What does Mary learn?
When she sees red for the first time, does physicalism fall?
I
Mary learns a new fact
Mary learns a fact about experience that was not among the physical facts. So physicalism is false.
- Best argument
- Before her release, Mary knew everything physical. After, she knows something she did not know: what seeing red is like. If she gained knowledge, there was something to know that physical knowledge did not include. The most natural explanation is that experiences have qualia, non-physical qualities.
- Strongest objection
- Learning something new does not show there is a new fact. You can learn a new way of thinking about an old fact: someone who knows that Hesperus is bright can learn that Phosphorus is bright, without learning a new fact about the world, since both are the planet Venus.
- Defended by
- Frank Jackson (1982), David Chalmers
II
Mary gains an ability
Mary does not learn a new fact. She gains new abilities: to imagine, recognise and remember red.
- Best argument
- David Lewis and Laurence Nemirow proposed the ability hypothesis. Knowing what an experience is like is know-how, not know-that. Mary already knew all the facts; what she lacked was the capacity that comes from having the experience. This is no more a refutation of physicalism than the fact that reading about swimming does not teach you to swim.
- Strongest objection
- Mary seems to gain propositional knowledge too. She can now think 'so this is what my research subjects were seeing', which seems to be a thought with true-or-false content she could not entertain before.
- Defended by
- David Lewis, Laurence Nemirow
III
Old fact, new concept
Mary learns an old fact in a new way. She acquires a new 'phenomenal concept' of something she already knew under physical concepts.
- Best argument
- On this widely held view, phenomenal concepts are special first-person ways of thinking about brain states, which can only be acquired by having the experience. Mary knew the physical fact about red-experiences under physical concepts; now she grasps the same fact under a phenomenal concept. Her epistemic progress is real, but the world contains nothing non-physical.
- Strongest objection
- If phenomenal concepts pick out physical states, critics ask why they reveal those states so differently, and so mysteriously, from all our other concepts. The explanation of phenomenal concepts may face its own hard problem.
- Defended by
- Brian Loar, David Papineau
IV
Mary learns nothing
If Mary really knew every physical fact, she would not be surprised. We cannot imagine what complete physical knowledge would be like.
- Best argument
- Daniel Dennett argued that our intuition that Mary learns something comes from imagining a Mary who knows a lot, not one who knows everything. A truly omniscient physical scientist would be able to work out exactly what red would look like, and would recognise it at once. If you tried to trick her with a banana painted blue, she would spot the trick at once, because she would know that what she was seeing was blue.
- Strongest objection
- Most people find it hard to believe that any amount of reading could tell you what red looks like. Dennett's response seems to deny the very premise the thought experiment rests on.
- Defended by
- Daniel Dennett, Paul Churchland
For the full background, variations and open questions, read the entry: Mary's room.