Experiment #1 · Thought experiment

Mary's Room

The Knowledge Argument

Frank Jackson · 1982 · Philosophy of mind

First published: Frank Jackson, "Epiphenomenal Qualia", *Philosophical Quarterly* 32 (1982): 127–136.

A complete physical description of colour vision still leaves something out — or does it?

Mary is a brilliant neuroscientist who has lived her entire life in a black-and-white room, learning everything physical there is to know about colour vision from books and monitors. One day she leaves the room and sees a red tomato for the first time. The question is whether she learns a new fact upon seeing red. If she does, then physicalism — the thesis that all facts are physical facts — is false, since Mary already knew every physical fact. If she does not, the qualitative character of experience reduces to physical information and physicalism survives. The experiment has become the canonical test case for the irreducibility of phenomenal consciousness.

Formulation

(1) Mary knows every physical fact about colour vision before leaving the room. (2) On seeing red, Mary learns something new. Therefore (3) not every fact is a physical fact. — Jackson originally endorsed (1)–(3) and the dualist conclusion, but recanted in 1998 in favour of a representationalist physicalism.

Compare this experiment

Dimensions Engaged

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Observer

Bears directly on Observer · Knowledge Extent and Observer · Physicality. If qualia are a separate kind of knowledge, the observer is not exhausted by its physical substrate; if not, the observer is fully describable in third-person terms.

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Matter

Tests whether the physical inventory of the world is complete (Matter · Ontological Status). A dualist verdict forces matter to be one ontological category among others; a physicalist verdict keeps matter sufficient.

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Information

Asks whether all facts are propositional/informational. If "knowing what red is like" is non-propositional knowledge, Information · Granularity admits non-discrete elements that no bit-string can capture.

Responses — How Schools Engage

Affirms / takes the bait 2

Dualism

The straightforward verdict: Mary learns a genuinely new fact (what red is like), so phenomenal properties are not physical. Jackson 1982 endorsed this; contemporary property dualists (Chalmers) continue to.

Panpsychism

Mary learns a new fact, and the right response is to expand the ontology rather than reject the intuition: phenomenal properties are fundamental and ubiquitous, not anomalous additions to a physical base.

Denies / rejects the premise 2

Naturalism

Mary gains no new *fact*, only a new mode of access to facts she already knew — the "ability hypothesis" (Nemirow, Lewis) treats knowing-what-red-is-like as a know-how, not a propositional addition. Physicalism is preserved.

Logical Positivism

If "what red is like" cannot be stated in observation language, the claim that Mary learns it adds no meaningful content — the apparent gain is verbal, not cognitive.

Reframes the question 2

Analytic Metaphysics / Logical Atomism

Following late Jackson and representationalists (Tye, Lycan): Mary learns no new fact, only a new first-person mode of presentation of the same physical fact. The intuition of novelty is granted; the dualist inference from it is denied.

Phenomenology

The thought experiment misdescribes its own starting point: Mary, as an embodied subject, was never in the pure third-person position the argument requires. The first-personal "what it is like" was already structurally prior to her physics textbooks.