What does Romans 5:20 mean?

In describing the impact of Adam's disobedience in the previous verse, Paul wrote that "many were made sinners." By that, he means that all who were born after Adam were born into sin. By nature, they sinned. However, Paul has also revealed that those living between Adam and Moses were not under the law. In that way, their sin was not counted against them. They still sinned, and they still died as a result of sin, but their sin was, in a sense, not measured (Romans 5:13–14).

So what happened when God gave the law to Moses? How did that change this relationship between human sin and God? It made everything much, much worse, exactly as God intended. Once God gave actual commands about what to do and what not to do in this life, human beings moved from simply being sinners by nature to becoming actual lawbreakers. The existence of God's commands criminalized their sin—our sin—at a new level. Now we were all living in blatant, open rebellion.

In that sense, sin increased. It's not necessarily that people started sinning in greater volume, it's that our sin began to be counted against us as individual acts of rebellion against the will of God. It became an even more overt disobedience to Him. In fact, as Paul reveals in a startling statement, that's one reason God gave the law to the Israelites. He wanted to increase the trespass, the lawbreaking! He wanted it to be deadly clear just how sinful human beings were.

Paul follows that with another extraordinary statement, however. As human sin increased, grace "super-increased." God's grace abounded even more. This makes logical sense and yet it is still astounding to us. God's grace—giving good to us when we have earned bad—cannot be overwhelmed by our own sinfulness. The more we sin, the more grace God gives. In the following chapter, Paul will deal with a common abuse of that idea: the claim that sin is actually good, since it provides God more opportunity to show grace.