What does Romans 5:13 mean?

In this section, Paul compares the effects of sin, from Adam, as compared to the effects of grace, from Christ. In the prior verse, he noted that it was the actions of one man which brought death and sin into the lives of all humanity.

Now, Paul seems to immediately take an aside from the main point of this section. He will pick that up again in verse 15. Here, though, he answers a question that may have popped up for some of his readers. How could there be sin before the law of Moses existed?

Paul seemed to suggest in Romans 4:15 that without the law, there is no sin, no "transgression." In context, Paul did not indicate the there was no actual sin, but only that one cannot literally "break" a law unless they are rightly subject to it. Here, Paul again clarifies that point: It's not that sin did not exist before the law of Moses. Of course, human beings have always sinned since the garden. Instead, Paul says that specific sin was not counted against specific people before the law. It was not a transgression in the sense of breaking the written words of the law; it was simply sinful humanity expressing its sinful nature: self-serving, hurtful, deceptive, and immoral.

The argument here, as in Romans 4:15, is entirely one of perspective. Humanity does not recognize sin when God does not give us something like the law: in our minds, those sins are not "counted." They are still sins, since we still ought to know better (Romans 1:18–20). The presence of the law does not turn righteousness into sin—it turns supposed ignorance into certain knowledge of our own wrongdoing.

Paul has shown that sinful nature every human being was born into resulted in separation from God and in inevitable death.