Philemon can be a challenge from the perspective of preaching.
It has no central Christological themes and its primary issue--the status of a slave--can seem out of tune with contemporary concerns. What I find fascinating about the letter, however, is the messiness of the situation it describes. It looks a lot like life as I know it. I approach the letter, then, as a kind of case study on moving towards change.
Establishing the Context
Paul writes to Philemon in order to issue an appeal on behalf of Onesimus. In verses 15-16 Paul writes that Onesimus has been separated from Philemon "for a while so that you might have him back forever, no longer as a slave but . . . a beloved brother." How did Onesimus come to be separated from Philemon? Some have proposed that he was sent by Philemon to serve Paul while he was in prison. A parallel situation is described in Paul's letter to the Philippians where we learn that the Philippians have sent Epaphroditus to Paul in his imprisonment (Philippians 2:25-30). Others point to verse 18 as an indication that Onesimus is a fugitive slave who has perhaps stolen from Philemon ("If he has wronged you in any way, or owes you anything..."). The precise details elude us, but Paul's rhetoric indicates that he is attempting to re-negotiate the relationship between two individuals of unequal social status yet who are bound together in the ministry of Christ.
Relationships are messy. And, so often, it all depends on point of view. From Philemon's perspective Onesimus is a slave, and, as a slave, he has been useless (verse 11). What Onesimus actually was, we do not know. We never hear his voice nor are we told what he thinks or feels. We only hear just enough to suggest that he is estranged from Philemon. Because he is a slave, Philemon can do pretty much anything he wants to with respect to Onesimus. From a legal stand-point, it is his right.
Paul's perspective is different. He tells Philemon that this useless slave has, during Paul's imprisonment, become like a child to him. The only other person about whom Paul speaks in this way is Timothy (1 Corinthians 4:17; Philippians 2:22). Paul goes on to describe Onesimus as "my own heart." The depth of their relationship is indicated, on the one hand, by Paul's willingness to assume as his own responsibility any wrong that Onesimus has done towards Philemon (verses 18-19), and, on the other hand, by Paul's caution to Philemon that, if he considers Paul his partner, he should welcome Onesimus as if he were welcoming Paul himself. What this means for Philemon is that he cannot "see" Onesimus without seeing Paul, nor "see" Paul without seeing Onesimus.
This creates a stress point in the relationship between Paul and Philemon. Paul has called Philemon his "dear friend and co-worker." The word translated as 'dear friend' is agapētos ("beloved"), a word Paul also uses to describe Timothy (1 Corinthians 4:17). Therefore, just as Onesimus is dear to Paul, so is Philemon. Although Paul is bold enough in Christ to command Philemon to do his duty (verse 8)--i.e. to welcome Onesimus as his brother--he is unwilling to act in the matter of Onesimus without Philemon's consent (verse 14). This language could be passed off as a rhetorical strategy to gain Philemon's good will, but it may also reflect the very delicate path that Paul must tread.
Although Philemon will act of his own volition, he will not act in isolation. There are Apphia and Archippus, to whom the letter is also addressed, not to mention the church that is lodged in the house they share with Philemon. They are watching to see what Philemon will do. And there is Paul, who expresses his intent to visit Philemon when he is released from prison. Finally, there is Onesimus, whom Paul intends to send back to Philemon. He is probably wondering more than anyone what course Philemon will pursue.
Bound Together in Christ
Although the letter to Philemon contains no major Christological images, it is nonetheless grounded in an understanding that we live in and for Christ. It is "in Christ" that Paul commands Philemon to "do his duty" so that Paul's heart (perhaps a play on verse 12 where Paul refers to Onesimus as "my own heart") might be refreshed. This language of "in Christ" is a reminder that it is by the spirit of Christ that we live and are brought into a relationship of kinship with one another. It is because of this kinship relationship that Paul can dare to "command" Philemon, challenging him as a brother. Philemon is praised for his faith--that is, trust in and loyalty towards--the Lord Jesus. "Lord" can also be translated as "Master", a word that is used (significantly) only in reference to Jesus in the letter. Yet, Paul urges Philemon to make that faith effective by perceiving the good thing still to be done for Christ, whose spirit binds them together.
The letter to Philemon challenges us to discern, in and for Christ, what is the right thing to do. It would be easy if doing the right thing was, for example, taking out the garbage, or helping an elderly person cross the street. It is another when the right thing involves a radical transformation of social relationships: of learning to see people that time and experience have led us to view one way in a completely new way. It is another thing when this radical transformation of social relationships asks us to give up what we have come to view as our rights: to willingly let go of privilege. It is another thing when this letting go of privilege leads us to assume a relationship of kinship--of obligation--with those whom we have formerly viewed with suspicion because we now recognize that we are bound together in Christ.