Addressing Philemon as well as the church that meets in Philemon's house, Paul makes this prayer: "I pray that the koinonia of your faith may become effective when you realize all the good that we may do for Christ" (vv. 4-6). What was Paul's intention in revealing the content of his prayer for Philemon in a letter he knew would be read publicly? Why was Philemon's koinonia of faith both a matter of praise and an object of concern for Paul? The text does not answer these questions until ten verses later. In verse 16, one finds this radical and earth-shaking request, namely that Philemon receive Onesimus no longer as a slave but more than a slave, a beloved brother in the flesh and in the Lord (v. 16). This book stems from the realization that the word "brother" in verse 16 not only explains why Philemon's koinonia of faith was ineffective (v. 6) but also strengthens my claim that a call to an ethic of koinonia is the central message of the letter.