Mary's room

From Pin Eight
Jump to: navigation, search

In philosophy, Mary's room is a thought experiment intended to prove the existence of knowledge of non-physical facts or qualia.

Mary[1] lives in a research facility. The only light that reaches the area where she is kept is the monochromatic light of green LEDs, including the backlight of her LCD computer monitor. Mary has never left the facility since birth, yet she has a degree in neurophysiology from an online university. She knows consciously about what goes on in the process of color vision, yet she has never seen color with her own eyes. Will she learn anything from exposure to red and blue light?

In the traditional exposition of Mary's room, nothing in Mary's room is colored, and her only source of information is a television. Because the color inherent in hair, eyes, skin, lips, food, and the like complicate the practicality of performing such an experiment, I replaced this with only monochromatic light sources. Nor is it specified how Mary can change what is shown on the television, making such a distance degree impractical; I clarified this with modern technology.

With access to public web sites, to scholarly journals, and to everything Amazon and Barnes & Noble have to offer on their respective e-book services, Mary has a lot she can read. We can assume that she has read an article on MIT about people blinded by cataracts from birth learning to see after corrective surgery[2] and people learning to see with tongue stimulation.[3] We can also assume that she has read the novel The Giver by Lois Lowry, which describes a fictional society dependent on strong antidepressants to suppress "stirrings", whose side effects include color blindness and tone deafness. The novel's protagonist appears immune to some of these effects, and he notices a strange "differentness" about an apple and another character's hair. And perhaps, to continue the "green" theme, she rented The Matrix on Netflix and heard the character Cypher mention seeing "blonde, brunette, redhead" after having read Matrix code for so long.

If anything, Mary will not be very surprised. If she is aware of the scientific literature about the brain's adaptation to novel sensations, she should be able to imagine what will happen next: things will look "different" as the red-green and blue-yellow parts of the optic nerve start to return structured signals for the first time, and then her brain will reorganize itself to sort out this "different" sensation. In fact, she might have previously rigged her computer to display red and green fields in alternation using green light, as if it were displaying an undecoded field-sequential signal, and learned to process various flicker depths or dot patterns as saturation. The remaining debate among philosophers is about how to classify knowledge of how to process sensory input.


  1. Mary is an incredibly common name throughout the Abrahamic world. I personally would have chosen a slightly less Bob name to make the name of the thought experiment more distinct, or at least given her a surname, but the existing philosophical literature uses "Mary's room".
  2. Anne Trafton. "MIT study shows those who once were blind can learn to see". MIT News. 2007-12-14. Accessed 2011-10-06.
  3. Michael Abrams. "Can You See With Your Tongue??" Discover. 2003-06-01. Accessed 2011-10-06.