How do neurons turn into minds? How does physical “stuff”atoms, molecules, chemicals, and cellscreate the vivid and various worlds inside our heads? The problem of consciousness has gnawed at us for millennia. In the last century there have been massive breakthroughs that have rewritten the science of the brain, and yet the puzzles faced by the ancient Greeks are still present. In The Consciousness Instinct, the neuroscience pioneer Michael S. Gazzaniga puts the latest research in conversation with the history of human thinking about the mind, giving a big-picture view of what science has revealed about consciousness.
The idea of the brain as a machine, first proposed centuries ago, has led to assumptions about the relationship between mind and brain that dog scientists and philosophers to this day. Gazzaniga asserts that this model has it backwardbrains make machines, but they cannot be reduced to one. New research suggests the brain is actually a confederation of independent modules working together. Understanding how consciousness could emanate from such an organization will help define the future of brain science and artificial intelligence, and close the gap between brain and mind.
Captivating and accessible, with insights drawn from a lifetime at the forefront of the field, The Consciousness Instinct sets the course for the neuroscience of tomorrow.
|Publisher:||Farrar, Straus and Giroux|
|Product dimensions:||5.90(w) x 9.10(h) x 1.20(d)|
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HISTORY'S RIGID, ROCKY, AND GOOFY WAY OF THINKING ABOUT CONSCIOUSNESS
"Speak English!" said the Eaglet. "I don't know the meaning of half those long words, and, what's more, I don't believe you do either!"
— Lewis Carroll, Alice's Adventures in Wonderland
SIGMUND FREUD DIED the year I was born — 1939. That year there were a lot of zany ideas being kicked around about the nature of our psychological lives, many of them dreamed up by Freud himself. He is not popularly remembered as such, but Freud was a biologist at heart, a reductionist. He was committed to the belief that the brain generated the mind in a deterministic way, a view shared by many of today's neuroscientists. Now we recognize that many of his ideas were pure fantasy, but up until the 1950s they were so broadly accepted that they were the dominant testimony for psychological issues in a U.S. court of law!
It has been in my lifetime, not Freud's, that humankind has learned the most about how the brain does its tricks. Wild speculation about the forces governing our mental lives has given way to specific knowledge about the molecular, cellular, and environmental influences that underlie our existence. Indeed, the past seventy-five years of research have provided a wealth of information about the brain, sometimes even yielding organizing principles. I am sure Freud would have reveled in our new world and would have gladly put his incredible imagination to work on the new science of the brain. Yet the deep puzzles that faced scientists of all stripes in the previous century, and indeed going back to the ancient Greeks, are still present today. How on earth does lifeless matter become the building blocks for living things? How do neurons turn into minds? What should be the vocabulary used to describe the interactions between the brain and its mind? When humankind finds some answers, will we be disheartened by what they are? Will our future understanding of "consciousness" simply not be fulfilling? Will it be simple yet cold and harsh?
Wading into the history of the study of consciousness is daunting. For one thing, it is littered with the complex and abstract writings of philosophers. Even John Searle, one of today's leading philosophers of consciousness, has admitted: "I probably should read more philosophy than I do. But I think a lot of works of philosophy are like root-canal work, you just think you've got to get through that damn thing." Add to that the view of the great philosopher David Hume, who provided strong arguments that most of the questions asked by philosophers simply couldn't be answered using the methodologies of logic, mathematics, and pure reason. Nonetheless, philosophers got us thinking about the mind, the soul, and consciousness. From ancient times on, they have had a huge influence.
"Consciousness" is a relatively modern idea. The very word, as now broadly used in dozens of contexts (Marvin Minsky would call it a "suitcase word" because it is packed full of various meanings), was invented in its modern sense only in the mid-seventeenth century by René Descartes. It does have origins in the Greek word oida — "to have seen or perceived and hence to know" — and the Latin equivalent scio, "to know." But the ancients did not have an explicit concept of consciousness. There was interest in how the mind worked, where thoughts came from, and even whether a purely physical process was involved, but most early thought wound up concluding that mental life was the product of an immaterial spirit. And when consciousness is framed as immaterial spirit, it's hard to start thinking about underlying mechanisms!
