When we first read Romans 3, we felt that there was some confusion in the logic.  For example, Paul   asked a question in the first verse: "What advantage, then, is there in being a Jew, or what value is there in circumcision?" (Romans 3:1, NIV).  Then he answered this question in the second verse.  He said: "Much in every way!  First of all, they have been entrusted with the very words of God."  Logically speaking, we would then expect Paul to say: "second or third" later, but we couldn’t find the second or third in chapter 3, nor in chapters 4 or 5.  When I searched online, I saw that it's not until Romans 9:4-5 before Paul talked about other advantages of the Jews.  So it's not that Paul's logic is unclear.  It's just that we don't understand his reasoning, making it difficult to properly interpret this chapter.