What is a "soul"?

	Ghost in the Machine (the soul hypothesis debunked)
Body:	A Ghost in the Machine The existence of the soul http://www.ebonmusings.org/atheism/ghost.html Part 1: Introduction / Where is the Soul Hiding? Part 2: The Argument from Mind-Brain Unity Part 3: The God Part of the Brain Part 4: Philosophical Problems with the Soul Part 5: The Mysteries of Consciousness and the God of the Gaps Part 1: Introduction / Where is the Soul Hiding? Central to many religions, both Eastern and Western, is the doctrine of dualism: that there is a non-material essence called the soul that inhabits and animates our bodies and is the cause and the source of consciousness, personality, free will, thoughts, ideas, feelings, emotions, memories, the sense of self - in short, everything a person thinks of as "I". Theists typically believe that the soul survives the physical death of the body and goes on to whatever comes after death, be it an afterlife in Heaven or Hell or reincarnation in a new body. I am an atheist because I have found no evidence that leads me to believe that the supernatural claims of any religion are true, and the notion of the soul is no exception. In fact, as this essay will demonstrate, there is strong evidence against the existence of a soul in humans, pointing instead to the alternative of materialism - that the mind is not separate from the brain, but that it arises from and is produced by neural activity within the brain. Simply stated, the mind is what the brain does. As a practical matter, it should be easy to judge between dualism and materialism, because unlike most religious doctrines, the notion of the soul is an idea that would seem to have testable consequences. Specifically, if the human mind is the product of a "ghost in the machine" and not the result of electrochemical interactions among neurons, then the mind should not be dependent on the configuration of the brain that houses it. In short, there should be aspects of the mind that owe nothing to the physical functioning of the brain. Until recently, this prediction was difficult to test, but modern scientific innovations have thrown light on the subject. Medical techniques such as CAT scans (short for computed axial tomography), PET (positron emission topography), and MRI (magnetic resonance imaging) allow the structure and function of the living brain to be studied. Scientists can see which areas of the brain "light up" with activity when a healthy person performs a mental task, or they can examine patients who have suffered injury or disease to see which parts of the brain, when damaged, correspond to which deficits of neural function. And already, a disappointing result for theists has emerged. Some mental functions are localized, while others are more diffuse, but there is no aspect of the mind that does not correspond to any area of the brain. In fact, we know precisely which brain regions control many fundamental aspects of human consciousness. The image of the brain that is familiar to most people - the organ of convoluted gray matter, about the size of two fists held together - is actually an image of just the cerebrum, the outermost and topmost area of the brain. In humans, the cerebrum takes up about 80% of total brain volume, and is responsible for most higher-order cognitive functions. The thin outer layer of the cerebrum, only a few millimeters thick, is called the cerebral cortex or simply cortex for short, and it is this which has the distinctive wrinkled, folded and convoluted gray appearance ("cortex" is Latin for "bark"). The cerebrum is divided into two hemispheres, the left and the right, which are basically symmetrical in structure, mirror images of each other. There is some specialization of function between the two; for example, in most people language is controlled entirely by the left hemisphere. However, to a large extent the two hemispheres do similar jobs. For example, each one receives sensory input from, and sends motor commands to, one side of the body. Each hemisphere is divided into four main regions, called lobes: the frontal lobe, the temporal lobe, the occipital lobe, and the parietal lobe. Roughly speaking, the occipital lobes are located in the rear of the brain, the temporal lobes on the bottom, the parietal lobes on top of the brain, and the frontal lobes, as their name implies, toward the front, behind the forehead (Austin 1998, p. 150). Each lobe performs a variety of functions. The temporal lobes, for example, play an important role in emotional response, memory, and hearing (and therefore language). A set of structures in the brain collectively called the limbic system, which is responsible for the former two functions, lies chiefly within the temporal lobes. The occipital lobes are concerned primarily with vision, though the parietal lobes also play a part in this; the parietal lobes also process information from other senses, especially touch. Finally, the frontal lobes seem to be responsible for many of the qualities we think of as distinctively human, including personality and what is called "executive" behavior: judgment, motivation, planning and goals, regulating and inhibiting actions, making decisions, controlling attention, and responding appropriately to external events and stimuli, among other things. The functions