Is the biblical way of thinking about achievement better described as fruitfulness? In John 15:1–8, Jesus draws on his famous metaphor of the vine and branches. Jesus is the true vine, and the Father is the vineyard keeper (15:1). Unfruitful branches are removed and all fruit-bearing branches are pruned in order to produce more fruit (15:2). No branch is able to bear fruit unless it remains on the vine—unless it remains in Jesus (15:4). Nothing can be done apart from Jesus (15:5). Jesus’ Father is glorified by branches that bear much fruit and prove to be Jesus’ disciples (15:8).
There are two main themes here. First, Jesus’ disciples are expected to be fruitful. Second, this fruitfulness is only possible in union with Christ.
Dealing with the latter first, Jesus repeatedly uses “in” language: remain in me, and I in you (15:4); the one who remains in me and I in him (15:5); if anyone does not remain in me (15:6); if you remain in me and my words remain in you (15:7). Throughout John 14–17, Jesus draws on the theological concept of mutual indwelling. He is in the Father; the Father is in him. He will be in his disciples, and they will be in him. Mutual indwelling is one aspect of our union with Christ. It is a profoundly important spiritual connectedness with Christ.
Second, what does Jesus mean by fruitfulness? Commentators differ on this point. Does Jesus mean spiritual fruitfulness—growing in spiritual maturity, prayer, dependence upon God, evangelism, and so forth? In support of this is 15:8: Jesus’ Father is glorified by disciples’ fruit which proves them to be Jesus’ disciples. Fruitfulness cannot be reduced to achievement, but true fruitfulness includes disciple-achievement.Whatever fruitfulness is, it is a mark of discipleship. But is this narrow sense of fruitfulness really justified?
Certainly we must include those “spiritual” markers of discipleship as part of fruitfulness. But is Jesus not concerned with the whole life of his disciples? I think it is hard to limit Jesus’ concern only to prayer, evangelism and so forth. As D. A. Carson says, “This fruit is nothing less than the outcome of persevering dependence on the vine, driven by faith, embracing all the believer’s life and the product of his witness.” The fruit embraces all the believer’s life. If this is correct, we must conclude that fruitfulness at least includes the concept of achievement.
However, it is not correct to say that fruitfulness equals achievement, as though that’s all the fruitfulness is. That is just the opposite kind of reductionism as saying that fruitfulness only involves “spiritual” characteristics. If achievement were the only “fruit” observable in a believer’s life, surely this would fail the test of fruitfulness. Prayerful dependence on Jesus is required (15:7); keeping Jesus’ commands is required (15:10); love for others is required (15:12).
Also, it is not just any type of achievement that should be seen as fruitfulness. It is the kind of achievement that is accomplished by virtue of being in union with Christ. It is disciple-achievement that is required.
So, is achievement better described as fruitfulness? Yes and no. Yes, because disciple-achievement is a type of fruitfulness. No, because fruitfulness includes more than only achievement. Fruitfulness cannot be reduced to achievement, but true fruitfulness includes disciple-achievement.
 D. A. Carson, The Gospel According to John (Leicester: IVP, 1991), 517.