Remain in sin?

What is important in the atonement is that a person is now in Christ, a member of the body of Christ. The lack of attention to this New Testament emphasis has at times led to the notion that the atonement is a legal fiction: God treats us as just, but we are still the same old sinners. On this, the New Testament is clear—we are not the same old sinners. If we remain in sin, then we are not in Christ, and if we are not in Christ, then Jesus died in vain.— Shalom, page 57

<idle musing>
Really, I didn't do this on purpose! The two books are just lining up that way. But I love it! Must mean it's important : )
</idle musing>