Over the centuries, the concept of the mind and the concept of the soul have been involved in an on-again, off-again relationship. For most of written history, the very idea that personal psychological reality was a thing, a something to be studied, was largely nonexistent. Our brains, our thought structures, and our emotions presumably haven't changed, so what were we humans thinking about? But, as will become evident, the concept of consciousness has radically changed over the past twenty-five hundred years. Its ethereal beginnings and its current meaning have little to do with each other.
We humans need a new way to think about the problem, and with luck, this book may offer some new beginnings. First, however, as is always the case, it's best to look back before plunging forward.
Early Stirrings: Successes and Blunders
The ancient Egyptians and Mesopotamians were the Western world's philosophical forebears. In their concept of the world, nature was not an opponent in life's struggles. Rather, man and nature were in the same boat, companions in the same story. Man thought of the natural world in the same terms as he thought of himself and other men. The natural world had thoughts, desires, and emotions, just like humans. Thus, the realms of man and nature were indistinguishable and did not have to be understood in cognitively different ways. Natural phenomena were imagined in the same terms as human experience: generous or not so much, dependable or spiteful, and so on. These ancients of the Near East did recognize the relation of cause and effect, but when speculating about it they came from a "who" rather than a "what" perspective. When the Nile rose, it was because the river wanted to, not because it had rained. There was no science to suggest otherwise.
Not so with the ancient Greeks. The earliest Greek philosophers were not priests charged by their communities to consider spiritual matters, as they were in the Near East. They were not professional seers. They were a bunch of amateurs puttering around in their garages unconstrained by dogma, curious about the natural world, and happy to share their thoughts. When they started to ask about their origins, they did not ask "who" the progenitor was, they asked "what" the first cause was. This was a monumental change of viewpoint for humankind that the archaeologist and Egyptologist Henri Frankfort called "breathtaking":
[T]hese men proceeded, with preposterous boldness, on an entirely unproved assumption. They held that the universe is an intelligible whole. In other words, they presumed that a single order underlies the chaos of our perceptions and, furthermore, that we are able to comprehend that order.
Frankfort goes on to explain how the Greek philosophers were able to make this leap: "The fundamental difference between the attitudes of modern and ancient man as regards the surrounding world is this: for modern, scientific man the phenomenal world is primarily an 'It'; for ancient — and also for primitive — man it is a 'Thou.'"
A "Thou" is a someone with beliefs, thoughts, and desires, doing their thing, not necessarily stable or predictable. On the other hand, "It" is an object, not a friend. "It" can be related to other objects in whatever seems the most reasonable organization. One can build and expand on these relationships and seek universal laws that govern behavior and events under predictable, prescribed conditions. Seeking the identity of an object is an active process. On the contrary, understanding a "Thou" is a passive process in which one first receives an emotionally charged impression. A "Thou" is unique and unpredictable and known only insofar as it reveals itself. Each "Thou" experience is individual. You can coax a story or a myth from an interaction with a "Thou," but you cannot draw a hypothesis. The transition away from "Thou" and toward "It" made scientific thinking possible.
The Greeks' huge advance in perspective created an atmosphere that catapulted Aristotle into a scientific life. Aristotle's stance was that the job of science was to account objectively for the "why" of things, which led to his doctrine of causality. For him, scientific knowledge about something (say, some X) included all the ways the "why" question could be answered: if X was caused by Y, or if Y was at least a necessary condition in order for X to happen, then this is the type of assertion that belongs to science. He postulated four causal categories: material, formal, efficient, and final. So if one were to ask "Aristotle, why a cart?," he would tell you the material cause was wood, the formal cause was its blueprint, the efficient cause was its construction, and its final cause was ... he just wanted one.
