In this section of the letter, Paul shifts from his encouragement to serve one another humbly in order to be unified against an unspecified persecution to a second major issue, a potential attack by people from inside the church. Since the Philippian church was a tiny, diverse community of Christ followers in an otherwise pagan/Roman city, it is likely they faced pressure to participate in civic activities dedicated to various gods. This pressure may have come from families or civil authorities who would interpret the Christian refusal to participate in these events as scandalous and shameful.
The Jewish community, however, was already established and well-known for their legal permission not to participate in events violating their religious convictions. Lynn Cohick suggests, therefore, some early Christians sought the legal sanction of the synagogue as a way to avoid participation in these events (Philippians, 163). This is likely the the situation behind the the book of Hebrews (perhaps the opposite is true in Corinth). It is not completely clear the Philippian church was doing this, but there may have been an attraction to the synagogue as a place of worship and to Judaism as an old, established religion as opposed to the new, innovative Christianity meeting in homes with no sacrifice or priesthood, etc.
Paul’s description of his opponents is harsh by modern standards, but not unlike the type of rhetoric one would expect in the Greco-Roman world. To call someone a dog was a particularly vivid insult. Dogs were scavengers in the ancient world, something you might drive away with a stick: 1 Sam 17:23, Goliath says “am I a dog that you come to me with a stick?” In 1 Kings 14:11 dogs will scavenge the destroyed city of Samaria. From a Jewish perspective, a “dog” was an unclean Gentile. In 2 Kings 8:1 the Gentile Hazael calls himself a dog to demonstrate his humility, for example.
“Evil doers” is a generic way to describe an opponent. If the opponents are the same as Galatians, then they are probably not “evil” in the sense of worshiping false gods and indulging in sinful practices. Like 2 Cor 11:31 (where a similar phrase is used), they appear to have wrong theological presuppositions which lead to practice Paul cannot condone. Perhaps Paul is alluding to Psalm 22:16 in this verse. In the Septuagint, Psalm 22:17 uses the noun κύων (dog) as well as a participle of πονηρεύομαι, evildoers. Paul uses a phrase that means essentially the same thing (τοὺς κακοὺς ἐργάτας). This Psalm was understood as referring to the crucifixion very early in Christian preaching, so it is possible Paul wants to keep the cross at the center of this section of the letter. Just as Jesus was crucified by dogs and evildoers, these opponents have the potential to be just as dangerous.
“Mutilators” of the flesh obviously refers to circumcision. Paul uses an unusual word (κατατομή) because it sounds like the Greek word for circumcision (περιτομή). Paul may have in mind the principle in the Law barring people who have been mutilated from participating in worship. In the Septuagint, Leviticus 21:15 the cognate verb appears in list of types of cuttings (shaved head) or mutilations (carved flesh) resulting in defilement. Since a person who had been mutilated in some way was barred from worship at the Temple, Paul is describing these opponents as people who cannot approach God in worship. They are not just Gentile dogs; they are mutilated Gentile dogs who are unable to approach God!
Paul’s point in raising the issue of the opponents is to give a counter-example to the unity and humility of Jesus, Paul, Timothy and Epaphroditus. It is possible the Philippian Church is not directly threatened by same opponents of Paul as Galatians, but (ongoing) conflict with them would have been known to the church. The opponents have confidence in the flesh rather than in Christ. They are destroying the unity of the church by not seeking to have the same mind as Jesus. In fact, they may very well have the “same mind” as the dogs and evildoers who crucified the Lord!
Paul’s polemic against the “dogs” is remarkable because it is aimed at an opponent presenting itself as the correct (perhaps only) interpretation of what Jesus’ death on the cross means for Gentiles in the present age. The opponents are not evil pagan outsiders, but rather righteous insiders. There is a strong warning here to beware those within the church who appear to be righteous, but have intentions which hinder the Gospel.