One of the most difficult concepts in Christianity is the concept of reprobation. While the Bible repeatedly tells us that God takes no pleasure in the death of the wicked (Ezekiel 18:32; 33:11), and that He doesn't want any to perish (2 Peter 3:9), but wants all to repent and be saved (1 Timothy 2:4), we are also faced with the harsh reality that He has also decided that this will not be the case. There are people whom God will not save. They will not repent, and in some cases, God will actually deliver them over to strong delusions (Romans 1:24-32; 2 Thessalonians 2:11). We are told that God even makes for Himself the wicked for the day of doom (Proverbs 16:4), and that He shows longsuffering to them so that He can show His wrath, and make His power known (Romans 9:22).
These are some very difficult things, both to understand and to accept. It is difficult to understand because it seems almost contradictory. It is difficult to accept because let's be honest, the "darker" half of the "contradiction" is not a nice thing to think about.
The first thing we need to understand about reprobation is that we don't really need to understand it. As Christians, by definition, we are not reprobate. God has clearly not chosen us for destruction, because, well, look at the lengths He went to in order to not destroy us. He left the glory of the Father, took on the flesh and blood of a man, submitted Himself to human powers, died a brutal death on the cross, and asked nothing in return for that but faith. If you believe in the name of the Son of God, you know you have eternal life (1 John 5:13). There are reasons God saw fit to tell us about reprobation, but they are not to cause us to worry. Perhaps they are a warning to would-be apostates and Liberals: "Apostatise, I might not let you back." Perhaps they are a warning to unbelievers: "This is what's coming if you don't repent." Personally, I think they are extra motivation to the faithful to be grateful. God could have abandoned me in spite of the cross, and yet here I am, my faith as strong as the day I was saved.
But of course, not everyone is given that. God deals differently with different people. To some, He appears visibly and demands repentance. Paul the Apostle, for example. Others, He leaves in the care of parents who will simply train their child in wisdom and truth, so they will never depart. Some He converts by evidence. Some people just hear and get this feeling that maybe it's true, and they never leave. However God converts us, He obviously doesn't convert everyone. Billions of people throughout history have died without knowing Jesus as their saviour, and now only know Him as their Lord. And we can be positive that many who are alive today will never repent. These, too, will go to Hell, and God will not intervene.
Or apparently, He will. As I pointed out, the Bible even shows that God will give people over to their own delusions. This is the harshest judgement of all, and arguably the hardest thing to accept in scripture. It's hard enough knowing God will send people to Hell for refusing to repent, but seeing that He will give them over to it even while they still breath is very difficult. How do we, as Christians, deal with this?
First, just accept that God knows better than you do. No matter how intelligent you are, you just aren't qualified to judge God. You do not need to know why God enforces a certain judgement. Just be grateful for how He judged you: Guilty, and yet in Christ, forgiven. You are the guilty gone astray, and yet you are the sheep the Shepherd left the flock for. The prodigal son granted a safe and welcome return back into the household, not as a slave, but still as a son.
But this question may still be in your mind, and so let us still ask it, and try to answer. For this, let us look to Pharaoh. This was a hard hearted man, determined to oppress the people of God. Note how both God and Pharaoh are given credit for the hardening of Pharaoh's heart. But Pharaoh's hard heart is seen before God does anything. In Exodus 3:19, before any plague, before any warning, before Pharaoh is even aware of God, God says "I know Pharaoh will not let them go unless he is forced by a heavy hand." Pharaoh didn't need God to harden his heart! He was already stubborn.
From this, we see how God's foreknowledge plays a heavy role. In fact, on the flip side, God even tells us outright that "whom He foreknew, He also predestined to be conformed to the image of His Son..." (Romans 8:29a, emphasis mine). Similarly, those whom He foreknows will serve a different purpose. This is something we see in Jeremiah 18. Here, God sends Jeremiah to a potter, who sets out to make a clay vessel. However, the clay messes up, so the potter instead makes a different vessel. God's message to the people of Israel: "O house of Israel, can I not do with you as this potter? Look, as the clay is in the potter’s hand, so are you in My hand, O house of Israel!"
And so are we. If we will not fulfil God's desires, He can still find a use for us. If we harden our hearts against Him, He will harden them further. One way or another, we will glorify God, be it through our salvation, or even our damnation. This, we again see through Pharaoh. "But indeed for this purpose I have raised you up, that I may show My power in you, and that My name may be declared in all the earth." (Exodus 9:16). In hardening Pharaoh's heart, God spread His name far and wide. God didn't harden Pharaoh's heart as some kind of joke, but to glorify Himself.
And did Pharaoh not deserve this? Is it not salvation that is, in a sense, unjust? As sinners, we do not deserve salvation. It is a gift bought for us at God's expense, not a wage owed to us. But hardening? We earned that. If God hardens our hearts, that is perfect justice. God simply locks you in to your choice.
But even then it's not necessarily permanent. After all, God is still glorified more by salvation than wrath. So perhaps, after one has served the purpose of the hardening, one may still come to faith. In fact, what if the purpose of the hardening is to come to faith? Hardening leads to a Hell that only God can save one from. And so in that hardening, perhaps salvation may come.
As you can see, this is a very difficult area of study. In fact, I strongly doubt I have done it any justice. As always, I would like to encourage prayerful and diligent study in this topic.