Each and every one of us carries the proof of Adams fall, within and throughout the very fabric of our physical bodies. That is where the sin nature resides.
The sin nature does not reside in the soul, because upon death, the soul and spirit leave the body and go face-to-face with the Lord in heaven. Sin does not travel with the soul into heaven, but remains behind to decay with the physical body.
Thus with this repetition of instruction from Paul, we see the inner conflict within ourselves, between sin on the one hand, and good on the other hand. The determining factor as to which wins out, resides in the soul, where the individual makes decisions one way or the other.
Sin is extremely powerful, and when combined with the influence of the evil policy that Satan has imposed, then imprisonment within these chains of slavery, is virtually impossible for an individual to escape on their own.
We know within our soul, what is good and right, and what we should do, but the forces within our body drive us to the things that we should not do. And that encompasses all manner of sin throughout the broad spectrum of sin, from the simplest of sins, to the most extreme evils imaginable.
In this world now we have the restraint of Bible doctrine, and the indwelling of the spirit, which serves as a governor over sin, limiting it and preventing it from its fullest potential.
Even with this restraint, history has witnessed, what we would call, extremes in the exercise of evil within humanity.
But when the rapture occurs, and all restraint is removed from the world, and sin and evil are literally turned loose, then society will become witness to, and victims of, evils that are beyond imagination.
The only defense and protection against sin and evil, is Bible doctrine in the soul. And you have to engage in a daily study of Bible doctrine in order to get into your soul.
Study [by instruction],
to show thyself approved [spiritually mature]
a workman [student]
that need not be ashamed [ignorant],
rightly dividing [learning, understanding, discerning]
the word of truth [Bible doctrine].