This article offers insights into the issue of the integrity of the First Letter to the Corinthians whose compositional unity has been challenged. On the one hand, we have supporters of the integrity and the compositional unity of the letter, and, on the other hand, we have supporters of various partition theories that view the letter as a compilation of many different original letters and emphasize its composite nature. The main goal of the article is to fortify the position of a unified literary composition that can be easily understood even without the divisive partition theories. The structure of this work discloses an additional intention to differentiate between the issue of authenticity, which deals exclusively with the person of the author, and the issue of integrity, which is concerned with the composition of the letter. The first part provides a brief examination of the authenticity and supplies both external and internal evidence in its favor. Whereas Paul’s authorship has not been seriously doubted, the unity of the letter has been questioned by many scholars, even though most modern scholars support the integrity (unity) of the letter. The second part lays down the main points of various partition theories that view the letter as a compilation of many letters and of a middle ground hypothesis that wishes to take a neutral stand by suggesting different editions of the letter. However, the latter hypothesis appears to be only a variant of the composite theory since the end-proposition suggests that First Corinthians is a twofold composite letter. Each of the two groups of proposals receives significant responses from the supporters of the integrity who refute the scarce evidence by the former and offer further evidence in favor of the literal unity of the letter. The third and final part synthesizes and expands the claims of the letter’s integrity and underlines its unified composition. In addition, it conveys the results of a literary-rhetorical analysis that provides a convincing rhetorical and epistolary structure of First Corinthians which demonstrates both thematic and rhetorical unity of the letter when regarded as a unified deliberative letter urging concord. The concluding synthesis emphasizes the fact that the middle ground hypothesis is still in the search of its supposed neutral position and that the partition theories still lack convincing and conclusive evidence against the integrity and unity of the letter. The multitude of often contradicting partition hypotheses and similar attempts to explain the letter as a compilation of many letters or as a product of different editions represents the best evidence against their validity. This article emphasizes that the present letter that we have at our disposal is not a compilation of many letters, but a single non-composite document that Paul the Apostle himself originally wrote, even if it was written over an extended period. In the final instance, as long as the First Letter to the Corinthians remains intelligible as a whole and as long as it successfully transmits Paul’s authentic message of the Gospel of Christ, there is no need for partition hypotheses, they become obsolete.