NOTE: This is a condensed excerpt from my forthcoming (2014) commentary on Philippians.
Both the purpose and the result of the Philippians’ love abounding in knowledge and insight/discernment are stated here in verse 10. The purpose is so that you may approve what is excellent. Although the verb translated approve (dokimazō) can mean to put to the test or examine (e.g., 1 Cor 11:28; 2 Cor 13:5), here it has the sense of proving or approving something. Paul uses similar language in Romans 12:2—”Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern [dokimazein] what is the will of God, what is good and acceptable and perfect” (cp. Eph 5:10). As biblical love abounds more and more in knowledge and all discernment it enables believers to recognize, embrace and follow God’s good and acceptable and perfect will.
But rather than speaking of approving God’s will as he does in Romans 12:2, Paul instead speaks of what is excellent. Behind this expression is a verb (diapherō) that means to be worth more or superior to something. The specific expression used here (ta diapheronta) refers to those things that are significant/essential or even excellent. While some things are clearly right or wrong, good or bad, many things are not so clear cut. Indeed, it is especially difficult to distinguish between what is good and what is best, what is permissible from what is preferable. That is why Christian love must grow in knowledge and all discernment, so that God’s people can demonstrate through their lives their approval of what is excellent. “Here we have a definition of Christian wisdom—to know what is advantageous or expedient—not to torture the mind with empty subtleties and speculations.”
The result of approving the things that are excellent is so that you may be pure and blameless. The rare adjective translated pure (eilikrinēs) refers to something that is unmixed, a sense that was extended into the moral realm as being sincere, lacking hidden motives or pretense. The adjective translated blameless (aproskopos) is almost as rare; it can have the sense of either being without fault or not causing offense to someone else. While both senses fit here, the context points to the first sense. The combination of these two terms encompasses both internal dispositions and outward actions. The result of approving the things that are excellent is a life that is pure both inwardly and outwardly. The experience of the Christian makes it clear that no one is able to perfectly live out this high calling, and this is perhaps even implied by the fact that Paul is praying for this to be a reality for the Philippians. But over time there should be a gradual and noticeable growth in these areas the longer one walks with Christ.
 Cf. BDAG 2.b. In the NT it is a distinctly Pauline word; 17 of the 22 occurrences are in his letters. His usage is roughly evenly split between the two senses of test/examine (1 Cor 3:13; 11:28; 1 Cor 13:5; Gal 6:4; 1 Thes 2:4 [2x]; 1 Tim 3:10) and prove/approve. The former sense is also prevalent in the Apostolic Fathers of the need to examine bishops and deacons (1 Clem 42:4; 44:2; Did 15:1), prophets, (Did 11:11; Hmk 1:7 [2x], 16) and travelling teachers (Did 12:1). In the LXX (36x) it is prevalent in the Wisdom literature in particular. In the Psalms it is used to speak of God trying/testing the godly (16:3; 25:2; 65:10; 80:8; 138:1, 23) as well as Israel testing God in the wilderness (94:9). The verb is also common in both Josephus (29x) and Philo (40x). An example of this verb used with the sense of approve is a marriage contract from before the NT period which requires disputes to be settled by three men “whom both shall approve” (P. Eleph 110 cited in VGNT). This verb was also a technical term for testing currency (e.g., Plato, Timaeus 65c); see Marvin Richardson Vincent, A Critical and Exegetical Commentary on the Epistles to the Philippians and to Philemon (ICC 37; New York: C. Scribner’s Sons, 1897), 12.
 Calvin et al., Philippians, 32.
 Cf. BDAG; LN. The only other NT occurrence is 2 Peter 3:1, where it describes the kind of thinking that should be characteristic of a believer. In the only LXX occurrence, wisdom is described as a pure emanation of the glory of God (Wis 7:25). Philo (25x) uses it in a variety of ways, mostly to modify a person’s mental faculties (e.g., Opi 1:8; Ebr 1:101, 190; HER 1:98, 308; Leg 1:88; Cng 1:143 [2x]; Spe 1:99; Mos 2:40; Pep 1:45; Qex 2:47). Some have argued that eilikrinēs comes from a combination of eilē (“warmth or light of the sun”) and krinō (“to judge”), with the resulting sense of “tested by sunlight”; see, e.g., TDNT 2:397-398; EDNT. But this origin is uncertain at best, and has been questioned by others; see, e.g., Vincent, Philippians, 13; J.H. Moulton and W.F. Howard, Accidence and Word-Formation (A Grammar of New Testament Greek vol. 2; Edinburgh: T. & T. Clark, 1908), 105; Kennedy, “Philippians,” 422.
 It occurs just two other places in the NT, either in reference to Paul’s conscience (Acts 24:16) or his behavior among both Jews and Greeks (1 Cor 10:32).
 “Paul’s central concern is not primarily the readers’ relationship to outsiders but the wider issue of how they will appear in the presence of the coming Lord” (Bockmuehl, Philippians, 68-69).
 There may even overtones from the purity required of priests serving in the temple; see N. T. Wright, The Prison Letters: Ephesians, Philippians, Colossians, and Philemon (2nd ed.; Paul for Everyone; Louisville: Westminster John Knox, 2004), 86.