During his ministry Jesus frequently appealed to the sorts of starkly different pathways that are set before humanity. There is the broad way that leads to destruction and the narrow way that leads to life. There are two different foundations upon which to build. The foolish builder chooses the sand while the wise builder chooses the rock. Following this pattern, Paul sets before us two ways to live. Either we will live according to the flesh or according to the Spirit.
But these two ways are not equally available options for everyone without distinction. In other words, Paul is not suggesting that Christians may live either according to the Spirit or the flesh. Nor is he suggesting that unbelievers have the same menu of options before them. What Paul is telling us is that it is not possible for the unregenerate to walk according to the Spirit for the Spirit does not dwell in them. Accordingly, they have neither the desire nor the ability to walk in a way that is pleasing to God (vv. 7-8). On the other hand, Christians, “are not in the flesh but in the Spirit” (vs. 9). This is not to say that Christians do not still battle against sin. But that’s the point. They no longer live according to the flesh. Christians are at enmity with sin precisely because of the indwelling Holy Spirit.
In this life we will either be servants of the flesh or servants of Christ for we will be enslaved by one or the other. For Christians – those “who live according to the Spirit,” – a life of joyful obedience is less imposed from without than generated from within by the Holy Spirit. As Schreiner observes, “Verses 5-11 do not constitute an exhortation to live according to the Spirit or to fulfill the law. Rather, they describe what is necessarily the case for the one who has the Spirit or is still in the flesh…Obedience is rooted in the transforming work of the Spirit, and thus is not a burden imposed from without but a delight embraced from within” (p. 409).