The problem of consciousness remains with us. What exactly is it and why is it still with us? The single most important question is: How exactly do neurobiological processes in the brain cause human and animal consciousness? Related problems are: How exactly is consciousness realized in the brain? That is, where is it and how does it exist in the brain? Also, how does it function causally in our behavior?
To answer these questions we have to ask: What is it? Without attempting an elaborate definition, we can say the central feature of consciousness is that for any conscious state there is something that it feels like to be in that state, some qualitative character to the state. For example, the qualitative character of drinking beer is different from that of listening to music or thinking about your income tax. This qualitative character is subjective in that it only exists as experienced by a human or animal subject. It has a subjective or first-person existence (or “ontology”), unlike mountains, molecules, and tectonic plates that have an objective or third-person existence. Furthermore, qualitative subjectivity always comes to us as part of a unified conscious field. At any moment you do not just experience the sound of the music and the taste of the beer, but you have both as part of a single, unified conscious field, a subjective awareness of the total conscious experience. So the feature we are trying to explain is qualitative, unified subjectivity.
Now it might seem that is a fairly well-defined scientific task: just figure out how the brain does it. In the end I think that is the right attitude to have. But our peculiar history makes it difficult to have exactly that attitude—to take consciousness as a biological phenomenon like digestion or photosynthesis, and figure out how exactly it works as a biological phenomenon. Two philosophical obstacles cast a shadow over the whole subject. The first is the tradition of God, the soul, and immortality. Consciousness is not a part of the ordinary biological world of digestion and photosynthesis: it is part of a spiritual world. It is sometimes thought to be a property of the soul and the soul is definitely not a part of the physical world. The other tradition, almost as misleading, is a certain conception of Science with a capital “S.” Science is said to be “reductionist” and “materialist,” and so construed there is no room for consciousness in Science. If it really exists, consciousness must really be something else. It must be reducible to something else, such as neuron firings, computer programs running in the brain, or dispositions to behavior.
There are also a number of purely technical difficulties to neurobiological research. The brain is an extremely complicated mechanism with about a hundred billion neurons in humans, and most investigative techniques are, as…
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