“The second reality that Paul engages is the assembly (Greek ekklesia) of the Greco-Roman city (Greek polis). The ekklesia was something like the city council, a group of male elders who met to deliberate about local issues and to ensure that the polis was faithful to its heritage and values. The ekklessia had the additional duty–especially if the polis happened to be a Roman colony and/or home to the imperial cult (e.g., Corinth, Philippi, Thessalonica, Ephesus)–of dutifully and creatively expressing its loyalty to Rome and to its lord and savior, the reigning emperor.
Paul uses the term ekklesia for “the church” as a term of both continuity and discontinuity. On the one hand, it designates the assembly of believers who affirm Jesus as Lord and constitute the renewed “Israel of God” (Gal 6:16). On the other hand, this assembly exists as an alternative ekklesia and even an alternative polis, since it incorporates not just a few leaders but an entire believing community. It exists as a counterculture to embody the values of its true savior and lord, Jesus the crucified and resurrected Messiah.
The church, therefore, is a visible, even a “political” reality rather than just a group with invisible “spiritual” bonds, whose mission it is to be a living commentary on the gospel it professes, the story of the Lord (Jesus) in whom the church exists and who lives within the assembly. (See especially Phil 2:1-15.) As such, the church reflects the character of the God revealed in Christ. This countercultural community is not produced by human effort, nor does it occur to perfection overnight; it is a process of divine activity and communal and personal transformation (e.g., Rom 12:1-2; I Thess 3:11-13; 5:23-28). To be holy is to be different, different from those outside the church and different from the way we used to be, changed from what was “then” to what is “now” (Gal 4:8-9; I Cor 6:9-11; Eph 2:1-6; Col 3:1-7).” (Michael J. Gorman, Reading Paul, pp. 133-134)