Are you blind?  That is one of those humiliating questions your wife asks you when the purse she asked you to retrieve for her is right in front of you, but you can't see it.  The immediate response is "Are you crazy?  No, I'm not blind." .... just to find out as she walks over and picks up her purse, that  for you, was obviously hidden under Harry Potter's 'invisibility cloak' a second ago.  It's a shameful feeling when that happens ... you just chuckle and sheepishlly move on.  However, when "Are you blind?" is asked regarding spiritual blindness, the matter is much more serious.  The Bible has a lot to say about spiritual and physical blindness ... and in the end, all the blindness spoken about in scripture is spiritual in nanture, and we never want to be spiritually blind.