Satan, who is the god of this world, has blinded the minds of those who don’t believe. They are unable to see the glorious light of the Good News. They don’t understand this message about the glory of Christ, who is the exact likeness of God. (2 Corinthians 4:4 NLT)
It's discouraging to share the Gospel with people and see that blank stare on their faces when you've finished. It makes you wonder where you failed in the presentation or if you should have used a different approach. The fact is, though, that the likely cause is Satan who "blind[s] the minds of those who don't believe." When you find yourself in that situation don't give up on that person. Pray, love, and share the "Good News" of Jesus Christ again (at a later time) until the light breaks through into their darkness.
