Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
In all that follows we have still the judgment of unbridled nature, of will in its different forms: contentions that arise from the lusts of the natural heart; request made to God proceeding from the same source; the desires of the flesh and of the mind developing themselves and finding their sphere in the friendship of the world, which is thus enmity against God. The nature of man covets enviously, is full of envy with regard to others. But God gives more grace: there is counteracting power, if one is content to be little and humble, to be as nothing in the world. The grace and favour of God are with such an one; for He resists the proud and gives grace to the humble. Upon this, the apostle unfolds the action of a soul directed by the Spirit of God, in the midst of the unbelieving and selfish multitude with whom it was associated. (Jam 4:6-10) For he still supposes the believers whom he addressed to be in connection with the law. If they spoke evil of their brother, to whom the law gave a place before God, they spoke evil of the law, [See Note #1] according to which his value was so great. Judgment belonged to God, who had given the law, and who would vindicate His own authority as well as grant deliverance and salvation.
Verses 13-16 (Jam 4:13-16). The same self-will and forgetfulness of God are blamed, the false confidence that flows from reckoning upon being able to do as one pleases the absence of dependence on God. Verse 17 (Jam 4:17) is a general conclusion, founded on the principle already suggested (Jam 3:1) , and on that which is said with regard to faith. The knowledge of good, without its practice, causes even the absence of the work which one could have performed to be a positive sin. The action of the new man is absent, that of the old man is present; for the good is before our eyes we know what we ought to do, and do not choose to do it; there is no inclination to do it we will not do it.
Note #1
Compare Th1 4:8 where the Spirit takes the place of the law here.