Yesterday I posted the Historical Background of Philemon, but you may have noticed there was something missing. Clearly, the issue of slavery is central to the book of Philemon and I included very little information about that institution in the Roman Empire at the time of Paul. I did this intentionally, to single out this issue and approach it with a narrowed focus.
The Roman law of slavery at this time was extremely intricate, and slaves were regularly treated inhumanely and the average condition of a slave was horrendous. Considering the average condition of a slave being horrendous, one can conclude from the following papyrus quote from AD 298 that no practical limits existed for slave masters to express their anger on runaways. “[A]nd when you a [slave-catcher] find him [a fugitivius] you are to deliver him up, having the same powers as I should have myself, if present to […], imprison him, chastise him, and to make an accusation before the proper authorities against those who harbored him, and demand satisfaction.”
We can see in the New Testament that slavery was not yet abolished or opposed by Christians, at this time. Paul instructs both slaves and masters on how to work and behave in Colossians 3:22-4:1: “Slaves, in all things obey those who are your masters on earth, not with external service, as those who merely please men, but with sincerity of heart, fearing the Lord. Whatever you do, do your work heartily, as for the Lord rather than for men, knowing that from the Lord you will receive the reward of the inheritance. It is the Lord Christ whom you serve. For he who does wrong will receive the consequences of the wrong which he has done, and that without partiality. Masters, grant to your slaves justice and fairness, knowing that you too have a Master in heaven. ” As you can see, Paul doesn’t suggest slavery should be banned, nor does he really state he’s opposed to it. He tells the church that slaves should obey and serve both their masters and the Lord. He also tells the church that the masters should treat their slaves justly and fairly, like God treats them.
Given the disrespect paid to slaves by the secular, Roman culture and even the Christian view of slavery; for Paul to request that Onesimus not only be freed, but seen as an equal brother in Christ, (Philemon 16) would have been radical in Roman society at that time.
 McNaughton, Ian S. Opening up Colossians and Philemon (Opening up the Bible). Opening Up Commentary. Leominster: Day One Publications, 2006.