It is remarkable that the issue of Paul’s citizenship first arises in Philippi in Acts 16. Citizenship was not common in the first century, not everyone was guaranteed the privilege of being a citizen of the Empire. In 28 B.C. there were approximately 4.9 million citizens, by the time of Claudius there were 5.9 million. Most of these lived in Italy or were serving in the army. That Paul was a Roman citizen was significant, but even more so in the city of Philippi.
The city of Philippi was a re-founded as a Roman colony in 42 B.C. after supporting Octavian in the Roman civil wars. Rome settled a number of retired soldiers there in 42 B. C. and again after the battle of Actium in 31 B.C. As Polhill observes, the city was an impressive Roman city when Paul visited it (P&HL, 161).
One of the most striking features of the city of Philippi was civic pride. Joe Hellerman summarizes this “the Romanness of Philippi,” citing the catalog of inscriptions now available to scholars. He comments that compared to other cities in the Greek world, Philippi had a “preoccupation with honorific titles and offices which characterized the social priorities of both elite and non-elite persons in the colony.” Titles mattered to this colony of retired soldiers, since titles were a sign of social significance. To be a citizen of Rome was to have a higher social standing than the non-citizen.
Paul’s use of citizenship terminology in the letter suggests “that Paul sought intentionally to mimic the honor inscriptions that confronted his readers on a daily basis throughout the colony” (Hellerman, 783). In fact, Paul uses citizenship as a metaphor only in Philippians. In 3:20 he describes the believer as a “citizen of heaven” (πολίτευμα). In 1:27 Paul states that one’s “way of life” ought to be worth of the Gospel. The word translated “way of life” is πολιτεύομαι, to “be a citizen” (BDAG).
Paul’s point in using this language in Philippians is to show his readers that being “in Christ” is far superior to being “in Rome.” You may be a citizen of Rome, but that does not matter at all if you are a “citizen of Heaven.” I imagine that someone in Philippi might have judged a person who was merely a “citizen of Philippi” as socially inferior. The members of the church, according to Acts 16, included a business woman (Lydia), a retired soldier (the jailer) and perhaps a slave girl (formerly possessed). That “mix” of social strata is radical in the world of first century Philippi, yet Paul describes them as all citizens of a kingdom far superior to Rome.
If this reading of the citizenship metaphor is correct, then it will change the way we read Paul’s boasting in chapter 3, but also how we read the “Christ Hymn” in 2:5-11.
Bibliography: Joseph H. Hellerman, “Μορφη Θεου As A Signifier Of Social Status In Philippians 2:6,” JETS 52 (2009), 778-797. This article draws out the implications in the Christ Hymn in detail.