on qualia

Imagine a very young scientist, named Mary, who has lived her whole life in a black and white room. Mary is brought up by extremely smart experimenters who teach her almost everything there is to know about things, especially color. Whatever the experimenters haven't taught Mary about color, she learns herself through scientific observation. When I say Mary knows everything there is to know about color, I mean exactly that. She knows all the wavelengths, she knows exactly what goes on in the human eyes and brain when one experiences color, etc. One day, as an experiment, one of the observers throws a red tomato into the room. Does Mary learn something new? The answer is obviously yes. But what are the implications of this?

If we suppose that Mary knows all the physical facts about color, and yet she learns something new, by simply experiencing color, that must mean there are more than just physical facts to learn. It also means that there are some things we simply can never learn. For example, we can never know what it is like to be able to find our way through the house when the power goes out by using echo location. More specifically, we can never know what it is like to experience this in the same way that say, a bat would. We can learn all we need to know about echo location and sonar, and we can build machines, but we can never experience it as a bat would without being the bat. And its impossible for you or for me to be a bat. Because once I'm a bat, then I'm not me. So I'm not a bat.