Knowledge argument (Mary's Room)
Explanation
Frank Jackson devised in 1982 one of the most discussed thought experiments in contemporary philosophy: Mary's Room. Mary is a brilliant scientist who has lived all her life in a black-and-white room. She has access to all possible physical information about colour perception: she knows all the wavelengths, all the photoreceptors, all the neural pathways, everything the sciences could explain about what happens when someone sees red.
One day the door is opened and Mary sees a red rose for the first time. The crucial question: does she learn anything new? The overwhelming intuition is yes: she discovers what it is like to see red, the phenomenal quality of colour. But she already knew everything physical. So what she learns must not have been part of the physical information. Therefore consciousness includes non-physical facts.
The argument is a form of epistemic dualism: even if metaphysical physicalism were true, our knowledge cannot be exhausted by physical descriptions; there are aspects of reality (qualia) only known from within. Jackson himself would later abandon dualism, but the argument took on a life of its own.
Physicalist responses are varied. The new ability hypothesis holds that Mary does not learn a new fact, she only acquires a skill (recognising, imagining, recalling red). The new mode of presentation hypothesis holds that Mary already knew the same physical fact, but now knows it in another way, from a first-person perspective, without there being two kinds of facts.
Daniel Dennett replies with his usual irony: if Mary really knew all the physical facts, she would know what response she would have on seeing a rose, and would not be surprised. For Dennett, the argument cheats: it underestimates how much physical knowledge everything would be. It is a kind of contaminated intuition pump, making us feel something is missing without really justifying why anything would be.
Thirty years of debate have not closed the question. Mary's thought experiment remains a philosophical Rorschach test: those inclined towards inflationism see it as definitive proof of irreducible qualia; those inclined towards deflationism see it as a persuasive but misleading cognitive illusion. Consciousness, once again, proves to be the least stable of philosophical topics.
Strengths
- Memorable and accessible beyond the philosophical circle.
- Articulates the intuition of the 'explanatory gap' between the physical and the experiential.
- Catalyst for discussions on kinds of knowledge.
- Reinforces Chalmers's hard problem.
Main critiques
- Ability-knowledge reply (Lewis, Nemirow): Mary acquires a capacity, not facts.
- Acquaintance-knowledge reply: a new way of knowing an old fact.
- Jackson himself abandoned the argument in favour of a posteriori physicalism.
- Depends on intuitions that may be empirically revisable.