of the frontal lobes, and the changes that can be produced by damaging them, will be discussed in much more detail later in this essay. With this basic framework in mind, we can examine more specific aspects of brain function. For example, a section of the brain called Broca's area, usually within the left frontal lobe (in left-handed people it may sometimes be on the right side instead), controls the ability to produce speech. When this area is damaged by a stroke or other injury, the result is a condition called Broca's aphasia, which renders the victim mute, able to understand speech but unable to speak himself. A nearby section called Wernicke's area, in the left temporal lobe, performs the opposite role: it gives us the ability to understand speech by storing the memories of how words sound. Damage to this area produces Wernicke's aphasia, in which the sufferer cannot understand speech, either his own or others', and speaks only in meaningless babble. (Since the victim has lost all memory of what words are supposed to sound like, he is usually unaware that there is anything wrong with him, and does not understand why he cannot be comprehended by others.) While this jargon often sounds very much like a language and indeed is often mistaken for a foreign language by someone unfamiliar with the condition, it conveys no meaning (Heilman 2002, p. 4). There are evident implications for the sects that believe in glossolalia ("speaking in tongues"). Other sections of the brain's left hemisphere are essential to other aspects of communication. The structure known as the left angular gyrus contains the memories of how words are spelled, while the supramarginal gyrus converts speech sounds into letters (Heilman 2002, p. 49). Damage to these systems, both of which are within the parietal lobe, can result in inability to read or write, respectively known as alexia and agraphia. (Bizarrely, some people with specific types of damage to these regions can write but not read.) The left angular gyrus also seems to play a role in mathematical ability, since people who suffer damage to it sometimes become unable to do even the simplest calculations (Ramachandran 1998, p. 19). Damage to the entire language area of the left hemisphere produces a condition called global aphasia, in which the sufferer is completely unable to communicate; this syndrome will be discussed in more detail later on. The ability to synthesize sensory input into a coherent picture of the world is associated with physical regions of the brain. Most critical of all our senses is vision, and the brain devotes more resources to visual perception than to any other sense. The occipital lobes receive input from the eyes; cell groups within them are specialized to process specific aspects of vision such as color, edge, shape and motion (Heilman 2002, p. 183, 184). Information from the visual system then splits into two streams: the superior parietal lobe's "where" system, which helps us form spatial coordinates of objects and navigate in our environment, and the inferior occipital and ventral temporal lobes' "what" system, which tells us what it is we are looking at (p. 100). Other regions, such as the right parietal lobe, control sensory perceptions of our own body; damage to this region produces a truly bizarre disorder called asomatognosia, in which the sufferer is unable to recognize his own body as belonging to him (p. 119). Electrical stimulation of the right angular gyrus, a substructure of the right parietal lobe, can cause out-of-body experiences (Blanke et al. 2002). Still other brain regions control aspects of consciousness more fundamental than the ability to communicate or navigate. While the left hemisphere is typically responsible for understanding language per se, the right hemisphere mediates emotional aspects of communication, such as the tone of someone's voice or the expression on their face. Damage to the parietal and temporal lobes of the right hemisphere can leave a person unable to comprehend emotional displays in others (Heilman 2002, p. 56). Our emotions also arise from the functions of the brain. The left hemisphere seems to govern the expression of positive emotions such as happiness and joy, while the right hemisphere primarily governs negative ones such as anger and sadness. Those who suffer damage to their left hemisphere (leaving the more volatile right hemisphere "in charge") often become severely depressed, but right hemisphere damage can leave a person emotionally indifferent, even constantly euphoric (p. 75-76). Electrical stimulation of one part of the brain, a part of the limbic system called the amygdala, can produce intense fear (Heilman 2002, p. 74), while stimulation of other regions can cause uncontrollable laughter and feelings of mirth (Ramachandran 1998, p. 201), and stimulation of yet a third region, the insula, can produce feelings of nausea and disgust (Glausiusz 2002, p. 33). Electrical stimulation of a fourth region, the septum, produces consistent sensations of pleasure, and frequently causes a sudden shift in mood from depression to optimism (Austin 1998, p. 170). Memory, a fundamental aspect of consciousness, is strongly tied to brain function as well. A small brain region called the hippocampus, among other structures in the limbic system, is