The first eleven chapters of Romans dealt with basic concepts, concepts that were strange to most converts. The foundation of righteousness is not correct acts that follow proper procedure. Righteousness results from trusting God. They found it extremely difficult to understand that a person could not make himself or herself righteous by performing the proper human acts. The Christian does not achieve personal righteousness through obedience, but the Christian responds to being made righteous by obediently serving God.
Every person needs a way to be saved that is based on trust rather than human achievement.
Human failure condemns every person including the godless and the expert. Everyone from the most ungodly person to the most knowledgeable expert of scripture needed forgiveness. Forgiveness could not be granted to anyone on the basis of human merit or human deservedness. Faith was the means for anyone to be righteous before God. Everyone from the ungodly to the moral judge could become a believer.