Philosopher Daniel Dennett takes as his purpose in Consciousness Explained the task of characterizing consciousness in terms of physical events in the brain that are not conscious. This, Dennett admits, is counterintuitive, for though consciousness may well be “supported by” or “connected to” the brain, consciousness itself seems fundamentally distinct from (mere) physical processes. How those processes actually can be one’s sensation of intense grief or one’s experience of a too-sour orange is the burden of his exposition. Part of the difficulty Dennett faces is in overcoming the heritage of René Descartes (1596-1650), whose Meditations (1641) helped establish in popular sentiment the notion of the dualism of mind and body. For Descartes, mind was a kind of “stuff” altogether different from physical matter but every bit as real. The brain could be studied empirically because it was subject to physical laws, but mind by definition was outside the reach of the physical sciences. The difference between the content of one’s conscious experience, the sense of what it is like to be oneself, and the firing of synapses in the brain seemed absolute. Dennett rejects Cartesian dualism in part because of its difficulty of explaining coherently how a nonphysical mind could affect, and in turn be affected by, a physical body, but also because dualism is resistant to empirical investigation.
Such investigation must be from the “third-person” point of view, he says, and so the “data” of one’s inner experience must be made publicly available in a way that does not already presume a particular theory of the mind. In the first part of Consciousness Explained Dennett develops a method (he dubs it heterophenomenology) by which a subject’s description of the phenomena of his or her “inner life” (the intentionality or “aboutness” of conscious experience) becomes a text which in effect constitutes a kind of fictional world—fictional because the subject can only report what it seems like, say to make an important decision, not what is actually going on inside the person: that actuality is unavailable to introspection but is the proper study of the empirical theorist. This distinction is crucial to Dennett’s own theory, which he develops in the second section of the book.
Dennett calls his model of consciousness the Multiple Drafts theory, arguing that “all varieties of perception—indeed, all varieties of thought or mental activity—are accomplished in the brain by parallel, multitrack processes of interpretation and elaboration of sensory inputs. Information entering the nervous system is under continuous ‘editorial revision.’” There is no single spot in the brain where consciousness “happens”; once one part of the brain has made a certain discrimination (of movement, say, or color), that information is an available part of the eventual pastiche that is conscious experience.
Dennett is not content with banishing dualism; he is also determined to root out from prevailing materialist theories of the brain any notion of a “Cartesian Theater,” a central location where the brain must re-present each of its discriminations. That is false, says Dennett, for such a notion would require a further explanation of how the “audience” in the Theater—called a “homunculus” or “little person” by philosophers—was itself conscious of the events on display. If the “explanation” involved positing another “theater” in the brain of the homunculus, and so on, clearly the question of the nature of consciousness would simply be forever deferred. According to Dennett, this brand of materialism is no better than Cartesian dualism; and though few if any cognitive scientists and philosophers would call themselves Cartesian materialists, the author is convinced the influence of Descartes continues to muddy the theoretical waters.
Perhaps the most appropriate metaphor for Dennett’s Multiple Drafts theory is that of a word processor. Any computer hardware running a particular word processing program in effect becomes a “virtual machine” for that program, responding as if the hardware had been designed just for running that program. Diverse computers—even large parallel processing units—that run the same program become the same virtual machine. The word processing program may seem relatively straightforward, with one event happening after another in serial order, but “in reality” many calculations are coming from various subsystems of the computer to be integrated...
(The entire section is 1884 words.)