The NIV and other translations, following the unfortunate chapter division at this point, obscure the clear relationship of this paragraph with what has immediately preceded. Paul's sentence begins with a "therefore" ( "for this reason"), which is probably intended to pick up on all of 1:27-30. Thus although he is primarily resuming the appeal to unity, he does so now in light of the Philippians' suffering, in a struggle they have in common with Paul. "Therefore," he says in light of that—and to return to the matter at hand—"if there be any comfort in Christ, as indeed there is, . . . then complete my joy."
So how does one entreat friends to get back on track? By appealing to relationships, both divine and human. It may not always work, but this is certainly the primary way. Paul begins by appealing to the encouragement or "comfort" that being in (NIV united with) Christ can bring, as a direct response to their common experience of suffering for Christ in the preceding clause (1:29-30). But right at that point, before dictating a "then" clause, he adds three more "if" clauses, whose studied accumulation is part of the rhetorical effect.
The second clause, "if any solace of love," on its own is perfectly ambiguous. Does it refer to Christ's love (as NIV), or to Paul's and their shared love, or to God's love? While all of these can be shown to fit in context, most likely it refers to God's love for them, placed as it is between clear references to Christ and the Spirit, similar to the trinitarian grace in 2 Corinthians 13:14 (and with the same language).
While fellowship with is common coinage for the word koinonia in the third clause, it is doubtful whether it ever means precisely that. The word has to do with "sharing in" or "participating in" something (usually with someone else), which is almost certainly what is intended here (see 1:5). Paul's appeal is to their common sharing in the Spirit, thus picking up the language of 1:27.Finally, he appeals, if any tenderness and compassion. This phrase brings into sharp focus the basic ambiguities of these clauses, in terms of the direction of the relationships implied. Is it God's love toward them (i.e., on the basis of the prior work of grace from their experience of the Trinity) that Paul appeals to, or the Philippians' common life in Christ that they have experienced together heretofore, or the relationship that they and Paul have together in the gracious work of God? While commentators tend to line up fairly evenly among the three options, my guess is that what Paul does is not quite as tidy as we would have it. Most likely the three-way bond between Christ, the Philippians and Paul that is central to this letter is once more in view.
At the beginning the focus is clearly on Christ—and the comfort that is theirs (the Philippians) by being in Christ. But as what immediately precedes (v. 30) makes clear, and the "therefore" implies, Christ's comfort is shared by him and them together. As Paul moves to the next two clauses, the primary focus again seems to be on the Philippians' experience of (presumably God's) love and their sharing in the Spirit; but again, he and they share these as well. When he reaches the fourth clause, however, which noticeably lacks a modifier, the direction shifts toward their relationship with him, thus leading directly to the imperative make my joy complete. While it is true that tenderness and compassion are regularly attributed to God, in Colossians 3:12, a letter written in close proximity to this one, the two words appear together to form the phrase "bowels of mercy" ( "heart of compassion," which the NIV reduces simply to "compassion") as an especially appropriate virtue for Christian community. Most likely it is to the Philippians' own "heart of compassion" toward him that Paul finally appeals.
Thus the basis of the appeal is first of all the Philippians' own relationship to the triune God, which he and they share together, and second, his and their relationship to each other, brought about by their common relationship to the Trinity.
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