Paul in Romans 7:13-25 is pointing out two different dimensions being governed by two different sets of law. He is definite when speaking of the flesh vs. spirit as two separate operations, just like how Lord Jesus proclaimed in John 3 to Nicodemus.
Rom 7:13-25
13 Was then that which is good made death unto me? God forbid. But sin, that it might appear sin, working death in me by that which is good; that sin by the commandment might become exceeding sinful.
14 For we know that the law is spiritual: but I am carnal, sold under sin.
15 For that which I do I allow not: for what I would, that do I not; but what I hate, that do I.
16 If then I do that which I would not, I consent unto the law that it is good.
The law that is spiritual is about the "law of God after the inward man". But Paul is going to define another law here governing sin in our flesh.
17 Now then it is no more I that do it, but sin that dwelleth in me.
18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
He is talking about sin dwelling in his flesh, not in his 'inner man'. Later Bible versions really mess translation of this up with confusion of a 'sin nature', when the KJV doesn't. Paul points sin directly to the flesh. Later Bible translations that try to get away from pointing to the flesh being under sin do so to serve those who think Christ's Salvation is to a new flesh body, which certainly is not so per God's Word. That's one of the reasons they don't like this KJV translation.
19 For the good that I would I do not: but the evil which I would not, that I do.
20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.
21 I find then a law, that, when I would do good, evil is present with me.
Apostle Paul, a chosen vessel by our Lord Jesus Christ to take The Gospel especially to the Gentiles, admitted that oft when he tried not to sin, he found himself sinning. He admitted that he was also under a law that dwelt in his fleshy members.
22 For I delight in the law of God after the inward man:
There he recounts "the law of God after the inward man", as the spiritual side us.
23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.
There again Paul repeats that sin in his flesh wars against his inner man, showing how our spirit/soul inside our flesh wars with it causing us to sin.
24 O wretched man that I am! who shall deliver me from the body of this death?
25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
KJV
By that Paul is admitting that he, the real part, the inner man, will continue to serve the law of God, but his flesh will continue in the law of sin, for our flesh is sold under sin, and is destined to perish with this present world. It is NOT our flesh that is saved by Lord Jesus; it is our spirit with soul that is saved.
This is why the type body of the resurrection which Paul showed in 1 Corinthians 15 is to a "spiritual body", a body of incorruption, the body of that other dimension which is of the world to come.
However, if you are still in doubt, there are 8 reasons in Scripture that show us that Paul is indeed talking as a Pharisee (recounting his past experience) and he is not talking in the present tense as a Christian in Romans 7:14-24.
#1. In Romans 7:6, Paul says we should serve in newness of the spirit and not the oldness of the letter (Which is the Old Law and not the New Testament Scriptures that were still being formed). We are told to SERVE. How do we serve? Do we just do our own thing? No. We follow God's commands in the New Testament. This talk of the Old Law is the context of verses 14-24.
#2. We are dead to the Law by the body of Jesus Christ (Romans 7:4). Would this be the Old Law or ALL law? 1 John 3:23 is a commandment that says we are to believe on the Lord Jesus Christ. This is a New Covenant Law. So obviously we are not dead to this Law or Command. The Scriptures also say, "but now commandeth all men everywhere to repent." (Acts 17:30). Are we dead to this Law? Surely not. Jesus said "repent or perish." (Luke 13:3). Peter told Simon to repent (by way of prayer to God) of his wickedness of trying to pay for the gifts of the Holy Spirit so that he may be forgiven (Acts 8:22). Sin is merely transgression of the Law (1 John 3:4). All this lets us know that men of God can break God's laws and they can be separated from GOD because of it. So surely some kind of Law of God is still in effect and has dire consequences for any person's soul who commits them. For Jesus said that if we do not forgive, we will not be forgiven by the Father (Matthew 6:15). If Jesus was talking to unbelievers, this would not make any sense. They would first need to accept Christ. So the only logical conclusion is that Jesus is talking to believers in Matthew 6:15. You do not forgive (i.e. you sin or break this law of God) and you will not be forgiven or saved. 1 John 3:15 says if you hate your brother you are like a murderer and no murderer has eternal life abiding in them. Again, you hate your brother (which can be a one time act) and you do not have eternal life. It's that simple. Also, Paul condemns circumcision several times. Galatians 5:2 is the biggest verse that condemns circumcision salvationism. Circumcision is an Old Covenant Law and it is not a New Covenant Law. Paul uses the word "law" when he speaks against circumcision. So we have to conclude that Paul is saying we are dead to the Old Covenant Law and not all Law. So again, this talk of the Old Law plays into verses 14-24.
#3. Paul says, "For without the law sin was dead." (Romans 7:8). He also says, "I was alive without the law once: but when the commandment came, sin revived, and I died." (Romans 7:9). This type of saying is nonsensical from a present tense reading as an adult Christian. The only way it sort of works is if Paul is referring to himself as a baby who had no knowledge of God's laws yet. But there are two problem with even that interpretation. One, this view does not seem as consistent with the phrase, "For without the law sin was dead" because even though Paul as a baby did not have any knowledge of the Law yet, the rest of the adult world would have the Law and sin would still be alive to them. Second, Paul says, "And the commandment, which was ordained to life, I found to be unto death. For sin, taking occasion by the commandment, deceived me, and by it slew me." (Romans 7:10-11). Okay, so if Paul grew up and became aware of the Law one day, how could the commandment be ordained to life at this point in his life? The commandment was ordained for life back in the time of the Law of Moses. Also, Paul found that "the commandment" was death unto him and that it slew him. There are no death penalties attached to the commands given to us under the New Testament. Death penalties are only associated with the Laws given to us in the Old Covenant. This is how the Law slew him. For breaking the Old Law could be a loss of his own physical life. So this is talking about the Old Law (and not all Law). So again, this talk of the Old Law plays into verses 14-24.
