In James Arminius’ commentary on the 9th Chapter of Romans, he argues that the topic at hand is justification by faith. He humbly admits that for some time the chapter was of the “greatest obscurity”, but he now sees it clearly. I can relate. Arminius finds Paul answering an implicit question by saying: though most of the Jews are rejected, yet the word of God does not therefore fail. Arminius spends some time grappling with the exact nature of the implicit question and concludes it was: “Does not the word God become of none effect, if those of the Jews, who seek righteousness, not of faith, but of the law, are rejected by God?" He basis this conclusion on Paul’s use of the “children of the promise” and “the children of the flesh”, which represent believers and those who attempt to attain righteousness through the law. He finds further support in the examples of Ishmael and Isaac, who represent the Law and the Gospel in Galatians 4. Similarly, with Esau and Jacob, we find God teaching that He hates those who seek righteousness through the works of the law, but loves those have faith in God’s call. So God’s plan all along was to justify through faith and His word isn’t overturned by the Jew’s rejection; it’s established by it.
Paul deals with the charge of injustice by pointing out that God’s choice was merciful (which presupposes sin), so it’s not a question of justice. When men will and run to obtain justification through the law, they are rejected, and do not obtain mercy through the Gospel. If God is free to declare His glory by punishing and hardening Pharaoh, He is free to punish those who seek salvation through the law. The hardening of Pharaoh (and the implication that the Jews were being hardened) gives rise to the object “why does He yet find fault, for who has resisted His will?” Arminius explains that hardening is a punishment for prior sins, and even though the person at that moment cannot avoid sinning, they are still responsible, because they deserved the hardening of freewill. Paul first reproves the objector for insolence and then explains that God forms sinners who reject His grace into vessels of wrath, and through grace forms people into believers and vessels of honor.