Verses 3 & 4 speak of the gospel being hid (assuming it is spoken plainly) to those who are lost. What hides their eyes from the truth about Jesus? Satan here is called the god of this world. In Ephesians 2:2 Satan is called “the prince of the power of the air, or atmosphere.” He is also known as the spirit who now works in the sons (and daughters) of disobedience. I want to reserve the rest of this passage to dwell on the light that has shined in our hearts. This is the light of the knowledge of the glory of God in the face of Jesus Christ. In the next verse Paul calls it a treasure. Is this precious to you as it is to me? However, we have this in a vessel of clay. This means we are but dirt. I don’t deserve this. It is mine by the grace of God.