Why are the eyes of unbelievers blinded from the truth of God's word?

Answer 1

This ,no doubt is a reference to (2 Corinthians 4:4) which states that the "God of this system of things has blinded the minds of the unbelievers, so that the illumination of the glorious good news about the Christ,who is the image of God, might not shine through." To Identify who the God of this system is read (Matthew 4:8,9) where Satan while trying to tempt Jesus offered him "All the kingdoms of the world, and said "All these things I will give you if you fall down and do an act of worship to me". This offer would have not been a temptation at all if Satan did not possess it. The Apostle John later declared 'The whole world is lying in the power of the wicked one'.At (Revelation 12:9) he is said to be misleading the entire inhabited earth.The only way one can protect themselves from Satan's influence is to come to know God (Jehovah), and his son, (Jesus Christ). This can be done with a personal study of The Bible, which Jehovahs Witnesses offer free of charge.

Answer 2

They are deceived by the great deceiver (Satan). Just as he deceived the first humans. "He said to the woman, "Did God really say, 'You must not eat from any tree in the garden'?" The woman said to the serpent, "We may eat fruit from the trees in the garden, but God did say, 'You must not eat fruit from the tree that is in the middle of the garden, and you must not touch it, or you will die.' " "You will not surely die," the serpent said to the woman. "For God knows that when you eat of it your eyes will be opened, and you will be like God, knowing good and evil." When the woman saw that the fruit of the tree was good for food and pleasing to the eye, and also desirable for gaining wisdom, she took some and ate it. She also gave some to her husband, who was with her, and he ate it." (Genesis 3)

Adam and Eve talked with God directly, and they were still tricked into thinking that what he said was not true.

"This is the judgment, that the Light has come into the world, and men loved the darkness rather than the Light, for their deeds were evil. For everyone who does evil hates the Light, and does not come to the Light for fear that his deeds will be exposed." (John 3:19-20)