For Aristotle, the natural world was a web of what biological theorist Robert Rosen calls causal entailments: X comes with all its Ys. Rosen points out that Aristotle's whole idea was to show that no one mode of explanation sufficed to understand anything, because the causal categories do not entail each other. For example, knowing how to build something does not entail understanding how it works; knowing how something works does not entail knowing how to build it. Also, for Aristotle, science was content-determined. It was independent of the method by which it was studied.
The scientific method as practiced today is a formal system in which a hypothesis produces its inferences, that is, its effects: the hypothesis entails its effects. Another way to say this is that the cause comes before the effect. This presents a problem when asking Aristotle's final-causation "why" question. Let's go back to "Why the cart, Aristotle?" Why did Aristotle have a cart parked in front of his home when hours earlier it had been parked at Acropolis Depot? He had seen the cart (which entailed the effects of the material, formal, and efficient causes) and wanted it. Here, the tables were turned and the effect came before the cause. This is a no-no in the Newtonian world, where a state can only entail subsequent states. Thus, Aristotle's final causation, as a separate category, was lost to science. We will see later what harm this has done to biology.
Among other things, Aristotle wanted to know more about the human body and how it worked. This was a bit challenging, since the Greeks had a taboo against human dissection. Aristotle skirted this issue by performing numerous animal dissections. From what he learned, he devised a system of classifying organisms, the scala naturae, a graded hierarchical scale based on the type of "soul" each possessed. At the base were plants, which he posited have a vegetative soul responsible for growth and reproduction. Needless to say, man sits at the top of the scala naturae.
Aristotle didn't stop there. He proposed that animals possess a sensitive soul powering self-movement, perception, sensation, appetite, and emotion. Unique to humans and nested within the sensitive soul is a rational soul that provides us with the special powers of reason, rational will, thought, and reflection and sets us apart from those lower on the scala. Most important, and reflecting the revolution in human thinking, the "knowledge" of these powers arrived at not by sheer introspection or mental meanderings, but by observing how one connects with the surrounding world. The "it," that is, an object such as the world around us, could be studied and examined. We forget that this very idea, now commonly accepted, didn't exist a few thousand years ago! Clearly, ideas do have consequences, and, happily, we continue to be captivated by the idea and power of scientific observation.
Aristotle got the process of science right, but his conclusions about where thoughts come from were all off. If a modern student had made a mistake like the one he made, the student would have failed the course. Aristotle knew from the actions of animals and humans that they can perceive the world. From his dissections, Aristotle noted that some animals had no visible brains at all. He concluded, therefore, that the brain appears to be of not much account. The first thing he saw appearing in the embryos he studied was the heart, so he put the soul there, which in the case of humans included the rational soul. Aristotle did not mean "soul" in a spiritual sense, as he did not think it continued on after death. He meant the organ that gives rise to sensation, to our knowledge of the world. He thought that the rational soul, which was the source of human intellect, required some perceptual mechanisms; therefore, it required a body with its parts and organs. Yet he did not think that there was a body part or an organ that thinks. Aristotle never even mumbled the word "conscious," but he did ask, "How do we know our own perceptions?" Overall, Aristotle got the ball rolling and got people thinking about humankind's physical nature.
The monumental stirrings that started in Greece were quickly exported. In 322 B.C., not long after Aristotle died, Herophilus and Erasistratus, two Greek physicians living in Alexandria, defied the taboo on dissecting human bodies and went at it. They became the first to discover the nervous system and write about it. They also found the ventricles, the empty chambers inside the brain. Herophilus decided that these chambers must be where the intellect was located, and that from them, spirits flowed down through hollow nerves out to the muscles, making them move. While they didn't get it exactly right, they are commonly credited with being the first neuroscientists. Unbelievable as it now may seem, the Greek culture that engineered and built the Parthenon didn't know about brains. And the Egyptian culture that engineered and built the pyramids didn't know how the brain worked at all.
