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According to Frank Jackson’s famous knowledge argument, Mary, a brilliant neuroscientist raised in a black and white room and bestowed with complete physical knowledge, cannot know certain truths about phenomenal experience. This claim about knowledge, in turn, implies that physicalism is false. I argue that the knowledge argument founders on a dilemma. Either (i) Mary cannot know the relevant experiential truths because of trivial obstacles that have no bearing on the truth of physicalism or (ii) once the obstacles have been removed, Mary can know the relevant truths. If we give Mary the epistemological capabilities necessary to draw metaphysical conclusions about physicalism, she will, while trapped in the black and white room, be able to know every truth about phenomenal experience.

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.

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.

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.

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.

Over the past decade or so, David Papineau has given an account of the content and motivation of a physicalist conception of the world with more thoroughness and argumentative defence than many physicalists have thought necessary. In doing this, he has substantially advanced the debate on physicalism, and physicalists and non-physicalists alike should be grateful to him.1 At the heart of Papineau’s defence of physicalism in his recent book (2002) is his theory of phenomenal concepts. Like many physicalists, Papineau diagnoses the apparent threats to physicalism posed by the phenomena of consciousness by locating the source of anti-physicalist intuitions in features of our thinking rather than in non-physical features of reality. But what is new in Thinking About Consciousness is his detailed account of which features of our thinking it is that generate these supposedly confused anti-physicalist arguments. Hence the bulk of the book is an attempt to show that the most famous ‘consciousness-based’ anti-physicalist arguments—the knowledge argument, the zombie argument and the explanatory gap argument—rest on a mistaken understanding of certain kinds of concepts: phenomenal concepts. I agree with Papineau that physicalism (properly understood) should not be troubled by the knowledge argument and the explanatory gap argument, and that some other anti-physicalist arguments seem to move from assumptions about ways of thinking to conclusions about reality. But I doubt whether his theory of phenomenal concepts can help his defence of physicalism and his diagnosis of the errors of dualism. My reason for saying this is that I do not think there are any such concepts. In saying this I do not mean to deny that there is a useful distinction to be made between scientific concepts, the mastery of which requires knowledge of a certain amount of theory, and concepts which are acquired on the basis of experience, which can be called ‘phenomenal’ concepts.

Phenomenal knowledge usually comes from experience. But it need not. For example, one could know what it’s like to see red without seeing red—indeed, without having any color experiences. Daniel Dennett (2007) and Pete Mandik (forthcoming) argue that this and related considerations undermine the knowledge argument against physicalism. If they are right, then this is not only a problem for anti‐physicalists. Their argument threatens to undermine any version of phenomenal realism—the view that there are phenomenal properties, or qualia, that are not conceptually reducible to physical or functional properties. I will argue that this threat is illusory. Explaining why will clarify what is and is not at issue in discussions of the knowledge argument and phenomenal realism. This will strengthen the case for physically and functionally irreducible qualia.

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.