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By incorporating neuroscience into philosophy, Patricia Churchland has undermined several staples of Philosophy 101.
The thinking of Descartes, for example, who believed the soul was responsible for all mental functions, has been rendered quaint by research showing that the self-whatever it is-clearly emerges from the physical brain. Churchland's most recent book, Touching a Nerve, is subtitled The Self as Brain, and visits some of the evidence that all of our emotions, thoughts, memories, and behavior spring from neural activity and nothing but-no soul required.
Immanuel Kant, another seminal figure in the history of philosophy, famously asserted the existence of a universal "categorical imperative"-a rule regarding moral behavior that allows no exceptions. Churchland subverted that notion with her previous book, Braintrust: What Neuroscience Tells Us About Morality, which argues that our ethical impulses spring from our mammalian heritage rather than our evolved capacity for abstract thought. "The truth seems to be that the values rooted in the circuitry for caring-for well-being of self, offspring, mates, kin, and others-shape social reasoning about many issues," she writes. And it is that circuitry for caring, rather than God or reason, that drives us to resolve conflicts, seek justice, and defend our children, our kin, and our tribe.
Churchland's application of neuroscience to philosophical speculation, a practice now widely known as "neurophilosophy" (the title of her 1986 book on the subject) also undercuts the notion of free will espoused so vigorously by Jean-Paul Sartre and other existentialists. They urged people to accept responsibility for their choices, but with vast amounts of brain activity occurring below the threshold of consciousness, such assertions about free will seem naïve, says Churchland. She stops short, however, of asserting that humans have no free will at all.
"Sartre had this strange idea about free will," Churchland said from her home in San Diego, where she lives with her husband Paul Churchland, also a neurophilosopher. "If all he meant was you should take control of your life, that's fine. We hear Dr. Phil say that all the time. But given what we know about genetics, and the nature of brain/environment interactions, well ... you can't make yourself be whatever you want."
In effect, Churchland believes that humans, along with many other mammals, possess identifiable brain circuits that enable a certain amount of self-control, which makes choice possible. However, self-control varies widely from person to person.
"Any teacher will tell you that," Churchland said. "Some people need to struggle to achieve self-control and self-discipline. Even rats differ. Some can defer gratification and some are not so good at it."
Churchland's interest in neuroscience began while she was in graduate school, and encountered Word and Object, a book by Willard Van Orman Quine, who held that science rather than the thoughts of earlier philosophers should define reality. "Science is not a substitute for common sense but an extension of it," Quine said in his 1954 essay, "The Scope and Language of Science."
At the time many other young philosophers were focused on "conceptual analysis," which holds that breaking concepts into their constituent parts and analyzing how the parts interact will yield knowledge. "I thought, concepts are just the words we happen to use today to reflect our current state of knowledge," Churchland said. "They don't reflect ultimate knowledge, or the knowledge we'll have in 200 years. Quine said if you believe that simply reflecting on the concepts you use will lead to finding deep truths about the nature of things, you're misguided, and that had profound effect on me."
When she and her husband moved to Winnipeg, Churchland decided to study the anatomy of the brain. "I went to the medical school and talked to the head of the anatomy department, and he thought it was a wonderful idea to have a philosopher learn about the brain," she said. "He introduced me to neurologists and said, why don't you come along on neurology rounds? Winnipeg is vast but sparsely populated, so anyone who has anything neurologically wrong comes to Winnipeg. I saw fascinating cases, and it started to feed my philosophy right away."
This was the dawn of neuroimaging and other techniques that revealed the form and function of the living brain in striking detail. At the same time experiments were calling into question conventional notions about the mind. Canadian neurosurgeon Wilder Penfield, for example, had developed a technique of mapping the brain of epilepsy patients to identify regions he should avoid when performing surgery to control their seizures. With the patient awake (the brain itself has no pain receptors) he would apply a small electric current to the cortex and ask the patient to describe the sensation. "One lady said, I smell burnt toast," Churchland recalled. "What room is left in the argument for a soul if you can stimulate the brain electrically and the patient smells burnt toast?"
Roger Sperry conducted experiments with epilepsy patients who had undergone surgery to sever the corpus callosum, the bundle of nerves linking the left and right hemispheres of the brain, to prevent their seizures from spreading from one side to the other. Such patients appeared to be normal after the surgery, but Sperry found that when a word or image was presented to their left eye only, the patients could not identify what they saw because the information that eye sent to the right hemisphere could not cross over to a language area located in the left.
"That put the final nail in coffin for Descartes' conception of the soul," Churchland said. "If one hemisphere can know something the other doesn't know, how can there be a unified non-physical soul that does the thinking and knowing and believing? How can that possibly be true? That is a huge effect philosophically."
Today, the role of the brain in human experience seems beyond dispute, but some philosophers still cling to the traditional tools of introspection and disciplined thought. At a recent philosophical conference Churchland attended, a philosopher stood up, gripped the back of the chair in front of him, and hollered, "I hate the brain! I hate the brain! I hate the brain!"
At the time Churchland was puzzled. "Whatever could he mean?" she asked after recounting the incident in Touching a Nerve. Now she believes knowledge about the brain disrupts those lingering beliefs about the existence of a soul.
But Churchland finds the absence of the soul to be liberating because it shifts attention to the here and now. "If you think you have to defer all satisfaction and enjoyment, and sacrifice for a hereafter that maybe isn't even there-that I find deeply dissatisfying," she said.
Knowledge about the brain may have reduced many traditional philosophical assertions to historical curiosities, but Churchland believes that opens the way to fresh inquiry.
"I think neuroscience has rendered the staples of Philosophy 101 obsolete in the same way that the periodic table of elements rendered alchemists obsolete," she said. "Alchemists were often brilliant in the ways they tried to understand the nature of chemical reactions, but they got involved in spiritual discussions about the essence of this becoming the essence of that. Once chemistry became a real science, the alchemists were done."
In the same way, philosophers have sometimes become mired in metaphysical speculation, but neuroscience, Churchland hopes, will lead them to questions that are much more interesting and important. As she summarized the situation in her book, Neurophilosophy, "the heyday of unfettered and heavy-handed philosophical speculation on the mind has gone the way of the divine right of kings."