What does Romans 7:8 mean?

Paul has rejected the claims of his critics that he believes the law itself to be sinful. Instead, he wrote in the previous verse that the law introduced him to sin. He learned, in a formal sense, what it means to covet another person's possessions from the law of Moses (Exodus 20:17; Deuteronomy 5:21). Now he describes how sin took advantage of that command to cause him to become covetous.

Two ideas are at work here. One is that human beings are naturally rebellious in our sinfulness. As soon as we hear about a legal restriction, we want to break it. The very existence of a law provokes us to want to sinfully cross that line. In that sense, the mere existence of the law is something our sin nature will use to encourage us to sin.

The other idea is this: God's law shines a spotlight into our hearts that allows us to discover the existence of sins we didn't even know about before. They were still sins, and they were still in our hearts, but the law reveals them to us. This relates to Paul's earlier comments about how without a law there is no "trespass," though there is still sin. With this in mind, Paul concludes the verse with a simple, profound statement: Apart from the law, sin lies dead. As Paul wrote in chapter 5, "sin is not counted [recognized] when there is no law" (Romans 5:13). Sin exists whether the law is known, or not, but knowing the law both highlights and, in some ways, tempts us with respect to sin.