Paul's method was to provide evidence from Scripture. This is an effective strategy.
It had been a long day for the assistant at the cosmetic counter. Having been on her feet all day, she was looking forward to going home. Just before the doors closed, a man came running up to her frantically and said, “Tomorrow’s my wife’s birthday and I don’t have anything for her. What do you recommend?” The shop assistant brought out a nice bottle of perfume worth about £100. He gasped and said, “That’s way too expensive!” So she held up a bottle that cost £50. He said, “That’s still too expensive. What do you have that’s less expensive?” She searched some more and found something for £25. The husband replied, “That’s still too expensive! What else do you have?” She then brought out the cheapest thing she had at the counter, a tiny £10 bottle of perfume. He was now exasperated and said, “You don’t understand. I want you to show me something really, really, cheap!” She quickly reached under the counter, pulled out a mirror, told him to look into it and said, “Try this!”
The Word of God is like a mirror - we can see ourselves in it. James wrote: Anyone who listens to the word but does not do what it says is like a man who looks at his face in a mirror and after looking at himself, goes away and immediately forgets what he looks like. James1v23to24.
When it comes to paying attention to the Bible we can be like the man who took his portrait photos back to the photographer and said, "I want my money back, these pictures don't do me justice." The photographer looked at the pictures and said, "You don't need justice, you need mercy."
From John Reed's commentary on Romans 3:9-20