A former slave, fearing his ex-master’s anger, seeks out a powerful ally who might plead on his behalf. The story of Philemon? Actually, it is also the story of Sabinianus, whose freed slave came for help to the Roman senator Pliny. As N. T. Wright explains (as summarized by Chaplain Mike at InternetMonk), the similarities between the story of Sabinianus and the biblical account of Philemon offer an important study in contrasts:

But the main impression, once we study the two letters side by side, is that they breathe a different air. They are a world apart. Indeed — and this is part of the point of beginning the present book at this somewhat unlikely spot — this letter, the shortest of all Paul’s writings that we possess, gives us a clear sharp little window onto a phenomenon that demands a historical explanation, which in turn, as we shall see, demands a theological explanation. It is stretching the point only a little to suggest that, if we had no other first-century evidence for the movement that came to be called Christianity, this letter ought to make us think: Something is going on here. Something is different. People don’t say this sort of thing. This isn’t how the world works. A new way of life is being attempted — by no means entirely discontinuous with what was there already, but looking at things in a new way, trying out a new path.

Chaplain Mike summarizes:

Pliny was concerned about resolving a problem in a way that maintained social order. Said social order was based on social distinctions and rules of propriety, as well as the rewards and punishments that kept it intact. Second chances were allowed up to a point; kindness and mercy had room to operate within limits. In the end, Pliny remained on top, Sabinianus was beholden to him, and the freedman was on the bottom of the pile.

Paul was concerned about two entirely different matters: reconciliation and unity in the Messiah. Paul was in prison because he advanced this agenda. From there he continued to promote these concerns to people like Philemon, by not only writing about them but also by offering to be the very bridge by which two parties at odds could become one again.

For Paul it was all about Jesus the Messiah, and this is what Jesus was all about.