Only the deliberately blind could possibly miss what concerns Paul. Just as he rhetorically compounds the basis of his appeal, so here at least three times he repeats: be like-minded; have the same love; be one in spirit and of one mind. But how he gets there is a bit surprising, although by now certainly not unexpected. On the basis of your own—and our common—experience of the trinitarian God and of your well-known tenderness and compassion, then make my joy complete by getting your corporate life together. Again, this reflects the three-way bond between him, them and Christ that holds the entire letter together. Their unity in the Spirit, based on Christ's comfort, will bring Paul's joy over the advance of the gospel, already noted in 1:18, to full fruition. What is probably in view is his eschatological joy at their being together with him at the day of Christ (2:16).
The key word in the appeal, and indeed a key word in the letter, is the verb phroneo (see on 1:7), which is repeated in the first and third instances and has to do with the set of one's mind, how one is overall disposed toward something (cf. Rom 8:5-7)—thus (literally) "set your minds on the same thing"/"setting your minds on the one thing." This is the word that is picked up again in Philippians 2:5 ("have this same mindset, as Christ did") and in 4:2, where he reproduces the identical language of this first phrase in urging Euodia and Syntyche to the same mindset. The second occurrence (third phrase) is accompanied by the adjective sympsychos ( "together in soul"), thus joining mind and soul together, while picking up the phrase "one soul" from 1:27.
The middle phrase, having the same love, points back to the second clause in verse 1, "if any solace from [God's] love." The context suggests that Paul is first of all urging them to have the same love for one another that they already have experienced in God's love for them—and in theirs and his for each other. In 1:9 Paul told them he prays that their love might "abound more and more." Love, therefore, is not lacking in this community. At issue is the danger of its being eroded by internal friction. Thus they will fill Paul's joy to the full as they return to full and complete love for one another, which by definition means to care for another for her or his own sake. As someone well said: "Love begins when someone else's needs are more important than my own," which is precisely what Paul will urge in the elaboration that follows.
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