In the Greek world everybody knew the word -doulos- could belong to two quite different models. A person could be a slave or a paid servant. But it was impossible to tell from a person's appearance which model was operative. A slave could be doing very responsible work such as accounting, writing a book, or running a business. And like a hired hand a slave could be paid to buy his own food, and enjoy other minor freedoms. The difference was that a servant could choose to leave and work elsewhere. If a slave ran away the penalty was death or at least a very severe beating.
Another model that governed social situations was whether a person was a Roman citizen. And you could be a citizen by birth, or you could acquire that status by -pollou kephalaiou- a huge cash payment (Acts 22:28). But there again there was no way to tell by looking what you were. People soon found out.
Philemon, the writer of the letter, was obviously a slave owner, and -Onysimus- meaning Useful had been his slave. Useful could have been taken prisoner in war and sold to Philemon as a slave, or he could have been born in Philemon's villa, or he could have been bought and sold several times. A Roman citizen could not be enslaved, so we can assume that Useful had never been a Roman citizen. His owner could be either a freeborn Roman, or a citizen by payment of money, or a slave owner who was not a Roman citizen.
When an -ekklesia- began functioning as a church in a city the dynamic of another model burst in on the scene. Roman citizens and non-citizens, employers and employees, slave owners and slaves, could equally be baptized and welcomed to communion. But that raised huge problems. A master and his domestic servants could find themselves taking communion at the same table.
Rearranging the social niceties in that case was hard enough. In nineteenth century England Anglican servants went to Evening Prayer. In the American South black employees soon developed their own congregations, and eventually they formed new denominational groupings.
The fact that slaves belonging to other people attended one's Eucharist was strange but not impossible to cope with. Having one's own slave as a fellow member of the Body of Christ would at first have been unbearable to cope with. But the unthinkable became a necessary part of the new model Jesus was using to build his church. Among the baptized there was -ouk eni Ioudaios oude Ellyn, ouk eni doulos oude eleutheros, ouk eni arsen kai thylu- which meant very simply that Jews and Greeks, servants, slaves, and slave owners, women as well as men, all had to welcome one another to communion and free each other to exercise their gifts in the Body of Christ (Galatians 3:27-28).
And there were no ifs and buts. The Philippian jailor, who was probably a Roman citizen, had an earthquake conversion at midnight. It seems all the household servants and slaves, and men, women and children of whatever nationality were baptized by breakfast (Acts 16:33). By Sunday they would be sharing in the communion service of the second congregation of the - ekklesia- in that city. No wonder the two Romans who had upset the social norms were asked to leave (Acts 16:38). And the authorities made the brilliant assumption that the social upheaval would of course subside.
All these highly complex social consequences were governed by models that ordinary people understood exactly. We can only guess what was happening in Paul's letter to one Christian slave owner. Here is a possible scenario.
-Onysimos- Useful had been Philemon's somewhat unprofitable slave. In his letter Paul admits Philemon had found him -ton pote soi achryston- the one who was previously a dead loss to you (Philemon 10). As a slave Useful had decided it was worth making a run for it. There was a risk, but his owner had become a Christian and might be more merciful than others. While Paul was imprisoned in his own hired house in Rome (Acts 28:3, or somewhere else), Useful became useful to Paul as a domestic servant (Philemon 11). After he was converted and baptized Paul discovered his status. It was a serious crime to harbor a runaway slave, and Useful's life was doubly in danger as a Christian and a criminal. After much prayer the Holy Spirit gave Paul the wisdom to solve the problem.
Paul sent the slave back to his owner with a letter, which God carefully arranged to have preserved for us. There was certainly a risk that Philemon could refuse Paul's tender appeal, have the slave mercilessly beaten, and himself commit apostasy from the Christian community. Since the letter was preserved I assume that Useful must have been baptized and welcomed to Philemon's assembly. We don't know whether Onesimus continued as a slave or as a servant, but he would certainly be doing much more useful work than before (Philemon 11).
The happy ever after Christian novel ending would be that Philemon freed Onesimus to remain working for him or leave as he chose. Philemon was a Roman citizen by cash payment, and he loved Onesimus so much that he viewed him as his own son. So he paid to buy him a Roman citizenship and got Useful to marry his daughter. Useful eventually became a Bishop, as did others who had previously been slaves. That is one of a hundred corny plots for a novel.
Whatever happened in the real life story of Useful, the fact is that
all over the Roman world people were astonished to see variations on this
plot being worked out before their very eyes. Eventually slavery in the
Roman Empire withered away. But the same outworkings of complex model theology
have been made visible in every country of the world. And right now in
the Sudan thousands of Christians are being killed, enslaved, freed, converted
every day at great cost in the fiercest persecution the Church has ever
known. And so the Church grows.