This, the fourth of the personal letters of Paul, differs from the other three, as well as from all other epistles of Paul, in that it is neither doctrinal, nor intended for general church instruction. It has its interest in that it shows by a particular example the application of the great principles of Christian brotherhood to social life. It is written to Philemon, an active Christian of Colosse, a convert of Paul, in behalf of Onesimus, a runaway slave of Philemon, who had found refuge in Rome, had in some way been brought under Paul's instruction during his first Roman imprisonment, and had been brought to Christ. In Col 4:9 he is mentioned as belonging to Colosse, commended as a faithful and beloved brother who had been of great service, and it is there stated that he would return from Rome to his old home along with Tychicus, while this epistle explains the occasion of his return, and throws a practical light on the new relations of master and slave, which could not be done by precept alone.
Onesimus, an unconverted slave of Philemon, had fled, whether after or before his master's conversion, is unknown. When he was converted the principles of Christian teaching would require him to return, but the conditions of his return are explained in the affectionate letter which he carries back to Philemon. He returns a servant, but as a more than servant, "a brother beloved, both in the flesh, and in the Lord," and Philemon is desired to so receive him in a tender appeal to his consciousness of how much he owes to him who asks. He is reminded that Onesimus is Paul's own son in the Gospel, as well as himself. A sense of the fault is exhibited, and forgiveness for the offender is required, not by the authority of apostolic power, but of love.
This epistle must have been written about the same time as that to the Colossians, and was carried by the same messengers. Its genuineness is accepted by almost all critical authorities, the rationalist Baur being the only notable exception.