OK, maybe it was too difficult. Here's another approach: A man can appear to be blind because he does not have visual experience. He appears to be blind because he is really blind. A man can appear to be blind because he is lying about the fact that he is not blind. He is not really blind. A man can appear to be blind because he is not capable of understanding his visual experiences. He is not really blind but doesn't know it. Given the above, we have tautologically defined "real blindness" as "lack of visual experience". This is not just a semantic game. Because our definition is tautological, everything that is true about "real blindness" is also true about "lack of visual experience". It is true that really blind people cannot lie about the fact that they are really blind. It is not true that people who are not really blind can lie about the fact that they are not really blind. Therefore: The belief that someone can be really blind and lie about that fact is based on a false notion A corollary: If a man behaves as if he's not blind, then we have no basis to believe in the possibility that he doesn't have visual experience Come on, where is the "we have no way to know if other people have experiences" crowd?