The theme of Romans leading up to chapter 9 is that Paul had written a letter with the Jews in mind, evidenced by the many Jewish themes throughout, including pointed questions aimed directly at the Jew. From the start, Paul identifies with the Jew by pointing out the depraved state of the Gentiles, and their condemnation under the Law. But then Paul challenges the Jew with a charge of hypocrisy, when they do some of the very same things as the Gentiles. Paul then points out the hopelessness of achieving righteousness through the Law, while simultaneously pointing out that not all was lost, since there were well known historical Jews such as Abraham, Moses and David who did, in fact, achieve a state of righteousness with God, and this is where Paul points out that it was not through the Law at all, but by faith. This becomes the perfect segue into Christ being the ultimate end of faith. Paul extols the riches of Christ and all that God has eternally stored up for those who believe in Him. That’s when we reach Romans 9. The standing question is that if Christ is the Messiah of the Jews, then why don’t the Jews believe in Him? There’s actually a long history there. God reached out to the Jews with many offers of grace, until God finally had enough, which resulted in their hardening, as recorded at Isaiah 6:9-10, in which God states that He will harden Israel so that they could not receive His Son, or at least, they would not receive His Son without first reconciliation with God. God was not going to have people reject Him, while instead embracing a conquering Messiah to deliver Israel from the Romans. So God sent Christ in the same image of the prophets whom the Jews persecuted before Him. Now Paul’s objective at this stage of Romans 9 was to develop the backdrop for the illustration of the Olive Tree described at Romans 11, in terms of the natural and wild branches, in which the natural branches were being cut off, for a time, so that the wild branches could be grafted in. What Paul was doing in Romans 9 was expressing his sincere passion for the Jew, which was also God’s passion, while highlighting the fact that God was now, as a result of Jewish unbelief, turning to the Gentiles in order to graft them in. Jesus warned the Jews with illustrations that this was going to happen. So Paul sets up God’s sovereign right to first choose the Jewish nation (by using examples like with Isaac, the one chosen to receive the inheritance, including his son Jacob), as the basis to suggest that God also has the right to choose the Gentiles, which validates Paul’s ministry of the Gospel to the Gentiles. In other words, if God has the sovereign right to choose the Jews, then it stands to reason that He has the same right to graft in the Gentiles. Additionally, He has the same right to harden the Jews, which is what He warned at Jeremiah 18:1-13 and what He did at Isaiah 6:9-10, and ultimately quoted as its fulfillment at John 12:36-43. When Paul asks the question of what right does the pot have in responding back to the Potter, this is a question aimed at the unbelieving Jews (or at least, unbelieving in the Messiah, Christ), in anticipation of their protest against God's hardening, in terms of the Jews, the natural branches, having been removed from the Olive Tree. But even despite the hardening, Paul points out that it is a "partial hardening" until the times of the Gentiles are fulfilled. So this is what I see going on in the book of Romans, and it has nothing to do with either Calvinism or Arminianism.