What does Romans 2:20 mean?

Paul is building a powerful "if-then" statement. The "if" aspect of this passage is about all of the benefits that come with being an Israelite. Those who are part of God's chosen people also have knowledge of the law of Moses. In the Jewish mindset, this made Israel the recipient of God's ultimate truths. This sets a high standard. Paul is setting his Jewish readers up for some hard questions in the following verses.

He has asked "if" such a person relies on the law, and boasts in God, and is sure he is a guide to the blind (Romans 2:17–19). Now, he includes the idea of such a person seeing himself as an instructor of the foolish people who do not have God's law. Does he see himself as a teacher about the law, as an adult to children? And if this Jewish person really has the law, God's law, which is the embodiment of knowledge and truth, then, Paul will ask in the following verses, why doesn't he perfectly follow the law?