God exercises sovereignty over both physical sight and spiritual understanding, and at times He blinds as He works out His purpose. He struck the Sodomites with blindness, answered Elisha's and Paul's prayers to blind enemies temporarily, and struck Paul himself blind on the Damascus road. Exodus 4:11 declares that He makes the seeing and the blind. Blindness may result from sin, as in Deuteronomy 28:28-29, where He promises madness, blindness, and confusion of heart for disobedience. This mental blindness is the worst curse, because people cannot discern the cause of their troubles or turn to repentance, as the nations of Israel now show. At other times He blinds for another purpose He is working out. Jesus came so that those who see may be made blind (John 9:39), and John 12:37-40 and Romans 11:7-25 teach that God blinded Israel and hardened its heart. Healing without repentance would reward wickedness, and He is working with the elect first. He will restore Israel's understanding in the future, after the fullness of the Gentiles comes in. God's blinding is usually a temporary withholding of full understanding, or a judgment. Satan, by contrast, deceives and distorts truth, and Scripture never shows him opening or closing eyes. People also blind themselves by refusing truth they dislike, and God then gives them the delusion they prefer. Because Scripture calls only God the One who blinds, and never names Satan a god, "the god of this age" in II Corinthians 4:4 should be understood as God Himself.

God purposely blinds people who have been wicked and hardened in their rejection of Him. In Isaiah 6, after cleansing and sanctifying Isaiah and commissioning him, God tells him to go and tell the people, "Keep on hearing, but do not understand; keep on seeing but do not perceive," to make their hearts dull, their ears heavy, and their eyes shut, lest they see, hear, understand, return, and be healed. Because of their enmity toward God and their hard hearts, He blocked their ears and eyes so that they would have to go through exactly what Isaiah warned them of. Isaiah still gave them the warning of what was coming. Only after they suffered the consequences would they understand what he had said earlier. Their hard-heartedness meant that this was what it took to teach them. God always sets up His prophets directly, and the One who cleansed and sanctified Isaiah does the same with His people today.

God purposely blinds people who have been so wicked in rejecting Him and so hostile toward Him. After cleansing and sanctifying Isaiah before His throne, God commissioned him to tell the people, "Keep on hearing, but do not understand; keep on seeing but do not perceive," and to make their hearts dull, their ears heavy, and their eyes shut, lest they see, hear, understand, return, and be healed. God still told Isaiah to give them warning of what was coming, but He blocked their ears so that they would have to go through what He warned them of. Their hearts were so hard that only going through the consequences could teach them. Afterward they would understand what Isaiah had warned earlier. The blinding is therefore a purposeful act of God's judgment, intended to produce understanding through experience once warning alone had been rejected. It comes through a prophet whom God Himself directly sets up, as He did with Ezekiel and Jeremiah, and not one who sets himself up.