probability that 1 Cor was addressed to an audience localized to a specific geography. There are good reasons to believe this, but it takes looking at a map to appreciate this.
Corinth was the only mainland Greek (i.e. Achaian) city which we know had a major church during Paul’s lifetime, as no major church was known to be planted in Athens or Cenchrea. Further, it was the only Greek church in Greece to receive an Epistle by Paul. Lastly, the city was the Roman capital of the province of Greece. This would mean that Paul would be able to address all of the churches big and small in the whole region by simply addressing Corinth, as it was the hub for all of Achaia.
A final note. I find it hard to believe that Paul would address 1 Cor circularly, because he not only airs all of their dirty laundry, he also includes implicit praise to the Macedonian churches in 1 Cor 16 (and explicit praise for them in 2 Cor). For one, this publicly shames the Achaian churches in the eyes of all–not that they didn’t deserve it though. Second, this gives the Macedonians a big head. It just does not seem to make sense contextually.
So, without a grammatical, contextual, or geographical reason to believe 1 Cor was circular, I’ll stick with the first explicit commentaries on its origins which simply presume that it originally had a Corinthian audience and no other.