Belinda wrote:The only thing I can say is that a philosophical zombie, such as Mary the Colour Scientist although a useful thought experiment, is impossible because there is no firm division between what an experience feels like and what it looks like from the outside as it were. I think that the two descriptions of the same event are true but use different sorts of language, one mentalistic and the other physicalistic.
I don't think Mary is a philosophical zombie. A P-zombie is indistinguishable from a normal human being except that it lacks conscious experience, aka qualia. Mary does have those things, when she is in the black and white room she has conscious experiences of black and white, and when she goes out of the room she has conscious experience of red.
This fascinating and extremely promising research: http://www.wired.com/wiredscience/2009/09/colortherapy/
demonstrates that the circumstances described in the Mary thought experiment are certainly possible.
All male squirrel monkeys lack the receptor chemical in the retina which allows perception of red and green. The same deficit is responsible for the most common form of colourblindness in (male) humans. Female monkeys see red and green (and yellow and blue). Monkeys were trained to touch a screen for a small reward (grape juice) when coloured patches appeared. Male monkeys ignored red and green patches, which were indistinguishable from grey for them, but responded to yellow and blue. Female monkeys responded to all four colours.
Gene therapy was used to introduce the missing receptor chemical (l-opsin) into the retinas of two male monkeys. After a delay of some weeks, they began to respond to red and green.
The same procedure could be used with humans, and almost certainly will be used, probably within the next decade. Similar therapy has already been used to allow previously totally blind humans to experience light.
Qualia is a way of talking about phenomenal consciousness, "what it is like" to experience things like light and colour. Before their treatment, the blind humans didn't know what it is like to see light, the colourblind monkeys didn't know what it is like to see red. Now they do. Qualia exist.