Now that the basic matters are in hand--reporting on his own situation, appealing to the Philippians to get theirs in better order, and informing them as to what's next--Paul returns once more to their "affairs." But here both the way Paul begins and the content of the section have made it difficult for later readers to see how things fit together--a problem abetted by the variety of paragraphing options for verses 1-2 in our English translations.
Paul begins with what appears to be a concluding word (v. 1a); but this is followed by a sentence indicating that he is about to repeat things they have heard before (v. 1b), and then by a severe denunciation of some people (v. 2) who the following sentences (vv. 3-6) imply are Jewish Christian itinerants promoting the circumcision of Gentiles. After telling his own story in response (vv. 4-14) and encouraging the Philippians to follow his example in contrast to some who do not (vv. 15-21), he concludes (4:1-3) with language and ideas that recall the opening appeal in 1:27 and 2:2. This is then followed (4:4) with a repetition of the call to rejoice in the Lord with which the whole began.
Various hypotheses have been offered to explain how all this fits (or doesn't fit) in the letter: that an editor has "sewn together" two or more letters of Paul to the Philippians, or that Paul started to conclude his letter, was interrupted or put it aside for awhile, and then took off on a totally new tack before returning to his interrupted conclusion. But such views tend to focus on verses 2-6 in such a way as to neglect the remarkable verbal and conceptual ties the rest of this section has with what has preceded.
Indeed, the correspondences are so striking that it should cause us to read verses 2-4(6) as related in some way to the rest, even if we cannot be sure of that relationship. The correspondences include
Paul's description of his Christian life as one long yearning to gain/know Christ (vv. 7-10; cf. 1:21-23)
his description of "knowing Christ" (vv. 10-11) in terms that echo the heart of Christ's story (2:6-8), followed by his own confidence in attaining the eschatological prize (vv. 12-14) just as Christ's vindication followed his suffering and death (2:9-11)
his appeal (vv. 15-16) that the Philippians adopt his own mindset on these matters (life that is cruciform, while pressing on toward the sure future), the latter being a repeated motif in chapters 1--2
his second appeal (vv. 17-21) that they follow his example in contrast to some enemies of the cross whose minds are set on earthly things and thus will miss the final glory of heavenly citizenship (cf. 1:27; 2:2, 9-11)
his final appeal (4:1) that they thus stand firm (echoing 1:27)
which all concludes by a very specific appeal to two women leaders (4:2-3) in the precise language of the more general appeal in 2:2
These correspondences, in which Paul's own story echoes that of Christ and equally serves as an example of the mindset the Philippians are to pursue, are too many and too exact to allow all of this to be simply digressive. What this suggests further is (1) that to loipon in 3:1 (NIV finally) means "as for what remains to be said," thus introducing a concluding section of the letter (cf. 1 Thess 4:1; 2 Thess 3:1), not a conclusion per se; (2) that the appeal to "rejoice in the Lord" serves to frame the whole section, as the context in which the warning of verse 2 and the various repeated appeals are to be understood; (3) that the warning against the "Judaizers" in verses 1b-6 (9) should be understood as related in some way to the appeal to having Christ's mindset; which in turn (4) is most likely also related in some way to the friction between the two women that is responsible for much of the content of this letter.
How these are related to the whole is more speculative. Very likely one of these women was urging that the community go the way of the Judaizers--either because securing oneself with God by visible forms of religious observance has for some reason a very strong appeal even to Christian believers (cf. Galatians) or because Judaism, even though despised for its exclusive monotheism, had been given legal standing in the Empire, while the followers of the crucified Nazarene were becoming more and more suspect (see Tellbe 1994).
The key to how this section begins lies in the area of Greco-Roman friendship, where to be friends meant automatically to have enemies in common (see introduction). Pilate, for example, could not be "a friend of Caesar" and at the same time not consider Jesus as an enemy who was a potential threat to Caesar (Jn 19:12). The problem for Paul is all the more striking if one of his own friends (Euodia or Syntyche) in Philippi is leaning toward a view that is opprobrious to him.