Do you know the idea of "Qualia"? Qualia is simply stated as a feeling, which is like a feeling that I feel the sky is blue, I feel excited while watching my favorite movie, or I feel tired of my leg. Have you ever heard of the story of Mary's Room? This is a thought experiment which was proposed by Frank Cameron Jackson, Australian philosopher. Mary is a great scientist and she knows everything about a color (optical characteristics, a structure of eyeball, a connection of optic nerve, and etc). But she has never seen actual colors. Then what will happen to her when she first see colors? It must be certain that she will get some strong feeling, and this is Qualia.