A mind set on the flesh is essentially hostile toward God. To set one"s mind on the flesh is contrary to God"s law. [source][source][source]
From the end of Romans 8:7 it seems clear that Paul was thinking of an unsaved person (cf. Romans 8:8-9). Evidently he wanted "to expose the flesh in its stark reality as being totally alien to God and his purpose." [1] What interests a person reveals his or her essential being. It is possible to walk according to the flesh ( Romans 8:4-5) and not to be in the flesh, however. In other words, it is possible to live as an unregenerate person even though one has experienced regeneration. [source][source][source]