Romans 5:13
king james version(kjv)
13.)For until the law sin was in the world: but sin is not imputed when there is no law.
+++++++++++++++++++++++++++++++++++++++++++++++++++++
If people don't know that they are sinning then they can say they didn't know but if there is a law then they can't say they didn't know.
In this is the wisdom of God manifest.
Men had lost a understanding of what right and wrong were. not realizing the gravity of their sin. now that is a problem because Sin separates us from God:
Isa 59:1 Behold, the LORD'S hand is not shortened, that it cannot save; neither his ear heavy, that it cannot hear:
Isa 59:2 But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear.
So God in His wisdom gave the law so that all would see their need of saving/10 commandments and also the method of salvation/sacrificial system. Which would lead to the only solution, Faith in God for the forgiveness of sins and His imputed righteousness.
This is not a truth that only came after Jesus as it is written:
Gen 15:6 And he believed in the LORD; and he counted it to him for righteousness.
So we see that even before the law one could be counted righteous by faith.
For even Noah taught such as it is written:
2Pe_2:5 And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly;
and again:
Heb_11:7 By faith Noah, being warned of God of things not seen as yet, moved with fear, prepared an ark to the saving of his house; by the which he condemned the world, and became
heir of the righteousness which is by faith.