Logical arguments. In all philosophies, theologies there is a basic assumption that structures all the following conclusions.
I think the fundamental point by the grace is enough camp has been revealed. We are doomed to be slaves to sin because sin is derived from impure thoughts and good deeds we wish we did but failed.
If you accept this premise, that however the grace of God works in your heart as a sinner you can never walk in righteousness, accept you are lost. Now the flip side of the argument is people who say at any point in their lives say they are walking in righteousness are hypocrites because it is impossible, whether you know the sin or not, so they must be pharisees.
But Paul though he admits we can walk in the flesh says in the Spirit we are slaves to righteousness. The image is of continual refreshing, cleansing, transformation, going from one state of glory to another.
Now the counter argument is if you say I am righteous, with past sin forgiven and you walking correctly, you are denying the need of Christ. But Jesus said something different. You will find you are a "good" person, but this is totally founded on the vine, the life of the Spirit within you. If you get tempted to believe it is you alone who now is righteous, you will slowly wither and die.
So fundamentally the standard for sin is crucial to your view. The strange thing is the law is actually less harsh than this idealism, so those who hold the standard this way are actually creating a new law of condemnation of their hearts.
Paul preached real grace, accepting the failures and seeing yourself in the light of Jesus's love. We sin because we do not see the sin, the hurt the damage and do not care. Listen to your heart when you hurt another and you will begin to understand.
Now I have a real understanding how love and forgiveness work, because I live it. Jesus commands us to live it as well. Whether this is perfection, we are called not to judge, but to repent when convicted of sin. If the law shows us failure, surely our hearts should listen, not the letter but to what the Spirit teaches us about the issue.
Why do you condemn yourselves over issues the Lord is sad about but does not call sin?