So you think enslavement of humans is a superficial thing,
Only in comparison to enslavement to Satan and his kingdom, was the slavery comparatively less serious.
He needs freeing within and without.
Paul as an apostle is out to release men from slavery to Satan's kingdom.
He was occupied with Onesimus and Philemon both being deeply freed into the kingdom of Christ.
1.) Philemon, he addresses as "our beloved and fellow worker"
This means he approaches him not mainly as a secular man or employer or slave master. Rather he is to Paul a fellow - co-worker of the apostles of God.
By addressing Philemon this way he REMINDS Philemon of God's priorities. The chief matter here is not Philemon's worldly economic benefits. What is at stake here is not Philemon's material prosperity but his service to the Lord Jesus Christ.
Verse 1 is a callibrating of the slave master to his truer occupation - not just looking out for his wordly bank account but his standing with the fellow servants of God and Christ Himself -
"Paul, a prisoner of Christ Jesus, and Timothy the brother, to Philemon our beloved and fellow worker ..."
2.) Further Paul reminds the slave master Christian of his reputation, not as a rich land owner with servants, but of his Christian love to "ALL the saints"
"Hearing of your love and the faith which you have toward the Lord Jesus and to all the saints ..." (v.5)
IE. "Philemon, I hear that your faith in Christ and love toward ALL the Christian brothers and sisters is of note. This is a noble and righteous reputation you have among the believers."
The Apostle is callibrating Philemon's attention to his reputation among the disciples and apostles. It is not his worldly renown as a slave owning rich person which is important. His standing towards the Christian churches is what is important.
3.) In the past the believers have been encouraged and refreshed in their spirit through Philemon's upright Christian living. The implication is that Paul hopes he will not NOW let them down. He expects Philemon will not revert to a selfish money grubbing, grumbling oppressive slave master, incensed at his economic misfortune at losing a slave.
"For I had much joy and encouragement over your love, because the inward parts of the saints have been refreshed through you, brother." (v.7)
Paul continues his laser surgery on this case:
4.) Paul reminds Philemon that he [Paul] does have the position to CHARGE him with authority to do something. (As long as he is a co-worker) Paul has the position to DIRECT the man what he should do. But he would not. Rather than stand on his spiritual authority as a parent like aged apostle over Philemon, he would "entreat"
"Therefore though I have much boldness in Christ to charge you what is fitting, Because of love I rather entreat, being such a one as Paul the aged and now also a prisoner of Christ Jesus." (v.9)
Many of you reading will take this verse for granted. Here is a man who has risked his life for your spiritual benefit. He is a prisoner in a Roman prison. WHY? Because of his risking his life for your spiritual well-being.
Paul reminds Philemon that Philemon owes him his life!
"I, Paul, have written with my own hand: I will repay; not to say to you that you owe me even your own self besides." (v.19)
Pauls gospel preaching may have saved Philemon from alchoholism or suicide or depression or a tragically failed marriage, or worse. We do not know. But we can assume that this slave master experienced tremendous personal blessing from knowing the apostle. And that to the point that Paul could remind him that he [Philemon] owed his life to Paul's ministry.
Paul knows that Philemon has been very blessed in every way from knowing Paul personally. He has been a caring spiritual parent of Philemon. Yet he would entreat him and not authoritatively charge him.
Paul entreats the slave master and says in essence - Treat this man as you would treat me. If he owes you anything, charge it to ME.
"If he has wronged you in anything or owes [anything], charge that to my account. I, Paul, have written with my own hand: I will repay; not to say that you owe me even your own self besides." (v.19)
More on Paul's laser surgery of this tough slave / slave master / Christian brother case below.