Spiritual blindness

“Jesus said, “For judgment I came into this world, that those who do not see may see, and those who see may become blind.” Some of the Pharisees near him heard these things, and said to him, “Are we also blind?” Jesus said to them, “If you were blind, you would have no guilt; but now that you say, ‘We see,’ your guilt remains.” (John 9:39-41 ESV)

The devil has blinded the minds of unbelievers to keep them in the dark

“In their case the god of this world has blinded the minds of the unbelievers, to keep them from seeing the light of the gospel of the glory of Christ, who is the image of God.” (2 Cor. 4:4 ESV)

God gives light to shine in our hearts

“For God, who said, “Let light shine out of darkness,” has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ.” (2 Cor. 4:6 ESV)

Jesus is the light of the world

“Again Jesus spoke to them, saying, “I am the light of the world. Whoever follows me will not walk in darkness, but will have the light of life.” (John 8:12 ESV)

Therefore…

“For at one time you were darkness, but now you are light in the Lord. Walk as children of light.” (Eph. 5:8 ESV)