D. Chalmers

It's very interesting to see neurophysiological evidence brought to bear on the puzzling question of conscious experience. Many have observed that information-processing models of cognition seem to leave consciousness untouched; it is natural to hope that turning to neurophysiology might lead us to the Holy Grail. Still, I think there are reasons to be skeptical. There are good reasons to suppose that neurophysiological investigation contributes to cognitive explanation at best in virtue of constraining the information-processing structure of cognition. Of course this is a very large and significant role for it to play, but it may be over-optimistic to suppose that it can play some further explanatory role, taking us where information-processing theories cannot. If so, then neurophysiological accounts will be no more and no less successful at dealing with consciousness than information-processing accounts are.

Why is two-dimensional semantics important? One can think of it as the most recent act in a drama involving three of the central concepts of philosophy: meaning, reason, and modality. First, Kant linked reason and modality, by suggesting that what is necessary is knowable a priori, and vice versa. Second, Frege linked reason and meaning, by proposing an aspect of meaning (sense) that is constitutively tied to cognitive signi?cance. Third, Carnap linked meaning and modality, by proposing an aspect of meaning (intension) that is constitutively tied to possibility and necessity

A number of popular arguments for dualism start from a premise about an epistemic gap between physical truths about truths about consciousness, and infer an ontological gap between physical processes and consciousness. Arguments of this sort include the conceivability argument, the knowledge argument, the explanatory-gap argument, and the property dualism argument. Such arguments are often resisted on the grounds that epistemic premises do not entail ontological conclusion. My view is that one can legitimately infer ontological conclusions from epistemic premises, if one is very careful about how one reasons. To do so, the best way is to reason first from epistemic premises to modal conclusions (about necessity and possibility), and from there to ontological conclusions. Here, the crucial issue is the link between the epistemic and modal domains. How can one reason from theses about what is knowable or conceivable to theses about what is necessary or possible? To bridge the epistemic and modal domains, the framework of two-dimensional semantics can play a central role. I have used this framework in earlier work (Chalmers 1996) to mount an argument against materialism. Here, I want to revisit the argument, laying it out in a more explicit and careful form, and responding to a number of objections. In what follows I will concentrate mostly on the conceivability argument. I think that very similar considerations apply to the other arguments mentioned above, however. In the final section of the paper, I show how this analysis might yield a unified treatment of a number of anti-materialist arguments

Consciousness and intentionality are perhaps the two central phenomena in the philosophy of mind. Human beings are conscious beings: there is something it is like to be us. Human beings are intentional beings: we represent what is going on in the world.Correspondingly, our specific mental states, such as perceptions and thoughts, very often have a phenomenal character: there is something it is like to be in them. And these mental states very often have intentional content: they serve to represent the world. On the face of it, consciousness and intentionality are intimately connected. Our most important conscious mental states are intentional states: conscious experiences often inform us about the state of the world. And our most important intentional mental states are conscious states: there is often something it is like to represent the external world. It is natural to think that a satisfactory account of consciousness must respect its intentional structure, and that a satisfactory account of intentionality must respect its phenomenological character.With this in mind, it is surprising that in the last few decades, the philosophical study of consciousness and intentionality has often proceeded in two independent streams. This wasnot always the case. In the work of philosophers from Descartes and Locke to Brentano and Husserl, consciousness and intentionality were typically analyzed in a single package. But in the second half of the twentieth century, the dominant tendency was to concentrate on onetopic or the other, and to offer quite separate analyses of the two. On this approach, the connections between consciousness and intentionality receded into the background.In the last few years, this has begun to change. The interface between consciousness and intentionality has received increasing attention on a number of fronts. This attention has focused on such topics as the representational content of perceptual experience, the higherorder representation of conscious states, and the phenomenology of thinking. Two distinct philosophical groups have begun to emerge. One group focuses on ways in which consciousness might be grounded in intentionality. The other group focuses on ways in which intentionality might be grounded in consciousness

How does conscious experience emerge from a physical basis? At a first glance, this is the question about the mind that most needs answering. So it is curious that those who study the mind professionally have often avoided the question entirely. In psychology, the cognitive revolution did not make consciousness respectable: most cognitive psychologists have stuck to subjects such as learning, memory, and perception instead. Neuroscientists have been known to speculate on the topic, but usually only late at night, after a few drinks. Even philosophers have been curiously diffident. Some have been exercised by the fact that there is a problem, others have been concerned to deny the problem entirely, but the focus of inquiry has remained elsewhere. As in all these fields, serious theories of consciousness have been hard to come by.

