Here is Romans 5.20 in the ESV: “Now the law came in to increase the trespass, but where sin increased, grace abounded all the more…”

Looks just fine, doesn’t it? English translations typically use a contrasting conjunction (“but”) when the Greek word could just as easily mean “and.”

But why did God send the law for the purpose of increasing the trespass? Might it not have been done to make grace abound? Didn’t Israel’s sin culminate in the crucifixion of Jesus? In which case, “their trespass means riches for the world, and … their failure means riches for the nations” (from Romans 11).

And if we look at how this passage leads into the question/accusation in 6.1, the contrast looks even shakier.

Now the law came in to increase the trespass, but where sin increased, grace abounded all the more, so that, as sin reigned in death, grace also might reign through righteousness leading to eternal life through Jesus Christ our Lord. What shall we say then? Are we to continue in sin that grace may abound?

Typically, people treat the question in Romans 6.1 as dealing with everything Paul has said in chapters 1-5. But wouldn’t it make more sense, since Paul brings up the question at this precise point in his letter, to consider that the question follows from the last thing Paul wrote before the question? In which case, I propose we eliminate the contrast and make it simplter:

Now the law came in to increase the trespass, and where sin increased, grace abounded all the more, so that, as sin reigned in death, grace also might reign through righteousness leading to eternal life through Jesus Christ our Lord. What shall we say then? Are we to continue in sin that grace may abound?

So God sent the law to increase the trespass so that Jesus would be presented as a propitiation through Israel’s culminating sin and the wrath that should have fallen on the planet is received by him instead. God “condemned sin in the flesh” (Romans 8.3) and thus made grace abound. So since God used sin to produce grace, Paul’s opponents mock him by asking “Are we to continue in sin that grace may abound?”