What is truth?

As we were talking in class on Monday one thing that really caught my attention was that one of the critiques of the Narnia books was that they are just fantasy and therefore can't hold any real meaning for us as readers. I was intrigued by the question that was posed as to what it is that makes something true. Personally I believe that sometimes, as the storyteller, it is easier to go about telling the truth through different means than just outright saying it. You could tell the same story different ways but sometimes the truth is easier to accept when it is coming to you through a different world than when it comes from our own; that the confession of wrongdoing by a faun in Narnia is more widely accepted than that same confession would be if it had been given by a human in England. Lucy, and therefore the reader, can look at Tumnus and tell him that he isn't horrible because of the setting. If the same situation had happened on this side of the wardrobe he couldn't have just sent her home and walked away. I believe that you can't dismiss a story just because of the genre that it falls into. What is fantasy anyway? What is it that makes it so that fantasy isn't the truth? What makes any story true or not? Is it necessary for a story to be believable for it to tell the truth? Sometimes the best way to tell the truth is to go outside of the world we live in and let someone else tell it for you.