David Chalmers:
"The Character of Consciousness" (Oxford University Press, 2010)

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The Australian philosopher David Chalmers published one of the most important books in the resurgent field of Philosophy of Mind: "The Conscious Mind" (1996). That book separated the study of cognition from the study of consciousness, pushing cognition into the "body" part of the body-mind debate. It also introduced Chalmers' claim that a science of consciousness is possible, but it will be something very different from Physics. Chalmers offered a rigorous proof that consciousness cannot be reduced to the physical. Consciousness is a fundamental feature of this universe. There might be a way to explain consciousness, but it takes a whole different (non-reductive) approach. He made the analogy with electromagnetism. Electromagnetism could not be explained by "reducing" electromagnetic phenomena to the known properties of matter: it was explained when scientists introduced a whole new set of properties (and related laws), the properties of microscopic matter that yield the macroscopic phenomenon of electromagnetism. By the same token, consciousness cannot be explained by the physical laws of the known properties of matter but requires a new set of "psychophysical" laws. And the explanation is likely to be "correlative" rather than "reductive".

The new book expands and refines those ideas. The first seven chapters are roughly a reexposition of those ideas. Neuroscience can explain the processes that originate conscious experience (Nagel's "what it is like to be"), but cannot explain the conscious experience itself. In fact, there is nothing in those processes that would lead an observer to conclude "ah ah here there is a conscious experience". Those processes simply prescribe how inputs affect the structure of the brain and yield some outputs. There is a systematic correlation between those processes and conscious experience, but one cannot be reduced to the other. Chalmers believes that science needs to expand its ontology the same way that Physics had to expand its ontology in order to accommodate a theory of electromagnetism (which cannot be reduced to, say, gravitation). The required expansion is one that would recognize conscious experience as fundamental. Chalmers has made some controversial claims as to which principles preside on this fundamental feature. For example, he believes (unlike Searle) that conscious experience is related to the organization of the brain and not to its substance, i.e. that one could in theory build a conscious machine. Chalmers relates this expanded ontology to his concept of "information", which is really two things in one: a physical aspect and a phenomenal aspect.

Chapter five contains his arguments against Materialism, notably against Daniel Dennett's highly deflationary materialism (that Chalmers renames "Type-A Materialism"). Chalmers finds that there are three theories of mind that fit the data: Descartes' substance dualism ("Type-D Dualism"), which seems to be consistent with a popular interpretation of Quantum Mechanics (that the conscious observer causes the "collapse" of the quantum wave into the real world, loosely related to panpsychism); "Type-F Monism" (Chalmers' new term for Russell's monism), according to which consciousness arises from properties of fundamental physical entities; and epiphenomalism ("Type-E dualism"), according to which consciousness is just an accidental by-product of physical processes with no power on physical processes.

Chapter eight deals with phenomenal concepts, i.e. concepts that are commonly employed to discuss consciousness.

Chapters 11-12 deal with the relationship between consciousness (i.e., phenomenology) and (philosophical) intentionality: conscious beings are capable of representing the world. Chalmers argues that intentionality is as fundamental as consciousness, and therefore one cannot be reduced to the other. They are both fundamental, and tightly coupled, although he doesn't get very specific (either they are the same thing, and then why bother, or they are not, in which case there must be some cases in which one is and the other one is not).

Chalmers make a distinction between "Russellian content", that uses objects and properties to represent the world, and "Fregean content", that uses sense and referent to represent the world. By extending Frege's intension to primary intension ("modes of presentation"), Chalmers argues that some problems with representationalism can be resolved. In particular, representationalism based on Fregean content is nonreductive. This choice lays the foundation for Chalmer's version of two-dimensional semantics (one semantic value is associated with reference, while the other is associated with the way that reference depends on the external world).

Chapter 12 investigates how the world is captured in the phenomenology of conscious experience. Chalmers does this by introducing the "phenomenal content", which turns out to be a kind of Fregean content. Chalmers proposes a two-stage Fregean model for all sorts of sensory experiences. Fregean content, however, is not enough to account for the whole spectrum of perceptual content, and Chalmers has to introduce another tool, that of "Edenic" content (the world we perceive is the world as it is), which constitutes the very foundation of perception. However, Chalmers' analyses of perceptual contents is not clear at all, despite being littered with all sorts of technicalities. By definition, the phenomenal content of conscious experience is Edenic...

Chapter 13 uses the movie "The Matrix" to speculate about a conscious being's knowledge of the real world. Chalmers uses two fundamental an antithetic concepts: "Eden" is the world as we perceive it (Kant's phenomenal world), whereas the "Matrix" represents the non-intuitive world that science is unveiling to us (Kant's noumenal world). People who live in Eden have nothing to worry about: the world is exactly the way they perceive it. People who live in the Matrix, instead, have to worry about the real nature of the world that is hidden from their senses. Chalmers disputes the common-sense theory that the brain living inside the matrix is living in an "unreal" world. Basically, it doesn't matter whether your brain is inside a matrix (a simulation) or not. We have no idea what reality is like. Reality could just be a fuzzy cloud of elementary particles. None of the objects we see is real. All we know is the reality that our brains create for us. The brain takes some inputs, presumably from the real world, and it then shows me a world made of colored, noisy, scented objects and people. The real world is perpetually unknown to me. Quantum Mechanics, for example, tells us that the real world is wildly different from the world of objects that we perceive. We cannot perceive the real world described by Quantum Mechanics, just like the brain in the Matrix cannot perceive that it is living inside a simulation. Another way to put it is: a brain is a computer that runs a program, and your life is the output of that program, and it is irrelevant from where the inputs originate because they are external to you anyway. Whether you truly have a body or not, and whether your body truly did what you think it did, makes no difference. As Chalmers puts it: "This is simply the condition of a creature living in a world".

The final chapter tackles the unity of consciousness. At any point in time we experience a multiplicity of conscious experience: we see, we hear, we smell, etc. This is another lengthy chapter that remains quite vague. Chalmers seems to lean towards the idea that consciousness is fundamentally a whole, but then it sounds like it can be separated into parts.

This colossal book is an unfinished work, and it might have been better to wait a few more years before committing it to the printing press. "The Conscious Mind" remains Chalmers' classic, a book that has not aged at all and that is easier to read than this ambitious follow-up.

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