A believer in Christ might assume that anyone who truly understands the nature of the gospel would want the gospel. “Why wouldn’t they believe?” we might wonder.
Yet they don’t all believe. Even when we assume that they will and should, they do not believe.
A clear, but often overlooked illustration of this is in Isaiah 6. In that chapter the prophet sees an overwhelming vision of God’s glory and believes that he will be struck dead because of his sinfulness (v. 5). Yet God is gracious and grants and demonstrates redemptive forgiveness (v. 6) and then even asks and calls Isaiah to serve Him — and Isaiah is willing (v. 8).
And that’s where most sermons on Isaiah 6 end. The assumption is that Isaiah is redeemed and equipped and ready to serve God and all who hear his message will repent. Yet Isaiah is told by God that he would go as God’s emissary, but that he would be unfruitful. They would not believe:
“He said, “Go, and tell this people:
‘Keep on listening, but do not perceive;
Keep on looking, but do not understand.’ “Render the hearts of this people insensitive,
Their ears dull,
And their eyes dim,
Otherwise they might see with their eyes,
Hear with their ears,
Understand with their hearts,
And return and be healed.” Then I said, “Lord, how long?” And He answered,
“Until cities are devastated and without inhabitant,
Houses are without people
And the land is utterly desolate, “The LORD has removed men far away,
And the forsaken places are many in the midst of the land.” (Is 6:9–12)
It’s quite an astounding and sobering conclusion to a dramatic vision of God. Not everyone who hears the message of God will respond to that message.
Paul quotes this very same passage as he considers his ministry to the Jews in Rome (Acts 28:26-27). And in so doing, he reveals at least three things about the nature of unbelief.
Those who reject Christ reject Him until their hearts are hardened. If one persists in refusing the truth, He will eventually lose his ability to recognize the truth and respond to it (Ex. 7:13; 1 Sam. 6:6; 1 Tim. 4:2). There is a sense in which the hardening is self-hardening.
Those with hard hearts are intentionally hardened by God to accomplish His purposes. This is common in the economy of God. He did it with Pharaoh in the Old Testament (Ex. 7:13), and He will do it at the end of the age (2 Thess. 2:11-12). Why does the Lord do this? In part, so others will believe believe. So in Acts 28:28, Paul says that God chose to harden the Jews so they would reject Jesus as their Messiah so that the Gentiles (you and I) might be grafted into their national blessings.
Those who are hardened are not hardened against their will. It is what they want. Just as those who are drawn (Jn. 6:37, 44) are likewise not drawn against their will, those who reject Christ do not reject Him against their will. It is what they want. Those who reject Christ are not absolved of responsibility.
So, while we think that all men should believe, we must also rest in the truth that God is sovereign also over their unbelief and that He is working their unbelief to accomplish other purposes of His. (And when confronted with those who do not believe, we should like Paul be on the lookout for those who do want to believe.)