critical for forming new factual memories (Heilman 2002, p. 150); the effects its destruction has on a person are nothing short of profound. The question now arises, where in all of this is the soul? Which brain lobe does it inhabit? Where is it hiding in this tangle of neurons and synapses? In the seventeenth century, the philosopher Rene Descartes proposed that the soul interacted with the brain through the pineal gland, based on his observations that it is located near the center of the brain and is the only brain structure that is single, not paired. Unfortunately for Descartes, today we know the pineal gland is merely part of the endocrine system; its main function is to produce melatonin, a hormone that regulates sleep-wake cycles and influences the immune system, among other things (Heilman 2002, p. 3). So where is the soul hiding? Area after area of the brain has yielded up its secrets to the probing of neuroscience, and not a trace of it has been found. The more our knowledge advances, the less reason we have to suppose that it exists, and the less sustainable the dualist position becomes. All the evidence we currently possess suggests that there is nothing inside our skulls that does not obey the ordinary laws of physics. This is not to imply that there is nothing wondrous or amazing about the brain. On the contrary, it has been called, with some justification, the most complexly organized form of matter in the universe. The average human brain has over one hundred billion neurons, connected by hundreds of trillions of synapses. So immense is the complexity of this system, it has been calculated that the number of theoretically possible brain states exceeds the number of elementary particles in the known universe (Ramachandran 1998, p. 8). The brain's raw computational power has been estimated to be between 10 trillion and 10 quadrillion operations per second (Merkle 1989). (By way of comparison, one of the fastest supercomputers in the world, the Earth Simulator in Yokohama, Japan, can perform 36 trillion calculations per second.) That our minds arise from the workings of our brains is nothing to be dismayed about. On the contrary, the fires of evolution have spent over four billion years forging the brain into an engine of staggering complexity and computational power only to bequeath it to us. We have been given a unique and priceless privilege, a gift unlike anything else in the known universe. To understand this heritage can only uplift us, and those who would assert that this organic marvel can accomplish nothing on its own without the help of fading shadows of superstition, are only cheating themselves by replacing a greater wonder with a far lesser one. But in the end, it is the evidence that must decide the question, and so it is to the evidence I shall turn. Part Two of this essay will set forth and defend the position that, not only is there no evidence for the existence of the soul, but that there is strong positive evidence against the existence of the soul, deploying an argument I have styled the argument from mind-brain unity. Part Three will discuss the neurological causes of religion, arguing that all religious experience can be fully and parsimoniously explained as the result of electrochemical activity within the brain. Part Four will lay out some additional arguments against the existence of the soul, and finally, Part Five will consider the greatest and most enduring mysteries of neuroscience - the source of sensory perceptions, of free will, of consciousness - and will show that these questions in no way offer any support to theism. Part 2: The Argument from Mind-Brain Unity What does the soul do? Remarkably, I have yet to find any theist source which explains this. Those which address the topic of the soul seem content to assume that everyone knows what it is and what functions it is responsible for. However, although no theist source I have come across clearly explains the nature and function of the soul, it is fairly simple to deduce these properties based on what theists claim happens to one's soul after death. In the belief structure of many religions, when a person's body dies, their soul departs and goes to face God, where it is judged based on that person's actions in life. If the person has been virtuous, the soul is admitted to Heaven for an eternity of reward; if the person has been wicked or sinful, their soul descends to Hell for an eternity of punishment. It is further asserted by these religions that throughout this process there is a continuity of consciousness; i.e., the soul will be self-aware, will feel that it is the same person it was when it was embodied, and will in a sense be the same person, so that the reward or punishment will be justified. Given this, it is relatively easy to work out what the soul must do. If my soul is the part of me that thinks of itself as "I", that makes me the person I am, and that bears responsibility for my actions during life, then it must be responsible for three things: identity, personality, and behavior. Identity is consciousness, self-awareness, my recognizance of myself as a distinct and autonomous being that is continuous through time. Personality is comprised by the character traits that in combination make me a unique agent. Behavior is the sum total of the