For Paul, there are only 2 different mind-sets, only 2 different thought patterns=they are opposites. Your mind is either controlled by the Spirit or the sinful nature. Remember Paul is talking to Christians, who have the Holy Spirit. He makes it very clear in Romans 8:9 that if you don’t have the Spirit, you’re not yet a Christian.
"You, however, are controlled not by the sinful nature but by the Spirit, if the Spirit of God lives in you. And if anyone does not have the Spirit of Christ, he does not belong to Christ."
Romans 8:9
"For when we were controlled by the sinful nature, the sinful passions aroused by the law were at work in our bodies, so that we bore fruit for death." Romans 7:5
http://bible.org/seriespage/lesson-5-romans-8
http://bible.org/seriespage/lesson-5-romans-8
I remember learning in university about the philosophy of determinism which says we have no control over what we do. There is no free choice. We are led by our genetics, upbringing and circumstances. I could see the logic in that when it was explained and realized that the only free choice we have is whether we will follow God or not. If not, then Satan and evil control us. If we follow God, then He will control us.
This is an awesome truth. Those without God believe they control themselves, but they are wrong. It is frightening to think how many follow Satan all the way to the grave. It is so sad. If they only knew what a life with God is like they would run to Him.