Author, Addressee and Time of Writing
Paul's epistle to Philemon is one of the few books in the NT whose authenticity has hardly ever been doubted. Paul mentions his own name three times in this his shortest epistle (verses 1.9.19). Twice he speaks of being a prisoner of Jesus Christ. He mentions this also in his other "prison epistles" (Ephesians, Philippians and Colossians).
Philemon is not mentioned anywhere else in the NT. The epistle shows that he was a believing Christian and an esteemed acquaintance of the Apostle. The Epistle is addressed to Philemon, with the church in his house, and to sister Apphia and Archippus. Archippus is also mentioned in Colossians 4:17. This shows that Philemon lived in Colossae. In Colossians 4:7-9 we learn that Onesimus was from Colossae also.
The Epistle was written at the same time as the Epistle to the Colossians, that is 61 to 62 AC, from Rome. In both Epistles Paul mentions his imprisonment and gives greetings from Ephaphras, Marcus, Aristarcus, Demas and Luke. In Colossians the believers are informed that Tychicus, who was the deliverer of the Epistle, was accompanied by Onesimus.
Tertullian (around 160 to 220 AC) and the Muratori Canon (end of 2 nd century) testify that the Epistle was written by Paul.
2. Subject and purpose of writing
This Epistle has often been called a "private" epistle of the apostle. But the mention of the church in Philemon's house shows that the personal circumstances of the Christian are not to be separated from the fellowship of the believers, as they are members of one body (Ephesians 4:25). Onesimus was Philemon's slave who had run away and thereby probably stolen money of him. On his flight he met the imprisoned apostle Paul in Rome and was led to faith in the Lord Jesus by him. This is why Paul calls Onesimus "my son" in verse 10. Onesimus might have known Paul by hearsay. Meantime he had become quite helpful to the apostle in various respects (see Colossians 4:9).
But Paul wanted Onesimus to put things right which he had inflicted upon his master Philemon. This is why he sent Onesimus with Tychicus to Colossae and handed them the Epistle. In the Epistle Paul does not write on the Christian doctrine neither does he mention his apostleship nor his authority connected with it. Paul does not plead for Onesimus' release either but gives an example of the spirit of grace and love with which difficulties in daily matters among brethren might be solved. This grace overcomes social differences (compare Colossians 3:11) and past guilt (compare Colossians 3:13). Martin Luther has said of this Epistle: "This epistle is a masterly sweet example of Christian love."
3. Peculiarities
The Problem of Slavery
Slavery was a fixed component of the social and governmental order in antiquity. A slave was considered a "thing" and therewith the sole property of his proprietor. A run-away-slave as Onesimus was had to fear most severe punishment.