acts I perform, whether for good or for bad, during my life. To an extent, these three categories blend into each other; identity encompasses personality, and personality determines behavior - but if dualist theology is correct, it must ultimately be the soul, and not the brain, that is the source of all three of them. However, as an atheist, I argue that dualist theology is not correct - that these three things are not separate from the brain, are not even linked to the brain, but are unified with the brain. The evidence shows that they are completely determined by the physical configuration of the brain, and that a change to this configuration can alter or eliminate any of them. In short, I will show that, as the materialist position predicts, every part of the mind is entirely dependent on and controlled by the brain. This is what I call the argument from mind-brain unity, and I feel it is one of the strongest arguments against many varieties of theism. After all, if there is an immortal soul, why would it be subordinate to flawed biology? If there is a god who is fair and just, and who punishes or rewards us for our actions, he would not set things up so that these actions can be dictated or altered by brain chemistry, genes, or other factors over which we have no control. Unless he is an unjust tyrant, he would make our actions the result of the individual's free choice. This is consistent with the idea of consciousness arising from a spiritual soul not subject to the weaknesses of the physical body. Unfortunately, both of these ideas are contradicted by the evidence. The evidence is undeniable that our identity, our personality, and our behavior are unified with the brain, and can be dramatically influenced by causes beyond our control which affect the brain. Following are case studies that demonstrate this principle in all three areas. (Note: Except in the case of Phineas Gage, discussed below, the sources which provided these cases have fictionalized the names and circumstances of the sufferers, as is standard practice to protect their anonymity. In all cases, I have followed the lead of these original sources in using these details. The clinical aspects of these cases, however, are all true.) Unity of Identity Pure Amnesia Callosal Disconnection Alien Hand Syndrome Paralysis and Denial Capgras' Syndrome Unity of Personality The Strange Case of Phineas Gage Frontotemporal Dementia Euphoria and Emotional "Deadness" Psychosis and Depression Unity of Behavior Behavioral Alterations Caused by Tumors Akinesia Environmental Dependency Syndrome Aphasia and Inability to Pray Akinetic Mutism Unity of Identity Pure Amnesia Though there are far more unusual neurological disorders that support the argument from mind-brain unity, the first one this essay will examine is relatively well-known and straightforward: amnesia, the loss or disturbance of memory. The best-known type of amnesia is the inability to remember past events due to a blow on the head or some other brain trauma. This condition is known to neurologists as retrograde amnesia, and in most cases is transient, encompassing only the most recent memories and lasting only a brief period of time. However, the type this essay will deal with is less well-known and more severe in its repercussions: anterograde amnesia, the inability to form new memories. Permanent anterograde amnesia - a total inability to form new memories, without impairing intellectual capacity in any other way - is also known as pure amnesia. (This condition was dramatized in the 2000 film Memento.) It is often the result of alcohol abuse (a condition called Korsakoff's syndrome), but can have other causes as well. The most famous case on record is that of a man identified only by his initials, H.M., who lived in the mid-twentieth century. After a childhood head injury, H.M. began to suffer from severe epilepsy, with frequent seizures originating in the temporal lobes of his brain. The seizures did not respond to medication, and to cure him, surgeons resorted to removing the anterior portions of both his temporal lobes. This procedure did give him relief from the seizures, but it had an unintended side effect. The portions of his brain that were removed contained the two lobes known as the hippocampi (singular, hippocampus - named after the seahorses they resemble in shape) that are now known to be critical for the formation of new memories. As a result of the surgery, H.M. acquired a severe case of anterograde amnesia. Though his intelligence was unaffected and he retained most of the memories he had had before the surgery, he completely lost the ability to form new ones. As soon as he ceased to pay attention to something, he completely forgot that he had ever experienced it. He did not know what date it was, knew nothing of current events, and was unable to remember conversations a few minutes after they were over. Drs. Brenda Milner and Suzanne Corkin studied him for years, but he never recognized them or came to know them; they had to reintroduce themselves each time they met him (Heilman 2002, p. 149-150). (For a moving account of H.M.'s loss, see "The Day His World Stood Still".) Memory is such a natural and integral part of everyday functioning that it is difficult to imagine what an existence without it must be