With another complex sentence Paul comes back to the concern of 1:27—2:4. The complexity is created by his trying to cover a great deal of ground in a single sentence. His concern is that they "obey" now (cf. v. 8), just as they have always done. But before giving definition to obedience, he interrupts himself by placing the appeal within the "presence/absence" friendship motif (cf. 1:27). The content of the appeal is then expressed with a deliberate echo of "your salvation which is from God" (1:28). These echoes not only make the sentence complex, they also create some difficulty for English readers. The verb Paul uses means "to accomplish" or "to carry out," which is not easy to translate here without creating the impression that salvation is of our own doing. And to top it off, it is easy for us to read the imperative individualistically, rather than, as with verse 4, as a call to individually work out our common salvation in our life together.
The momentary "presence/absence" digression deliberately reminds them of the earlier appeal in 1:27. Along with the affectionate vocative (literally, "my beloved ones") and the reminder of their excellent history in this regard (as . . . always), this motif places the appeal to obedience within the context of their long-term friendship and common affection. But obedience to whom, Paul or God, since elsewhere Paul goes either way? In context it most likely means obedience to his earlier appeal in 1:27—2:4. But that automatically means obedience to Christ, the only kind of obedience to his own words that Paul could care anything about. In his view faith in Christ is ultimately expressed as obedience to Christ, not in the sense of following the rules but of being devoted completely to him. This appeal, after all, closely follows the twofold reminder of Christ's own obedience that led to the cross and of his present status as Lord of all.
Obedience in this case takes the form of work out your own salvation, meaning "in your relationships with one another live out the salvation Christ has brought you." This is therefore not a text dealing with individual salvation but an ethical text dealing with the outworking of salvation in the believing community for the sake of the world. That they must comply with this injunction at the individual level is assumed, and that their final salvation will be realized personally and individually is a truth that does not need stating, because that is not at issue here. The present concern is with their being God's people in Philippi, as 2:15 makes certain.
The phrase with fear and trembling indicates how important this matter is for Paul. One does not live out the gospel casually or lightly, especially in light of verses 6-11, but as those who know what it means to stand in awe of the living God. Nothing of cringing or lack of confidence is implied. Rather, the gospel is God's thing, and the God who has saved his people is an awesome God. Thus working out the salvation that God has given them should be done with a sense of "holy awe and wonder" before the God with whom they—and we—have to do.
By putting his appeal this way—urging the Philippians to work out your salvation with fear and trembling—Paul recognizes that he may have painted himself into something of a corner regarding his essential theology. So he immediately puts it in the context of God's action. For, he explains, God is the one who empowers you in this regard. They are indeed to "work at" it (katergazesthe); they are able to do so because God himself is "at work" (energon) in and among them. This does not mean that God is "doing it for them," but that God supplies the working power. Happily for us, God is on the side of his people. Not only does he have our concern at heart, but he actively works in our behalf for the sake of his own good pleasure. The rest of the sentence gives us the "where, what and why" of that empowering.
The "where" is in/among you. As in 1:6 and 2:5, when using this phrase in a corporate context Paul primarily means "among you." For that to happen it must begin in you, that is, in the resolve of each of them to see to it that God's purposes are accomplished in their community.
The "what" is loaded with theology. God empowers both our "doing" (energeo, the verb just used to describe God's "working") and the "willing" that lies behind the doing. Christian ethics has nothing to do with rules that regulate conduct. Rather, it begins with a mind that is transformed by the Spirit, so as not to be conformed to this age but to the character of God, knowing God's will, what is good and pleasing and perfect to him (Rom 12:1-2). We are not those who have been begrudgingly caught by God, so that we obey basically out of fear and trembling over what might happen if we were to do otherwise. Rather, being Christ's means to be converted in the true sense of that word, to have our lives invaded by God's Holy Spirit, who creates in us a new desire toward God that prompts godly behavior in the first place.
But Christian ethics lies not just in the "willing." In Romans 7:18, in his description of life before and outside of Christ looked at from the perspective of life in the Spirit, Paul described pre-Christian life with these same verbs. "To will," he said, was present with him; but without the Spirit, "carrying out [katergazesthai] the good" does not happen. As a believer, however, Paul will have none of that (i.e., of our not being able to carry out the good that we will). Hence he urges the Philippians to "work it out" precisely because God (by his Spirit) is present with us both to will and to act on the good God has prompted us to will.
The "why" (according to his good purpose, NIV) is ambiguous. The word eudokia (good purpose) occurred in 1:15 as the motivation for those who preach Christ out of love and "goodwill" toward Paul. In light of what is about to be urged (v. 14), that meaning could prevail here as well; that is, God is at work in them both to will and to do what promotes goodwill in the community. More likely, however, given the emphasis of the present sentence, Paul intends God's own eudokia—in which case this word probably leans toward "good pleasure," in the sense that God does this for his people because it pleases him so to do. In any case, the preposition hyper should bear its regular sense, "for the sake of." This does not mean that God, despite verse 6, is a self-gratifying being after all. Rather, all that God does he does for his pleasure; but since God is wholly good, what pleases him is not capricious but what is wholly good for those he loves. God's pleasure is pure love; it delights God to delight his people.
Thus with verse 13 Paul puts the imperative into theological perspective. What follows is to be understood as flowing directly out of this word; what pleases God in this instance, of course, is that the Philippians cease the in-fighting that is currently going on among some of them.