The following is an excerpt from The MacArthur New Testament Commentary on Romans 9:18-20.

So then He has mercy on whom He desires, and He hardens whom He desires. You will say to me then, “Why does He still find fault? For who resists His will?” On the contrary, who are you, O man, who answers back to God? The thing molded will not say to the molder, “Why did you make me like this,” will it? (Romans 9:18–20)

A question, or objection, that Paul anticipates and responds to is: Why does God then still find fault? For who resists His will? In other words, if God sovereignly has mercy on whom He desires and hardens whom He desires, how can human beings be held responsible? How can they be blamed for their unbelief and sin, when their destiny has already been divinely determined? Again, such reasoning challenges God’s justice and righteousness.

As Israel was conquering Canaan, “Joshua waged war a long time with all these [Canaanite] kings. There was not a city which made peace with the sons of Israel except the Hivites living in Gibeon; they took them all in battle. For it was of the Lord to harden their hearts, to meet Israel in battle in order that he might utterly destroy them, that they might receive no mercy, but that he might destroy them, just as the Lord had commanded Moses” (Josh. 11:18–20).

Such commands of God, with which the Old Testament abounds, seem totally capricious and cruel to worldly, carnal minds,  which accept only what fits their preconceived ideas of right and wrong, justice and injustice. Consequently, they judge even God by their own finite, biased, and sin-tainted standards.

God’s utterly sovereign will is just as clearly taught in the New Testament. Later in this letter to Rome, Paul tells his readers: “That which Israel is seeking for, it has not obtained, but those who were chosen obtained it, and the rest were hardened” (Rom. 11:7). In his first letter to Thessalonica, he declares that “God has not destined us [believers] for wrath, but for obtaining salvation through our Lord Jesus Christ” (1 Thess. 5:9).

In His perfect wisdom, and in perfect righteousness and justice, God has destined some people for salvation by His grace and, because of their sin and unbelief, has left others to damnation by His wrath. Speaking of unrepentant unbelievers, Peter writes, “These, like unreasoning animals, born as creatures of instinct to be captured and killed, reviling where they have no knowledge, will in the destruction of those creatures also be destroyed” (2 Pet. 2:12).

Many critics of such doctrine, supposedly coming to the defense of God’s justice, fail to acknowledge that every human being since the Fall has deserved nothing but God’s just condemnation to an eternity in hell. If God were to exercise only His justice, no person would ever be saved. It is therefore hardly unjust if, according to His sovereign grace, He chooses to elect some sinners for salvation.

It is not, of course, that we can fully understand what God reveals about His sovereign election and predestination. It can only be accepted by faith, acknowledging its truth simply because God has revealed it to be true. As believers, we know that, in ourselves, we deserve only God’s rejection and condemnation. But we also know that, for His own sovereign reasons, God has elected us to be His children and, in His own time and way, brought us to saving faith in Jesus Christ. On the other hand, we also know that our human will had a part in our salvation. Jesus said, “All that the Father gives Me shall come to Me.” That is the choice of God’s will. But Jesus immediately went on to say that “the one who comes to Me I will certainly not cast out” (John 6:37). That is the choice of man’s will, which God graciously accedes to for all who believe in His Son.

Continuing simply to proclaim God’s sovereign righteousness and justice rather than trying to explain it, Paul turns a question back on those who would question the Lord. On the contrary, he says, who are you, O man, who answers back to God? In other words, it is blasphemous even to question, not to mention deny, God’s right to hold men accountable when they are captives of His sovereign will.

It is obvious from Paul’s wording that the ones who might be asking such questions would not be seeking God’s truth but rather self- justification. Attempting to excuse their own unbelief, sinfulness, ignorance, and spiritual rebellion, they would be apt to accuse God of injustice.

But because human understanding is so limited, even sincere questions about God’s sovereign election and predestination ultimately must go unanswered. As already noted, it is one of the many truths about God that we must accept by faith, simply because He has revealed it in His Word.