Philemon was written by Paul to a friend, Philemon. Philemon evidently lived in or around the area of Colosse in Asia Minor (Modern day Turkey). Based on the ending of both the letter to Philemon (Philemon 23-25) and the ending of the letter to Colosse (Colossians 4:7-17) it appears both letters were written and delivered together. Paul was writing from prison in Rome waiting a trial for events that supposedly occurred in Jerusalem (See “Paul “sent one” to the Gentiles” and “The New Testament Dissection” for more information on Paul). Paul was I prison there from about 60-63 AD. According to Colossians 2:1 Paul did not personally found the church in Colosse. During his third journey around the Mediterranean he spent two years in the major city of Ephesus teaching people about Jesus. According to Acts 19:9-10 many people in the region heard about Jesus during this time. It was probably in Ephesus that Philemon heard and believed. He and others then returned to their homes telling their friends and families about Jesus. As people in these areas believed churches were formed. According to Colossians 1:7 that is what happened in Colosse were Epaphras told the people about Jesus.
Philemon is a very personally letter and some people wonder why it was made so public, even to the point of being included in the Bible. It was common in the early days of the church for churches to meet in the homes of members. It looks like that was the case with Philemon (Philemon 2). These people were usually quite wealthy. Most people in the cities of that day lived in small spaces, a room or few rooms, only the rich had home big enough for a church, even a small one, to meet in. As a leader in the church (and a rich guy) Philemon’s personal life would have been watched by many. Paul is writing to his friend because one of his slaves had run away. By some set of events which we do not know the slave, Onesimus, wound up in Rome (a long ways away) where he came across Paul. Paul told Onesimus about Jesus and Onesimus believed. At the time of writing the letter Paul also had visitors from the area around Colosse and it looks like at least Epaphras was in jail with Paul (well not actually in jail it was a house arrest). Back home everyone probably knew about Philemon’s run away slave. If they did not already know they soon would that he was with Paul in Rome. Paul had a situation that he needed to deal with both personal and public under the circumstances.
It is certainly providential (God created the situation) that Onesimus met up with Paul. Slavery is certainly one of the big moral issues of all time. At the time of Paul some scholars believe at least one third of the people in the Roman empire were slaves. Some people were captured in military conquests and forced into slavery. Others were made slaves to pay off debts they owed, while still others were slaves willingly, selling themselves to someone in exchange for care and support. Earlier in Roman history slaves were considered the property of their master and the master could do whatever they wanted to with the slave, including torture and execution. In 136-132 BC and again in 70-71 BC there were two major revols by slaves (they were in Eunus and Spartacus). In addition the Stoic philosophers were pushing for the equality of all human beings. These events affected the people of the Roman empire and by the time of Paul there had been many reforms and laws were put into place to give slaves at least some rights. Slaves were at least acknowledged as human beings. But slavery was also a big part of the workings of the empire and was not soon to be abandoned. Interestingly as a result of some of the reforms the situation of many slaves actually got worse. When slaves became old they were often “set free” but they had nowhere to go, no way to live, and they suffered. From the very beginning of the nation of Israel the Law of Moses demanded humane treatment of slaves. They were always considered human beings under that system and slaves who were Israelites had to be released on the Sabbath Year (every seventh year the nation of Israel was to release the slaves, forgive debts, and not work their fields.)
So what was Paul to do? He had written some 20 years earlier to the church in the region of Galatia that “in Christ there was neither Jew nor Greek, there is neither free man nor slave, there is neither male nor female, we are all one in Christ” (Galatians 3:28). Now that theory would be put to the test in the most person and public way. Philemon is the answer to what Paul would do.