#4. Paul says, "But sin, that it might appear sin, working death in me by that which is good; that sin by the commandment might become exceeding sinful." (Romans 7:13). Okay. Let's break this down. Paul says, "But sin, that it MIGHT APPEAR SIN, works death in me." (Romans 7:13). Now, how can sin make it appear like it may not be sin? Well, if Jesus was raised and Saul (Paul) was still a Pharisee striving to obey the Old Law when the New Covenant Law was still in effect, the sin that Saul (Paul) was struggling with as a pharisee during that time would not really technically be sin in every case. For if Paul disobeyed certain Old Covenant laws while the New Covenant and it's laws were in effect, then Saul (Paul) is not really breaking any real commandments from God in every case. Hence, why Paul said, "...sin, that it MIGHT APPEAR (as) SIN." (Romans 7:13). The beginning of verse 13 is a foreshadow of what is to come in verses 14-24. Paul is stepping out for a brief moment as speaking as an Israelite living throughout history to speak of his condition as a Pharisee when he says, "...sin, that it might appear sin." In the second half of verse 13, Paul says, that sin by the commandment might become exceeding sinful." (Romans 7:13). This is saying that when God provided the written Law of Moses to his people, there would be a double accountability to keeping God's laws because they are written for all to see now. So an Old Testament saint would feel exceedingly sinful or guilty for breaking God's law back in the Old Testament times because he had in his possession a written down visual law clearly telling him what is right and wrong. So again, Paul is referring to the Old Law here and not all law. This talk of the Old Law plays into verses 14-24.
#5. Paul says in Romans 7:14 that he is carnal and is sold under sin; And yet in Romans 8:2, Pauls says he is free from sin. So unless Paul is contradicting himself, he is talking from two different perspectives.
#6. In Romans 7:25, Paul asks the question: "O wretched man that I am! who shall deliver me from the body of this death?" Asking this kind of question as a Christian does not seem consistent with Paul's following statement if he is already delivered thru Jesus Christ as a Christian. If a believer is delivered by Jesus, and is thankful of that fact, there would be no cry to ask any question that says, "Who shall deliver me from this body of death?"
#7. Here is the final nail in the coffin for this argument. Romans 8:3-4 says,
3 "For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit." (Romans 8:3-4).
So which Law did God send His Son for so as to condemn sin in the flesh?
It was the Old Covenant Law.
For when Jesus died on the cross, the temple veil was ripped from top to bottom letting us know that the Old Testament laws were no longer valid because the Old Laws on the animal sacrifices and the priesthood were no longer acceptable.
Jesus Christ was now our Passover Lamb.
Jesus Christ was soon be our Heavenly High Priest (after He ascended to His father after His resurrection 3 days later) so He can be our mediator between God the Father and man.
Romans 8:4 says, "That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit."
This is saying that the righteous part or aspect of the Old Law can be fulfilled in us.
Paul says elsewhere,
8 "Owe no man any thing, but to love one another: for he that loveth another hath fulfilled the law.
9 For this, Thou shalt not commit adultery, Thou shalt not kill, Thou shalt not steal, Thou shalt not bear false witness, Thou shalt not covet; and if there be any other commandment, it is briefly comprehended in this saying, namely, Thou shalt love thy neighbour as thyself.
10 Love worketh no ill to his neighbour: therefore love is the fulfilling of the law."
(Romans 13:8-10).
So loving your neighbor is the righteousness of the Old Law!
We fulfill this law by walking after the Spirit and not after the flesh (i.e. sin).
So we see a consistent theme here. The word "law" used in general (with no actual description attached to it) is in reference to the Old Law in Romans 7 and Romans 8. This helps us to understand that Paul is telling us his past experience or life as a Pharisee in struggling to keep the Old Law unsuccessfully because he did not have Jesus Christ yet (in verses 14-24).
#8. In addition, in Romans 8:2, we see the mention of how there are TWO laws. We also learn from this verse that keeping one of these Laws helps us to be set FREE from the other one.
In Romans 8:2, we see:
Law #1. - Law of the Spirit of Life in Christ Jesus.
This is a New Covenant Law that we are still under. What is this Law?
It is fulfilling the righteousness of the Law (i.e. to love your neighbor - Romans 13:8-10) by walking after the Spirit (See Romans 8:3-4).
Law #2. Sin and Death.
This is in reference to the Old Covenant Law as a whole (i.e. the 613 Old Testament Commands within the Torah). It is called the Law of Sin and Death because you could physically be put to death by not obeying this Law.
What is the relationship of these two laws in Romans 8:2?
Keeping the New Law helps us to be free of the Old Law.
For there is no condemnation to those who are in Christ Jesus who WALK not after the flesh, but after the Spirit. (Romans 8:1).
Source used for a small paragraph within this write up:
http://www.thegoodbookblog.com/2012/apr/27/paul-is-not-talking-about-himself-why-i-take-the-p/
