Mary's Room
Mary is a scientist who knows everything there is to know about the physics of color, but has only ever seen black and white. When she finally sees red for the first time, does she learn something new?
Philosopher Frank Jackson introduced this thought experiment in 1982 to argue that there are facts about consciousness that physical science cannot capture. If Mary already knew all the physical facts, but still learns something new when she sees red, then not all facts are physical facts.
Jackson, F. (1982). Epiphenomenal Qualia. The Philosophical Quarterly, 32(127), 127–136.
The setup
Mary is the world's greatest color scientist. She knows the wavelengths, the neural pathways, the way photons interact with cone cells, the precise brain states that correspond to seeing red. She can explain everything physical about color vision in complete detail.
She has lived her entire life in a black-and-white room. She's never seen color.
One day she walks outside. She sees a red rose.
Does she learn something new?
The knowledge argument
Jackson's claim: yes, she does. She now knows what it is like to see red, and that's something her physical knowledge didn't give her.
If this is right, it's a significant conclusion. It means phenomenal experience, the felt quality of sensation that philosophers call qualia, is something over and above the physical. Complete physical knowledge leaves something out.
The physicalist replies
Not everyone agrees that Mary learns a new fact:
- The ability hypothesis: Mary doesn't learn a new fact. She gains a new ability: to recognize, remember, and imagine red. No new propositional knowledge, just new skill.
- The phenomenal concept strategy: Mary learns a new way of representing an old fact. The fact is physical; the mode of access is new.
- Denial: Mary doesn't actually learn anything. She's merely gaining the experience she already fully understood. The surprise is psychological, not epistemic.