However, I came across Paul's little digression written to Philemon, and was struck by multiple themes throughout the letter. There are multiple strands in this tapestry that indicate that Paul had a low view of slavery in regards to anything other than Christ Jesus, as we shall see in the end of this post.
Paul wrote numerous times about the abstract theme of liberation. You have him mentioning that the Church of Galatia should "stand firm, then, and do not let yourselves be burdened again by a yoke of slavery" (5:10) and announced the Magna Carta of humanity in Christ "there is neither Jew nor Greek, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus." (3:28). I could go to list instances where Jesus engaged with gender and social barriers but that should suffice.
What we have here are a multitude of rhetorical devices and clever ploys. Paul softens Philemon up by giving him a (culturally standard) thanksgiving, but I think Paul is using far stronger means here than a standard greeting. He is establishing a form of equality with Philemon hence the term "partnership" which can also be rendered as "fellowship" which had religious significance as one of the uses is in relation to the Logos in John 1:3. This is emphasized in Paul calling Philemon "brother."
Consequently, we have Paul using the conjunction "therefore" or "for this reason" to continue his train of thought. Having established his equality with Philemon, he then pulls the social pressure card. "Old man" is a nice way of saying "I've been doing this ministry thing longer than you." Paul states that Philemon must take Onesimus back "forever" (anion) and to call him "brother" in the Lord and a "fellow man."
Paul, however, strips away the dichotomy [of slavery being of social value] in the same sentence by stating that Onesimus is a beloved brother of Philemon both in the material and the spiritual realms(1).
The entire letter is quite awkward to think about, as Philemon simultaneously has been rhetorically tickled and sucker punched. Since Paul intends to come and stay with Philemon in v22, Onesimus can hardly be expected to have his slave greet Paul at the door. Instead, I think Paul recognizes the practical implications of his words in Galatians and works through the conventional means of his day to free a slave. Not only is he risking capital(2) but also his reputation. The parallel passage in Galatians 4:7 indicates that "no longer a slave" should carry more than just "spiritual" equality.
Also, I just discovered the possibility that Ignatius Eph. 1:3 speaks highly of "Onesimus, a man of inexpressible love and your bishop."(3). Though Onesimus was a fairly common slave name, the fact that one with a slave name could become a bishop is of worthy consideration. Contrast this with the Apostle Junia in Romans 16:7, with the possibility that the name Junia carries nobility but could be of slave origin(4).
Just thinking out loud.
1. Payne, "Paul Applies Maximum Social Pressure for Philemon to Free Onesimus" pg1-2.
2. Ibid. pg3.
3. Ibid. pg4.
4. Peter Lampe, "The Roman Christians of Romans 16" pg226.