like. Likewise, it is almost impossible to overstate the terrible and tragic nature of this condition and the importance of what H.M. and people like him have lost. Another case study, however, may make the point clearer. In 1985, a professional musician named Clive Wearing fell ill with a severe case of encephalitis - a viral infection that attacked his brain, producing inflammation and substantial brain damage. With the aid of modern medicine, he survived and made a recovery, but it soon became apparent that he had not survived unscathed. Like H.M., his hippocampi had been destroyed, leaving him with a permanent case of total anterograde amnesia. Superficially, Wearing seems unchanged. His emotions are intact, as are his intellectual and rational faculties, and his musical abilities are unaffected. He still recognizes his wife and greets her with happiness and affection when he sees her, and he can still play the piano or harpsichord with all the skill he had before his illness. But something about him is deeply and fundamentally wrong. So dense is his amnesia that he can literally remember nothing from more than a few minutes before, and as a result, he continually believes that he has only just recovered consciousness. He fills his journal with pages and pages of the same entry, repeated endlessly: "Now I am completely awake, for the first time in years" (Time-Life 1991, p. 85). He does not recognize or remember making any earlier entries, denies being the author if asked, and rapidly becomes angry if it is pointed out that they are in his handwriting. Likewise, every time Wearing's wife Deborah visits him, he immediately forgets the visit as soon as she leaves the room. When she returns, even if she has been gone for only a few minutes, he greets her with joy and affection, declaring that he has not seen her for months and asking how long he was unconscious (Baddeley 1990, p. 5). Wearing's brain damage has left him completely incapable of learning any new facts. When attempts are made to teach him anything, he easily becomes frustrated and angry, and of course within minutes has utterly forgotten the experience. He could (and does) read the same book or watch the same TV show over and over, and every time is equally surprised and delighted at the outcome. His bout with illness destroyed some of his past memories as well: he remembers the events of his life only in sketchy outline, and he no longer knows who the Queen of England is, or who wrote the play Romeo and Juliet (ibid.) Wearing, of course, is completely helpless in everyday life and requires constant care. But there is another implication of his condition that is, depending on how one views it, either a small mercy or the cruelest irony of all. That implication is this: Clive Wearing is not aware, and cannot be made aware, that there is anything wrong with him. He cannot learn the nature of his condition any more than he can learn any other new information. If he were to be told what had happened to him, he would undoubtedly experience all the sensations of shock and dismay any average person would, and then would completely forget them moments later. Without memory, he is trapped in an endless, timeless present, with no past and no future. Barring some radical advance that would make it possible to repair his damaged brain, he will be this way until he dies. Though Clive Wearing's ability to form new memories is irreparably destroyed, he does remember, at least in broad outline, the events of his life. Not so for another patient with an even more severe amnesia, a patient studied by Antonio Damasio and colleagues. This patient, who suffered damage to both his hippocampus and his temporal lobes (thought to be important for storing memories), has total anterograde and near-total retrograde amnesia: he cannot form new memories or recall old ones. He is trapped in a permanent present, a void of consciousness without memory. "Indeed, he has no sense of time at all. He cannot tell us the date, and when asked to guess, his responses are wild - as disparate [as] 1942 and 2013.... This patient cannot state his age, either. He can guess, but the guess tends to be wrong. Two of the few specific things he knows for certain are that he was married and that he is the father of two children. But when did he get married? He cannot say. When were the children born? He does not know. He cannot place himself in the time line of his family life." (Damasio 2002, p. 69-71) As Dr. Damasio tells us, the patient's wife divorced him over 20 years ago, and his children are long since grown up and married. Does this man still have a soul? In what sense is he conscious? He is adrift in a world of darkness, a blank void with neither past nor future, merely an ever-moving present that continually fades from sight. One more case study will drive home the point of how devastating this condition is, how utterly it deprives a person of some fundamental aspect of their humanity. The hippocampus is not the only brain structure that seems to be vital for laying down new memories. It is part of a circuit in the brain involving several distinct regions, all of which seem to be equally important for that task. One such region, which connects directly to the hippocampus, is called the fornix, and Dr. Kenneth Heilman tells us of a patient