The “old nature”, the “old man”: one who lets himself be led by disorderly passions (cf. Rom 7:8), who lets his body do evil in the service of sin (v. 5; cf. Rom 6:12f). With the help of grace the old nature is being more and more broken down, while the new nature is constantly being renewed (cf. 2 Cor 6:16). Impurity and the other vices need to be uprooted so as to make room for goodness and its train of Christian virtues (vv. 12–13), especially charity (v. 14), which are features of the new nature.