In determining how many people of average weight could be carried on an airplane, engineers deal with abstractions. They ignore every aspect of actual, concrete human beings except their weight; indeed, they ignore even their actual weight, since it could turn out that no passenger weighs exactly whatever the average turns out to be. This is fine for the purposes at hand, though it would be ludicrous for those planning the flight entertainment or cabin meals to rely solely on the engineers' considerations.It would be even more ludicrous for them to insist that unless evidence of meal and movie preferences can be gleaned from the engineers' data, there just is no fact of the matter about what meals and movies actual human beings would prefer.
Science also deals with abstractions. The differences between a pebble, a poodle, and a planet are vast, but Newton's laws of motion largely ignore them, since most of the differences make no difference to how external forces alter an object's movement through space. Hence facts about poodle digestive systems and planetary atmosphere can be bracketed off and attention confined to mass, acceleration, and the like. Frictionless surfaces, centers of gravity, and other abstract objects are the stock in trade of the natural scientist. Unlike the engineer's abstractions, though, those of physics, chemistry, biology, and the other sciences are often treated as if they captured, not merely aspects of reality, but the whole of reality. This is "scientism"—the view that the scientific description of the world is an exhaustive description.
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Scientism is not itself a scientific thesis but a philosophical one. That it is therefore self-defeating is one well-known problem with the view. But its tendency to mistake abstractions for concrete reality—to commit what Alfred North Whitehead called the "Fallacy of Misplaced Concreteness" and what is also often called the "Reification Fallacy"—is no less problematic. Proponents of scientism often claim that if some purported feature of the world—free will, say, or consciousness—cannot be found in the description provided by physics, chemistry, neuroscience, etc., then it must not be real after all. This is like claiming that airline passengers have no meal or movie preferences, on the grounds that such preferences cannot be read off from the engineers' description of the passengers' average weight.
The fallacy is common in popular writing about science, and Michael Gazzaniga's Who's In Charge? Free Will and the Science of the Brain is, unfortunately, no exception. To be sure, Gazzaniga, an eminent professor of psychology at the University of California, Santa Barbara, resists the cruder forms of reductionism that figure in too many discussions of the implications of neuroscience. And reductionism is the usual consequence of the Reification Fallacy. Once you've concluded that what science tells us is real is all that is real, the next step is to insist that whatever phenomena seem to fall through science's net—our conscious thoughts and choices, for example—must, contrary to appearances, "really" be "nothing but" what the science textbooks make reference to, whether muscle activity, neural firing patterns, or whatever. If they exist at all, that is. For those beholden to scientism, the only alternative to reductionism is "eliminativism," the view that if some apparent feature of the world cannot be reduced to scientific categories, it should be eliminated altogether. Hence the willingness of some advocates of scientism seriously to entertain the suggestion that free will, consciousness, and thought might simply be illusions.
The trouble with Gazzaniga is that while he admirably resists such extreme conclusions, he is no less beholden than reductionists and eliminativists are to the fallacy that leads to them: the tendency to "reify" abstractions, i.e. to treat them as if they were concrete realities. (Albeit the abstractions in Gazzaniga's case—"modules" in the brain, an "interpreter" in the brain's left hemisphere, and the like—derive from neuroscience rather than physics.)
Not that he isn't in good company. This tendency has dominated theorizing about human nature since Rene Descartes, the father of modern philosophy and one of the fathers of modern science. Common sense tells us that a human being is by nature a thing that eats, sleeps, digests, grows, reproduces, moves, feels, perceives, thinks, remembers, and wills. Descartes, who helped invent the idea that there is nothing more to matter than what can be expressed in the mathematical language of physics, re-conceived of the human body along exactly such abstract lines, as just one more bit of quantitatively definable unconscious physical clockwork among others. The more grossly physical human activities—walking, digesting, and the like—were reinterpreted, accordingly, as mere movements of this insensate clockwork, differing in degree but not kind from the motions of a machine. Thinking, willing, perceiving, and the like, which had been abstracted out of the clockwork, were then reinterpreted as the activities of an immaterial res cogitans or "thinking substance" which somehow interacts with otherwise unconscious matter. Man, who had been an organic unity, a psychophysical whole, was redefined as a composite of two radically different abstractions: "body" (conceived of in purely mathematical terms) and "mind" (conceived of as pure thought).
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Materialists have essentially lopped off the latter abstraction while keeping the former. Their project has been to explain how thinking, willing, and perceiving can be assimilated to the material world as described by physics. Since that world has, ever since Descartes, been defined in a way that essentially excludes such features, it is no surprise that materialist theories have always seemed implicitly to deny the existence of consciousness, choice, and the like. And no surprise that some materialists have decided to bite the bullet and make this denial explicit. To be sure, Gazzaniga himself is keen to resist the tendency of some neuroscientists to deny the reality of moral responsibility. He emphasizes that there are physical systems with properties that are irreducible to those of their parts, and whose behavior cannot be predicted from what we know about the parts. He is thus critical of claims often made to the effect that neuroscientist Benjamin Libet's experiments have cast doubt on free will, on the grounds that descriptions at the level of neurons and at the level of consciousness are "complementary" and that Libet unduly privileges the former.
Yet Gazzaniga has by no means freed himself of the Reification Fallacy that underlies the reductionism he deplores. Although he allows that it is at least problematic how consciousness and choice can be attributed to human beings as a whole, he casually attributes other mental properties to the parts of human beings. Hence we are assured that the left hemisphere of the brain "interprets" incoming data, that the right hemisphere "saw" items shown to it, that the speech center "replied" to a question, and so forth. This is like saying that it is an open question whether a puddle of water as a whole is really liquid but that we know for sure that individual water molecules are liquid. In fact, of course, only water as a whole can intelligibly be said to be liquid, whereas the concept of liquidity doesn't even apply to the individual molecule. And in fact only human beings as a whole can intelligibly be said, for example, to interpret, to see, and to reply to questions, while these concepts do not even apply at the level of neural structures.
In general, and like many other neuroscientists, Gazzaniga speaks of the brain and its parts as if they were somehow more real or fundamental than the whole human organism from which they have been abstracted. Hence Gazzaniga simply assumes that the higher-level phenomena of consciousness and choice have, if they are to be explained, somehow to "emerge" from various lower-level neural structures and processes—as if the latter "wore the trousers," metaphysically speaking; and as if they could even be made sense of in the first place apart from the higher-level behavioral and mental phenomena with which they are associated and by reference to which we interpret them.
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The end result is that Gazzaniga's position, like other "emergentist" theories, comes across as obscurantist. That is inevitable given that it rests on the same tendency to confuse abstractions with concrete realities that underlies the thinking of his more ruthlessly consistent materialist rivals. Given that starting point, reductionism and eliminativism are bound to seem the only serious options and "emergentism" a dodge. A more promising approach to the problem of free will can only proceed, not from the abstractions we've inherited from Descartes and his materialist successors, but precisely by seeing through those abstractions—by emphasizing (as Aristotle and Ludwig Wittgenstein did) that consciousness, choice, and other mental phenomena can properly be understood only when predicated of the concrete human being as an irreducible whole. The neuroscientist M.R. Bennett and the philosopher P.M.S. Hacker have, in their book Philosophical Foundations of Neuroscience (2003), ruthlessly exposed the confusions and fallacies to which Gazzaniga and too many other neuroscientists are prone. If Gazzaniga is aware of their criticisms, he does not reply to them here.
Until we see through scientism we will not have freed ourselves from the illusion that free will is an illusion.