6:14 7 For sin shall not have dominion over you: for ye are not under the law, but under grace.
(7) He grants that sin is not yet so dead in us that it is utterly extinct: but he promises victory to those that contend bravely, because we have the grace of God given to us which works so that the law is not now in us the power and instrument of sin.
Sin is not utterly extinct in us, but we can fight against it.
Why is sin not extinct? Why do we struggle against it? God grants us salvation, and grace washes away our sin, and we are baptized with Christ into newness of life… so why do we continue to sin?
This is, as is my particular bent, a philosophical question. It’s not quite the same as “If God is Good, then why does sin exist?” The question is “If God grants us salvation, why do we continue to sin?”
Paul says that the old self has died and we have a new spirit. But he also admits that he continues to do what he does not wish to do.
Here’s my answer: we continue to sin because that is the evidence that we continue to have free will. Even after I choose God, and grace fills my life, I can still freely choose to act against the will of God, and that is sin.