This chapter shifts its audience from Roman Christians to those who "judge" other people and do not believe in Jesus. (See: [[rc://en/tw/dict/bible/kt/judge]] and [[rc://en/tw/dict/bible/kt/believe]])
This phrase looks back at Chapter 1. In some ways, it actually concludes what Chapter 1 teaches. This phrase explains why everyone in the world must worship the true God.
Those who try to obey the law will not be justified by trying to obey it. Those who are justified by believing in Jesus show that their faith is real by obeying God's commands. (See: [[rc://en/tw/dict/bible/kt/justify]] and [[rc://en/tw/dict/bible/kt/lawofmoses]])
Paul uses several rhetorical questions in this chapter. It appears the intent of these rhetorical questions is to make the reader see their sin so they will trust in Jesus. (See: [[rc://en/ta/man/translate/figs-rquestion]], [[rc://en/tw/dict/bible/kt/guilt]], [[rc://en/tw/dict/bible/kt/sin]] and [[rc://en/tw/dict/bible/kt/faith]])
In context, "he will give eternal life" in verse 7 is a hypothetical statement. If a person could live a perfect life, they would earn eternal life as a reward. But only Jesus was able to live a perfect life.
Paul gives another hypothetical situation in verses 17-29. Here he explains that even those who earnestly try to obey the law of Moses are guilty of violating the law. In English, this is about those who follow the "letter" of the law but cannot follow the "spirit" or general principles of the law. (See: [[rc://en/ta/man/translate/figs-hypo]])
At times, this could be translated in a simpler way. But it is translated in this relatively awkward way because when Paul refers to "people who judge" he is also saying that everyone judges. It is possible to translate this as "those who judge (and everyone judges)."