named Flora Pape whose left and right fornices both had to be excised to save her from a life-threatening brain tumor. Mrs. Pape had lived in east Kentucky all of her life, until she and her husband both moved to Jacksonville, Florida, two years before her surgery. At the time of her surgery, she had two sons in their 20s, both of whom still lived in Kentucky. When she was discharged from the hospital, her husband drove her from Gainesville to their home in Jacksonville. After leaving Gainesville, her husband noticed that she was looking out the window and saying, "Oh, my!" He asked what was troubling her and she said, "What happened to the mountains?" He asked, "What mountains?" She replied, "You know, the mountains." He said, "There are no mountains here." She replied, "No mountains in Kentucky. We must be in the western part of the state. What are we doing here?" Mr. Pape had been told by [the doctor] that the surgery might make her memory worse, but he was still surprised. "Dear, we are not in Kentucky. We are in Florida." She asked, "Why are we in Florida?" He told her that they had moved to Jacksonville about 2 years earlier. She said, "Moved to Jacksonville? Why?" He told her that the company had asked him to transfer. She asked, "Where are we going now?" "Back to Jacksonville from Gainesville. You had some surgery on your brain. It was a tumor. The doctors think they got it all out. You are having some memory problems, but the surgeons hope it will improve with time." Then she asked, "Who is watching the boys?" "No one," he replied. "They are grown and live in Kentucky." "What do you mean, grown? They are still teenagers." "No, they are not. They are in their twenties. They are coming down this weekend to see you." She stopped asking questions for a few minutes and looked out of the car window. Then she turned to her husband and asked, "Where are all the mountains?" (Heilman 2002, p. 151-152) Like H.M., Clive Wearing and Dr. Damasio's patient, Mrs. Pape's memory disorder seems to be permanent, and no treatment known to medical science can cure it. The question must now be asked: According to dualist beliefs, what has happened to these people? Where are their souls? If any of them were not religious before the onset of their conditions (I was unable to find information on whether they were), they never will be now. Any proselytizer who tries to convert them has, at most, a few minutes to introduce himself, make the person's acquaintance, earn their trust, explain the tenets of the religion he is offering, and convince them to accept it. After that, they will forget and he will have to start all over. And if the religion requires any type of repeated behavior or ritual, that is out of the question - a few minutes after their conversion, they will have completely forgotten that it ever happened. Will God condemn them for this? Assuming these people were not religious, are they now doomed to Hell because their souls are trapped in an endless loop of brain chemistry? More to the point, how is this condition compatible with a thing such as the soul in the first place? As one researcher has put it, "the memories of a person define the self" (Persinger 1987, p. 53). Without memory, a person's identity is irrevocably altered. The effects of this condition are consistent with the materialist prediction that the mind is unified with the brain, but seem considerably more difficult to reconcile with dualism. Callosal Disconnection Our consciousness is normally continuous in two respects: it is continuous in space (there exists exactly one consciousness in each body) and in time (each body has exactly one consciousness per lifetime). This is as we would expect if the soul existed. After all, we could not fairly be judged for the actions of our body if we were only one of many presences inhabiting it and struggling to control it, nor could an elderly person be fairly held responsible for the sins of their youth, or vice versa, if the consciousness we possess throughout our lifetime is not the "same" consciousness at each point within our lifetime. However, the condition called pure amnesia proves that it is possible for brain damage to create a consciousness that is not continuous in time. What about a consciousness that is not continuous in space? Can a brain disorder produce multiple consciousnesses within a single body? For the purposes of this essay, multiple personality disorder (or dissociative identity disorder, as the American Psychiatric Association calls it) will not be considered. It is still a matter of considerable controversy whether this disorder actually even exists (see Piper 1998) and even if it does, it may be purely psychological in nature (Carroll 2002). For the argument from mind-brain unity, only definite conditions caused by physical neurological damage will be reviewed. As it happens, there is such a condition - one that is not quite as well-known as multiple personality disorder, but that is even more revealing about the way our brain, and therefore our consciousness, is organized. This syndrome is generally known as callosal disconnection. The human brain is divided into two hemispheres, the left and the right. These hemispheres are mirror images of each other, and perform many of the same functions. For example, each hemisphere