History rattled along for another four hundred years, a microsecond in evolutionary time. Rome became the dominant force in the Mediterranean and somehow was able to attract the wondrous physician Claudius Galenus (Galen) from Pergamum, a Greek city on the Aegean coast of modern-day Turkey. Galen finished his medical training an empiricist, having immersed himself in the teachings of Herophilus and Erasistratus in Alexandria, now under Roman rule. In ancient Greece, the Empiric school of medical practice relied on the observation of phenomena and on experience, not on dogmatic dicta. Galen returned to Pergamum for his first job: gladiator doctor. Because the Romans, like the Greeks, did not allow human dissection, Galen never did any. Instead, he honed his knowledge of anatomy and surgery with the gory remains of his patients and with daily animal dissections, primarily on Barbary macaques. He took his firsthand knowledge; a healthy helping of the teachings of his distant mentors, Herophilus and Erasistratus; and a pinch of Hippocrates' theory that the body was composed of four humors, and combined them into a new conception of the body and its machinations. He earned himself a stellar reputation. Soon he was on his way to Rome, and his growing fame led him to become the personal physician to the emperor, Marcus Aurelius.
Galen's contributions to medicine are stunning. He was the first to recognize that there is a difference between arterial and venous blood. We now know that arterial blood is rich with oxygen, while venous blood carries much less (your tissues have stolen it so they can breathe), a difference that is exploited in the functional magnetic resonance imaging (fMRI) studies of the brain that are the cornerstone of modern neuroscience. Galen gave the first depiction of the four-chambered human heart; he updated the knowledge of the circulatory system, the respiratory system, and the nervous system. He made some anatomical blunders, of course — one being a meshwork of blood vessels, the rete mirabile, which he located at the base of the human skull, based on dissections of oxen. This was a major mistake and a cautionary tale about inductive reasoning. As was shown years later, humans flat-out don't have a rete mirabile!
Nonetheless, Galen understood that food and breath are necessary for human life, and maintained that the body transforms them into the flesh and spirit. Amalgamating the works of Hippocrates, Plato, Socrates, and Aristotle, Galen came up with the idea of a material tripartite soul. Using Plato's designations of the rational, spiritual, and appetitive souls, he assigned each one an anatomical location: the rational soul was in the brain, the spiritual soul was in the heart, and the appetitive soul was in the liver. Each performed a separate function. The appetitive soul controlled the natural urges of the body, such as hunger and thirst, survival instincts, and bodily pleasures. It was animated by natural spirits. The spiritual soul contained the emotions and passions and was animated by a vital spirit that somehow formed in the heart from blood and air delivered via the lungs. The rational soul controlled cognition such as perceptions, memory, decision making, thought, and voluntary action. Galen saw no distinction between the mental and the physical. One can begin to see the groundwork being laid for such modern ideas as conscious versus subconscious, the id and the ego, the rational and the intuitive. The specifics are different, but the underlying ideas were emerging even in A.D. 200.
Excerpted from "The Consciousness Instinct"
Copyright © 2018 Michael S. Gazzaniga.
Excerpted by permission of Farrar, Straus and Giroux.
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Table of Contents
Part I Getting Ready for Modern Thought
1 History's Rigid, Rocky, and Goofy Way of Thinking About Consciousness 11
2 The Dawn of Empirical Thinking in Philosophy 29
3 Twentieth-Century Strides and Openings to Modern Thought 55
Part II The Physical System
4 Making Brains One Module at a Time 83
5 The Beginnings of Understanding Brain Architecture 107
6 Gramps Is Demented but Conscious 133
Part III Consciousness Comes
7 The Concept of Complementarity: The Gift from Physics 155
8 Non-Living to Living and Neurons to Mind 175
9 Bubbling Brooks and Personal Consciousness 201
10 Consciousness Is an Instinct 225