The willingness to think the unfamliar
We often think that someone who is blind, in the spiritual sense, is someone who is ignorant. We say things like, "He can’t see how much his wife loves him." But more often the difficulty is that the person will not see. It is a matter of the will.
Why would someone choose not to see? There is a glimmer of the answer here. The Pharisees have a sense that they alone, are the ones who truly understand the Law. Since they believe this to be so, anyone who contradicts this must be in error. A man or woman is a prisoner of whatever holds him or her back. The Pharisees were prisoners of their own darkness. That darkness was self-inflicted in the sense that they were unwilling to think the unfamiliar, unwilling to see something new.
Have you ever stumbled around in the dark and banged your knee on a table? There is no sense in saying, "I can't see the table, therefore it doesn't exist, therefore I can't have banged my knee against it, therefore my knee doesn't hurt." Reality has a way of banging us in the knee. This is because God created the universe so that sin would have consequences, and those consequences would convince us that we indeed are sinners. If you refuse to see the consequences—call them bad luck—then you are a prisoner of your own darkness. The only solution is to turn to the Light of the World—and never walk in darkness again.