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According to the knowledge argument, physicalism fails because when physically omniscient Mary first sees red, her gain in phenomenal knowledge involves a gain in factual knowledge. Thus not all facts are physical facts. According to the ability hypothesis, the knowledge argument fails because Mary only acquires abilities to imagine, remember and recognise redness, and not new factual knowledge. I argue that reducing Mary’s new knowledge to abilities does not affect the issue of whether she also learns factually: I show that gaining specific new phenomenal knowledge is required for acquiring abilities of the relevant kind. Phenomenal knowledge being basic to abilities, and not vice versa, it is left an open question whether someone who acquires such abilities also learns something factual. The answer depends on whether the new phenomenal knowledge involved is factual. But this is the same question we wanted to settle when first considering the knowledge argument. The ability hypothesis, therefore, has offered us no dialectical progress with the knowledge argument, and is best forgotten.

What is the nature of consciousness? How is consciousness related to brain processes? This volume collects thirteen new papers on these topics: twelve by leading and respected philosophers and one by a leading color-vision scientist. All focus on consciousness in the "phenomenal" sense: on what it's like to have an experience. Consciousness has long been regarded as the biggest stumbling block for physicalism, the view that the mind is physical. The controversy has gained focus over the last few decades, and phenomenal knowledge and phenomenal concepts--knowledge of consciousness and the associated concepts--have come to play increasingly prominent roles in this debate. Consider Frank Jackson's famous case of Mary, the super-scientist who learns all the physical information while confined in a black-and-white room. According to Jackson, if physicalism is true, then Mary's physical knowledge should allow her to deduce what it's like to see in color. Yet it seems intuitively clear that she learns something when she leaves the room. But then how can consciousness be physical? Arguably, whether this sort of reasoning is sound depends on how phenomenal concepts and phenomenal knowledge are construed. For example, some argue that the Mary case reveals something about phenomenal concepts but has no implications for the nature of consciousness itself. Are responses along these lines adequate? Or does the problem arise again at the level of phenomenal concepts? The papers in this volume engage with the latest developments in this debate. The authors' perspectives range widely. For example, Daniel Dennett argues that anti-physicalist arguments such as the knowledge argument are simply confused; David Papineau grants that such arguments at least reveal important features of phenomenal concepts; and David Chalmers defends the anti-physicalist arguments, arguing that the "phenomenal concept strategy" cannot succeed.

I argue for the superiority of non-gappy physicalism over gappy physicalism. While physicalists are united in denying an ontological gap between the phenomenal and the physical, the gappy affirm and the non-gappy deny a relevant epistemological gap. Central to my arguments will be contemplation of Swamp Mary, a being physically intrinsically similar to post-release Mary (a physically omniscient being who has experienced red) but has not herself (the Swamp being) experienced red. Swamp Mary has phenomenal knowledge of a phenomenal character not instantiated by any of her past or current mental states. I issue a challenge to gappy physicalists to account for how it is that Swamp Mary can satisfy the psychosemantic requirements on phenomenal knowledge while non-Swamp pre-release Mary cannot. I argue that gappy physicalists cannot meet this psychosemantic challenge.

Certain conceivable situations figure as premises in arguments for the conclusion that conscious experiences have nonphysical properties or qualia. Frank Jackson's knowledge argument considers the hypothetical scientist Mary, who despite having complete scientific knowledge of colour vision, supposedly lacks knowledge of qualia. Both Saul Kripke's and David Chalmers' modal arguments involve zombies, conceivable creatures physically identical to us who lack qualia. Several physicalists have replied to all these objections by endorsing the phenomenal concept reply. Without trying to undermine this reply in general, I argue that recent versions of it proposed by John Perry and David Papineau are unsatisfactory.

