If in Romans 1-5 Paul expounds the meaning of the gospel, then in chapters 6-8 he turns to a very important topic of how the gospel can change our life, especially our struggle with sin. The main question that Paul addressed in Romans 6 is found in v.15: “What then? Shall we sin because we are not under law but under grace?”
Indeed, if we are justified by faith alone (as Reformers have re-discovered), what incentive do we have to live a holy life? Why can’t we enjoy the best of two worlds – the sweetness of sin and the benefits of salvation?
To answer the question, Paul develops a metaphor where sin is personified as a slave master and we as his slaves, obeying all his desires. Righteousness is also personified as a slave master. What happens to us at the point of conversion is that we change slave masters and start serving righteousness instead of sin.
So Paul’s answer can be summarized as follows. You used to be a slave to a bad master, which would eventually lead to your death. Now you have become a slave to a good master, outcome of which is eternal life. Why would you ever want to come back to your former master and continue working for him (to sin)?
Many of us would find this answer unconvincing. So what if I occasionally serve the old master; after all it gives me a lot of pleasure? The new master’s job may lead to eternal life, but is boring and too restrictive!
The reason Christians can think like this is because
a) they don’t see slavery in their former lives
b) they don’t see freedom in their new lives
I think the best person to go if you need help understanding these concepts in the modern context is Tim Keller. He keeps referring to them again and again, in almost all his sermons. I have explained some of his ideas in my earlier post “Gotta serve somebody“. Go and read it. Listen to Tim Keller’s sermons. Think. But until you start seeing slavery in your old life and freedom in the new, you will never be able to completely understand why you should strive to be a good person if you have already been made right with God.