More than a decade ago, philosopher John Searle started a long-running controversy with his paper “Minds, Brains, and Programs” (Searle, 1980a), an attack on the ambitious claims of artificial intelligence (AI). With his now famous _Chinese Room_ argument, Searle claimed to show that despite the best efforts of AI researchers, a computer could never recreate such vital properties of human mentality as intentionality, subjectivity, and understanding. The AI research program is based on the underlying assumption that all important aspects of human cognition may in principle be captured in a computational model. This assumption stems from the belief that beyond a certain level, implementational details are irrelevant to cognition. According to this belief, neurons, and biological wetware in general, have no preferred status as the substrate for a mind. As it happens, the best examples of minds we have at present have arisen from a carbon-based substrate, but this is due to constraints of evolution and possibly historical accidents, rather than to an absolute metaphysical necessity. As a result of this belief, many cognitive scientists have chosen to focus not on the biological substrate of the mind, but instead on the abstract causal structure_ _that the mind embodies (at an appropriate level of abstraction). The view that it is abstract causal structure that is essential to mentality has been an implicit assumption of the AI research program since Turing (1950), but was first articulated explicitly, in various forms, by Putnam (1960), Armstrong (1970) and Lewis (1970), and has become known as _functionalism_. From here, it is a very short step to _computationalism_, the view that computational structure is what is important in capturing the essence of mentality. This step follows from a belief that any abstract causal structure can be captured computationally: a belief made plausible by the Church–Turing Thesis, which articulates the power

Is there progress in philosophy? A What might be called a glass-half-full view of philosophical progress is that there is some progress in philosophy. The glass-half-empty view is that there is not as much as we would like. Inspired in part by van Inwagen’s discussion of disagreement in philosophy, this paper articulates and argues for a thesis about the relative lack of progress in philosophy: there has been less convergence to the truth on the big questions of philosophy than on the big questions of the hard sciences. It then investigates the question of what explains this relative lack of progress. The paper considers a number of explanations and argues that none of them is fully adequate. It then articulates a form that an adequate explanation might take.

Consciousness fits uneasily into our conception of the natural world. On the most common conception of nature, the natural world is the physical world. But on the most common conception of consciousness, it is not easy to see how it could be part of the physical world. So it seems that to find a place for consciousness within the natural order, we must either revise our conception of consciousness, or revise our conception of nature. In twentieth-century philosophy, this dilemma is posed most acutely in C. D. Broad’s The Mind and its Place in Nature (1925). The phenomena of mind, for Broad, are the phenomena of consciousness. The central problem is that of locating mind with respect to the physical world. Broad’s exhaustive discussion of the problem culminates in a taxonomy of seventeen different views of the mental-physical relation.1 On Broad’s taxonomy, a view might see the mental as nonexistent (“delusive”), as reducible, as emergent, or as a basic property of a substance (a “differentiating” attribute). The physical might be seen in one of the same four ways. So a four-by-four matrix of views results. (The seventeenth entry arises from Broad’s division of the substance/substance view according to whether one substance or two is involved.) At the end, three views are left standing: those on which mentality is an emergent characteristic of either a physical substance or a neutral substance, where in the latter case, the physical might be either emergent or delusive

First, I should clarify the notion of "taking consciousness seriously", which serves as a premise in my work. Mulhauser characterizes this as the assumption that no cognitive theory of consciousness will suffice. The latter assumption would indeed beg some crucial questions, but it is not the assumption that I make. I make an assumption about the problem of consciousness, not about any solution. To quote (p. xii): Throughout the book, I have assumed that consciousness exists, and that to redefine the problem as that of explaining how certain cognitive and behavioral functions are performed is unacceptable. This is what I mean by taking consciousness seriously. That is, the premise is simply that there is a phenomenon to be explained, and that the problems of explaining such functions as discrimination, integration, self monitoring, reportability, and so on do not exhaust all the problems in the vicinity. The deepest problem of consciousness, as I understand it, is not the problem of how all these functions are performed, but rather the problem of explaining how and why all this activity supports states of subjective experience.