The assumption is on your part. You read the verses and say, yup, Paul is speaking as an unbeliever. I read the verses, and, using careful analysis of the context and the grammar, say, Paul is speaking as a believer. You hang your opinion on the questions you are posing below because the appear in the passage. You have some key phrases that you zero in on all the time when discussing your view of the sinlessness of the believer and draw unwarranted conclusions when you encounter these phrases elsewhere.
You ignore that Chapters 7 and 8 are written as a unified whole for mature Christians, but with different perspectives of Christian life.
You have ignored my
comments showing the clear change of tense between Romans 7:7-13 and Romans 7:14-25. Verses 7-13 are clearly describing how Paul was led to Christ by the law. But something changes beginning in verse 14. It cannot be just more of the same from verses 7-13. The two sections are clearly demarcated by discussion of the value of the law (v. 7-13), how the law aids in Paul's salvation, and the believer's ongoing conflict with the law (v. 14-25) as they struggle with sanctification.
You assume based on appearances of "captive to the law of sin" (v. 23), "of the flesh" (v. 14), and "wretched man" (v. 24), that Romans 7:14-25 describes an unbeliever. But you ignore that the very same passage you claim Paul to be speaking as an unbeliever contains statements that
only a believer could possibly make: Paul desires to obey God’s law, hates sin (v. 15, 19, 21); humility and knows there is nothing good in his flesh (v. 17, 20-22), serves Christ with his mind (v.25).
As I noted previously, in verses
7-13, Paul is referring to his past experience of realization of sin through the law. In verses
14-25, Paul is referring to his ongoing struggle with what the law continues to reveal to him.
You won't accept the interpretation because you hold that the saved cannot sin. So, when you read these verses where Paul describes his ongoing struggle with sin and pursuit of sanctification you won't see it.
The key to grasping Paul's perspective is the ability to hold in tension seemingly conflicting points of view
in the present eschatological age in which we are living. What is true
positionally for the believer is not always true
practically in the believer's experience. Seemingly, if we are no longer slaves to sin, we would never sin again and perfectionism would be achieved.
But, whenever we see Paul chastising sinning believers such as the Corinthians or the Galatians, we never see him accusing them of not being Christians.
Yes, Paul called them childish, immature, weak, but not the unregenerate. Paul clearly understood the tension between positional truth and practical expression. So in his own life Paul could wail about the intense realization and of the pull of sin and its continual assault on the members of the body and its use of the law to provoke him to sin, while at the same time Paul confesses that "I delight in the law of God, in my inner being" (v. 22).
No unbeliever delights in God's law, for as Paul writes, unbelievers view God's truth as foolishness, not a source of delight (1 Corinthians 1:18-27; 1 Corinthians 2:14).