A man without the Holy Ghost is a blind man. He may not know it but that's what blindness is all about. A blind man is not just someone who cannot see, he can see alright, but all he sees is darkness. It's the same thing in the realm of the spirit. A blind man in the realm of the spirit is one who doesn't know the things of the spirit, he can't see the things of the Spirit of God. But when the Holy Spirit comes into your life, you will no longer be blind because He will cause you to see what others can't see.