The Pharisees were blind.  They could not see spiritually (Matt. 23:16-28).  Nicodemas could not get his mind off of a physical birth (John 3:1-8). Some have sight but not others (Matt. 13:13-16).  God opens the eyes of the humble and shuts the eyes of the proud (Matt. 11:25,26). The blind can not see the entrance to the kingdom because it is a birth of the spirit, not of the flesh (John 3:6-8). “Except a man be born again, he cannot see the kingdom of God” (John 3:3).  Without being born of God the person remains a natural man and can not see spiritually (1 Cor. 2:14).  He describes the initial seeking after God as feeling after Him like blind men (Acts 17:26).  One reason that not everyone who seeks to enter will be able (Luke 13:24) is that they can not see it.  Jesus told them apostles “But blessed are your eyes, for they see: and your ears, for they hear” (Matt. 13:16).  God sends a strong delusion when a man does not love his truth (2 Thess. 2:10-12).  Thus not everyone can see it.  The kingdom is spiritually discerned (1 Cor. 2:14).  It is not possible to see a spiritual birth with physical eyes.  No one would be able to say Lo the kingdom is here! or, lo the kingdom is there!  Why?  Because Jesus said, “The kingdom of God is within you” (Luke 17:20, 21).  God’s kingdom is a spiritual kingdom, not a physical one.  And so today, as then, there are many who are not able to see the spiritual kingdom because they are spiritually blind.