A Physicalist Interpretation of Phenomenal Knowledge — Epoche B2
What Mary Didn't Know, and Why Jackson Changed His Mind Setting the question correctly Frank Jackson's knowledge argument is usually taught as an open challenge to physicalism [1] , to be met by finding a flaw in one of its premises. That framing has a defect worth stating at the outset: Jackson himself gave the argument up [2] . He announced the reversal in a postscript in 1998 and defended it at length in "Mind and Illusion" (2003). So an essay arguing that the argument fails is not arguing against Jackson [3] . The question worth asking is which objection defeats it, and here the standard teaching gives poor guidance, because the reason Jackson gave is not one of the standard replies. This essay argues two things. First, the two leading physicalist responses — the Ability Hypothesis and the phenomenal-concept strategy — are usually presented together and are in fact incompatible [4] ; a physicalist must choose, and each choice has a cost. Second, the objection that does the damage attacks neither premise but the argument's conclusion: epiphenomenal qualia cannot be what our beliefs about qualia are about, so the argument undermines the very knowledge it claims Mary acquires. That was Jackson's reason, and it is stronger than the others because it requires no theory of concepts. The argument In "Epiphenomenal Qualia" (1982), Jackson asks us to imagine Mary, a scientist who has spent her life in a black-and-white room and has learned every physical fact about colour vision: the optics, the wavelengths, the retinal chemistry, the neural processing, the behavioural dispositions. Then she leaves the room and sees something red. Jackson's claim is that she learns something. If she learns something, there was a fact she did not know. But she knew all the physical facts. So there are non-physical facts, and physicalism is false. Jackson accepted the natural consequence: if the phenomenal facts are non-physical and the physical world is causally closed, then phenomenal properties do no causal work. He embraced epiphenomenalism, which is what the paper's title announces, and devoted part of the paper to defending it. Two clarifications matter. The argument is not about what Mary can imagine; it is about what she knows. And it does not depend on Mary being possible in practice. It depends only on the claim that complete physical knowledge would leave something out. Two physicalist replies that cannot both be right The Ability Hypothesis , developed by Laurence Nemirow and by David Lewis in "What Experience Teaches" (1988 [5] ), denies that Mary learns any fact. What she gains is know-how: the abilities to imagine red, to recognise it when she sees it again, and to remember it. Knowing how to ride a bicycle is not knowing a proposition about bicycles, and on this view knowing what it is like is the same sort of thing. Since no new fact is learned, no non-physical fact is learned, and the argument fails at its second step. The phenomenal-concept strategy , associated above all with Brian Loar's "Phenomenal States" (1990), says the opposite. Mary does learn something propositional. What she acquires is a new concept — a recognitional concept formed on the basis of experience — which picks out a property she already knew about under a physical description. The fact is old; the mode of presentation is new. The analogy is with learning that the substance called water is H₂O: one fact, two ways of thinking about it. These are not two halves of one answer. They give contradictory verdicts on whether Mary acquires new propositional knowledge. Textbooks that list them as complementary physicalist options obscure a real fork. Each fork has a known cost. Against the Ability Hypothesis: Mary's new state has the marks of propositional attitude. She can be surprised; she can wonder in advance whether red will look like that ; she can be told something about it and disbelieve it. Abilities are not surprising and cannot be disbelieved. Against the phenomenal-concept strategy: David Chalmers's dilemma in "Phenomenal Concepts and the Explanatory Gap" (2007 [6] ). Whatever feature of phenomenal concepts is supposed to explain why Mary is in her epistemic situation is either physically explicable or not [7] . If it is, then a physical duplicate of Mary with no experiences would have concepts with that feature too, so the feature cannot explain a gap that arises from having experiences. If it is not, physicalism is false. Neither horn is comfortable. Jackson's reason Jackson did not defect to either camp. His objection is to the position he himself had adopted. The argument's conclusion is that qualia are non-physical and causally idle. But Mary's coming to know what red looks like is an event in the world. Her saying "so that is what it is like" is a physical event, produced by physical causes: photons, retina, cortex, motor output. If qualia are epiphenomenal, they are not among those causes. Her utterance would have been exactly the same had there been no quale at all. The same holds for her belief, and for Jackson's own belief that the knowledge argument is sound. This is not merely uncomfortable. It removes the argument's evidence. The argument's first premise is that Mary learns something, and our warrant for that premise is our conviction about what our own experiences are like. But if the experiences play no part in producing the conviction, the conviction is not tracking them. Something else — the physical machinery — produces it, and would have produced it anyway. A belief about X that is entirely caused by factors independent of X is not knowledge of X, whatever else it is. So the argument, if sound, gives us reason to doubt the premise it starts from. Jackson's own resolution was to adopt representationalism, on which the phenomenal character of an experience consists in what the experience represents about the world, so that Mary gains a new way of representing physical properties and nothing non-physica