<p>1:13 <i>I would have been glad to keep him with me, in</i> <i>order that he might serve me on your behalf during my imprisonment for the gospel- </i>If Onesimus returned to Rome and served Paul there, he would be ministering to Paul as if Philemon was doing this- &ldquo;on your behalf&quot;. So as Paul was represented by Onesimus (:12,17), so likewise Onesimus would represent Philemon. This is the John 17-style unity which there is in Christ. It would seem that if Onesimus could be so useful to Paul in Rome, he was not therefore in prison; therefore Paul's outreach from within prison had reached to a runaway slave outside prison. And of course Onesimus was free to travel back from Rome to Philemon. Maybe Paul's teaching about grace in the letter to the church at Rome had been heard by Onesimus, and so he had come to ask Paul about working it all out in practice.</p>