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Consciousness is more familiar to us than any other feature of our world, since it is the route by which anything at all becomes familiar. But this is what makes consciousness so hard to pinpoint. Look for it wherever you like, you encounter only its objects – a face, a dream, a memory, a color, a pain, a melody, a problem, but nowhere the consciousness that shines on them. Trying to grasp it is like trying to observe your own observing, as though you were to look with your own eyes at your own eyes without using a mirror. Not surprisingly, therefore, the thought of consciousness gives rise to peculiar metaphysical anxieties, which we try to allay with images of the soul, the mind, the self, the “subject of consciousness,” the inner entity that thinks and sees and feels and that is the real me inside. But these traditional “solutions” merely duplicate the problem. We cast no light on the consciousness of a human being simply by redescribing it as the consciousness of some inner homunculus – be it a soul, a mind, or a self. On the contrary, by placing that homunculus in some private, inaccessible, and possibly immaterial realm, we merely compound the mystery.

Putting the point in that way makes it clear that, in the first instance at least, the problem of consciousness is a philosophical, not a scientific, problem. It cannot be solved by studying the empirical data, since consciousness (as normally understood) isn’t one of them. We can observe brain processes, neurons, ganglions, synapses, and all the other intricate matter of the brain, but we cannot observe consciousness. I can observe you observing, but what I observe is not that peculiar thing that you know from within and that is present, in some sense, only to you. At least, so it would seem; if this is some kind of mistake, it is a philosophical and not a scientific argument that will tell us so.

This appropriation of the question by philosophy is apt to make scientists impatient. Surely, they will argue, if consciousness is real it must be part of the real world – the world of space and time, which we observe with our senses and explain by science. But what part? First-person reports of conscious states are radically affected by brain damage, and the behavior that leads us to describe others as conscious originates in the nervous system, whose functions seem to be largely controlled by the brain. Common sense and scientific inference therefore both point to the brain as the seat of consciousness. So, scientists argue, let’s study the brain and find out exactly which of its processes correspond to our conscious mental states. That way, they suggest, we will find out what consciousness is.

But will we? Unfortunately, the philosophical problem comes back at us in another form. How exactly do we discover a correspondence between consciousness and a brain process, given that consciousness is not something that we observe? And suppose we overcome that difficulty and produce a theory correlating conscious mental states with specific neurological events. This means that we have discovered what consciousness is only if we can advance from correspondence to identity. And that is precisely what so many philosophers doubt we can do. True, there are some who defend the view that conscious states are identical with brain processes, but they defend it on philosophical, not scientific, grounds. And their view is open to radical objections: for example, how can a state of one thing (a person) be identical with a process in another (a brain)?

If the neurobiologist Christof Koch, professor of cognitive and behavioral biology at Caltech, enters this territory with some trepidation, he nevertheless hopes to take possession of it in the name of science. The task, he believes, is to avoid getting lost in definitions and conceptual puzzles and instead to discover the “neuronal correlates of consciousness.” He at once narrows that target, however, to “the minimal set of neuronal events and mechanisms jointly sufficient for a specific conscious percept.” In other words, the object of study is not consciousness as such but “specific conscious percepts,” in particular those involved in visual perception. Koch’s ambition, nevertheless, is to integrate the analysis of vision into the more general program that he developed with the late Francis Crick, one of the discoverers of the structure of DNA, who contributes the foreword to the book. That program is to explain how consciousness evolved and identify the processes in the brain that carry it. The book gives a fairly comprehensive account of what neurobiology has to say about the higher functions of the brain. It is not surprising, therefore, that the writing is densely scientific and heavily referenced, with many digressions. But proceeding on the supposition that the science is correct, what do we make of the title? Does neurobiology in the style of Crick and Koch really take us further in the “quest for consciousness”? Or is it simply amassing more and more information about the brain, without telling us how brain and mind are connected?

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