The answer is: His life

v19 - Paul mentions it, but is saying that he doesn't need to go into the details. Presumably Paul is talking about converting Philemon to a believer in Christ, rather than a literal saving of his life.

The book of Philemon gives us a unique glimpse into the early Christian community and the personal relationships that shaped it. When Paul discusses what Philemon “owes” him, he’s really highlighting the transformative power of faith. Paul acts as a mentor, guiding Philemon from a life perhaps marked by different priorities to one focused on love and service—a foundational theme of Christian living.

Saying Philemon owes his life means a shift in identity, akin to how a caterpillar transforms into a butterfly. It emphasizes that Paul not only influenced Philemon’s spiritual journey but also sought to define the essence of their relationship in terms of discipleship rather than mere obligation. This adds a layer of warmth to their connection.

Here's a fun historical echo: Philemon might have been part of a house church, which were crucial to early Christianity’s growth as these smaller, intimate gatherings fostered community and allowed for personalized teachings. Imagine meeting in your living room for spiritual discussions—this was the heartbeat of early Christian community life!

Also noteworthy is Philemon’s example in bearing the luggage of reconciliation, as he is encouraged to accept back his runaway slave, Onesimus. This sentiment echoes throughout scripture, reminding us of the call to embrace forgiveness, whether toward friends, family, or even societal divides. The theme of personal relationships is a central thread that runs through many letters of the New Testament, encouraging interdependence in faith-conducive communities.