The Bible says that people will only believe the Gospel if God opens up their heart to it. If God has not opened up their heart to the Gospel, how can they be punished for unbelief? It's not a choice. Someone told me that God has opened up everyone's heart, but if that were the case, then more than half of the world, in fact, almost the entire world, would be Christians, because almost the entire world has heard the Gospel. If unbelievers don't believe because their heart is hardened, and their heart is hardened because God didn't open up their heart, how can they be blamed for unbelief? Something doesn't add up.