Mary is a color scientist who knows every physical fact one could possibly know about color experience, but she has lived her entire life in a black and white room where she never actually experiences colors for herself. Upon leaving her room and directing her gaze towards a bright red tomato for the very first time, she makes a discovery. She now knows what it is like to see something red. But if Mary already knew every physical fact one could possibly know about color experience, what sort of fact has she discovered? According to many anti-physicalists, Mary must have discovered a new non-physical fact. Furthermore, what Mary learned is something that virtually everyone already knows from their own experiences of color. Therefore, we must know non-physical facts about color experience as well and physicalism is false.
This thought experiment, developed by Frank Jackson, is one of the most famous arguments against physicalism in the history of analytic philosophy. Lots of ink has been spilled over it. However, I think it is one of those rare cases where we can be fairly certain that it fails for reasons that are basically uncontroversial.
In order for the argument to succeed, there must be some knowledge that Mary can only gain by having an appropriate experience. This could not be the case if Mary’s new knowledge involved ordinary concepts that could be shared through written or spoken language. If Mary’s new knowledge involved concepts that could be shared with her inside of her room, then she could learn what it is like to see something red from inside of her room just by hearing about it from a reliable informant. Consequently, if Mary’s experience provides her with special knowledge about color experiences, that knowledge must involve extraordinary concepts that cannot be shared in the usual ways.
This presents a fatal problem for Jackson’s argument: If anti-physicalists can appeal to extraordinary concepts that cannot be publicly shared (philosophers call these “phenomenal concepts”) in order to explain Mary’s discovery, then so can physicalists. In both cases, Mary’s discovery will be explained by her acquisition of new concepts that were not accessible from inside of her black and white room. Gaining new knowledge by using new concepts does not require one to learn about any new facts. One can acquire new knowledge of an old fact by thinking about it with the new concepts that one has acquired (For instance, even though I already knew that Clark Kent is Clark Kent, I make a discovery when I learn that Clark Kent is Superman). Consequently, Mary’s discovery does not require her to learn about any non-physical facts.