The book under review is a collection of thirteen essays on the nature phenomenal concepts and the ways in which phenomenal concepts figure in debates over physicalism. Phenomenal concepts are of special interest in a number of ways. First, they refer to phenomenal experiences, and the qualitative character of those experiences (aka “qualia”) whose metaphysical status is hotly debated. There are recent arguments, originating in Descartes’ famous conceivability argument, that purport to show that phenomenal experience is irreducibly non-physical. Second, phenomenal concepts are widely thought to be special and unique among concepts. Both the anti-physicalist arguments and physicalist replies to these arguments turn on views about the nature of phenomenal concepts. In this review I survey the many ways in which the essays in this volume are engaged (pro or con) with anti-physicalist arguments and the role phenomenal concepts play in these arguments.

One diagnosis of what is wrong with the Knowledge Argument rests on the Ability Hypothesis. This couples an ability analysis of knowing what an experience is like together with a denial that phenomenal propositions exist. I argue against both components. I consider three arguments against the existence of phenomenal propositions and find them wanting. Nevertheless I deny that knowing phenomenal propositions is part of knowing what an experience is like. I provide a hybrid account of knowing what an experience is like which is the coherent expression of a single idea: knowing what an experience is like is knowing what it would be like to have the phenomenal content of the experience as the content of an experience one is currently having. I explain how my conclusions indicate that the focus of discussion should be on the alleged explanatory gap between phenomenal facts and physical facts and not on the Knowledge Argument. The latter is a poor expression of the difficulty Physicalists face.

The knowledge argument aims to refute physicalism, the view that the world is entirely physical. The argument first establishes the existence of facts (or truths or information) about consciousness that are not a priori deducible from the complete physical truth, and then infers the falsity of physicalism from this lack of deducibility. Frank Jackson (1982, 1986) gave the argument its classic formulation. But now he rejects the argument (Jackson 1998b, 2003, chapter 3 of this volume). On his view, it relies on a false conception of sensory experience, which should be replaced with representationalism (also known as intentionalism), the view that phenomenal states are just representational states. And he argues that mental representation is physically explicable.

The central attempt of this paper is to explain the underlying intuitions of Frank Jackson’s “Knowledge Argument” that the epistemic gap between phenomenal knowledge and physical knowledge points towards a corresponding ontological gap. The first step of my analysis is the claim that qualia are epistemically special because the acquisition of the phenomenal concept of a quale x requires the experience of x. Arguing what is so special about phenomenal concepts and pointing at the inherence-relation with the qualia they pick out, I give compelling reasons for the existence of ontologically distinct entities. Finally I conclude that phenomenal knowledge is caused by phenomenal properties and the instantiation of these properties is a specific phenomenal fact, which can not be mediated by any form of descriptive information. So it will be shown that phenomenal knowledge must count as the possession of very special information necessarily couched in subjective, phenomenal conceptions.

It has long been widely agreed that some concepts can be possessed only by those who have undergone a certain type of phenomenal experience. Orthodoxy among contemporary philosophers of mind has it that these phenomenal concepts provide the key to understanding many disputes between physicalists and their opponents, and in particular offer an explanation of Mary’s predicament in the situation exploited by Frank Jackson's knowledge argument. I reject the orthodox view; I deny that there are phenomenal concepts. My arguments exploit the sort of considerations that are typically used to motivate externalism about mental content. Although physicalists often appeal to phenomenal concepts to defend their view against the knowledge argument, I argue that this is a mistake. The knowledge argument depends on phenomenal concepts; if there are no phenomenal concepts, then the knowledge argument fails.

Deviant phenomenal knowledge is knowing what it’s like to have experiences of, e.g., red without actually having had experiences of red. Such a knower is a deviant. Some physicalists have argued and some anti-physicalists have denied that the possibility of deviants undermines anti-physicalism and the Knowledge Argument. The current paper presents new arguments defending the deviant-based attacks on anti-physicalism. Central to my arguments are considerations concerning the psychosemantic underpinnings of deviant phenomenal knowledge. I argue that physicalists are in a superior position to account for the conditions in virtue of which states of deviants constitute representations of phenomenal facts.