receives sensory input from, and controls movements of, one side of the body. However, there is also some specialization. For example, in most people, language is controlled entirely by the left hemisphere. So that they can exchange information with each other, the two hemispheres are connected by a bundle of nerve fibers called the corpus callosum. However, in some people, the corpus callosum is damaged or severed. Sometimes this occurs accidentally, as the result of brain injuries such as stroke; sometimes it is done deliberately, as the result of a surgical procedure. The most common reason for such a procedure is to treat severe epilepsy: cutting the corpus callosum prevents seizures - storms of uncoordinated neural activity - that begin on one side of the brain from spreading to the other, and so affords sufferers some relief. However, doing so has a strange side effect that provides insight into the nature of consciousness. As previously stated, each hemisphere receives sensory input from one side of the body only. (Due to a quirk of evolution, our brains have their wires crossed - the left hemisphere controls the right side of the body, and vice versa.) However, also as previously stated, only the left hemisphere controls language. Therefore, when we perceive something on the left side of the body, that sensory information normally travels to the right hemisphere and then through the corpus callosum to the left, which can verbalize and describe what was perceived. But what happens if that connection is severed? Studies have repeatedly found that, if a patient with callosal disconnection is blindfolded and has an object put into their left hand, they will not be able to name or describe it (Heilman 2002, p. 128). The sensory information received by the right hemisphere cannot be transferred to the language systems of the left. However, since the right hemisphere controls movements of the left side of the body, including the left hand, the person will be able to use that hand to draw the object, or select it from among a group of similar objects, if asked to do so (Newberg and D'Aquili 2001, p. 23; Feinberg 2001, p. 92) - even while remaining unable to explain what they are doing or why. But there are even more important symptoms of callosal disconnection. One thing the right hemisphere controls is certain types of emotion. If an image with strong emotional associations is projected only to the left eye, so the visual signal can only travel to the right hemisphere, a person with callosal disconnection will experience the appropriate emotional response. But if asked to explain why they are feeling that emotion, the person will not stand mute. Instead, surprisingly, they will give a reason that is logical but completely unrelated to the true cause. As Andrew Newberg and Eugene D'Aquili write, "A split-brain patient shown a photograph of Hitler only in the right hemisphere, for example, might exhibit facial expressions indicating anger or disgust. But when asked to explain those emotions, the patient will often invent an answer, such as 'I was thinking about a time when someone made me angry.'" (Newberg and D'Aquili 2001, p. 23) Kenneth Heilman offers another, more concrete example, writing about the research of Dr. Michael Gazzaniga and his colleagues. In one experiment, they showed sexually suggestive pictures to a woman with callosal disconnection, flashing them only on the left half of a screen so only her right hemisphere could perceive them. The woman giggled and blushed, but when asked why she was doing so, she replied that she was thinking of something embarrassing (Heilman 2002, p. 129). Are these people lying? In one sense of the word, perhaps; but it seems clear that there is no conscious intent to deceive. Rather, researchers have concluded, what is happening is that the right hemisphere, upon seeing an image with strong emotional connotations, generates the appropriate response. However, due to the callosal disconnection, it cannot transmit the associated sensory data to the left hemisphere and its language centers. The left hemisphere perceives a change in the body's state, but does not know why - and so it "fills in" the missing details, fabricating a logical reason for the emotional reaction. This happens at a subconscious level, so that the person genuinely believes the verbal explanation they provide. In the language of psychology, this filling-in process of unconscious invention is called confabulation. But there is a significant implication to be drawn from these experiments. Clearly, these people's right hemispheres are aware of their environments, since they can generate the appropriate emotional response to a stimulus. But just as clearly, their verbal left hemispheres do not know some things that their right hemispheres do know. In short, these people's callosal disconnections have produced two separate consciousnesses - two distinct spheres of awareness - within their minds. There is an even more startling manifestation of callosal disconnection that supports this conclusion. Although the right hemisphere has no access to the language centers and therefore cannot speak, it can spell words by arranging block letters by touch. In one study of split-brain patients, a subject was asked what his ideal profession was. Verbally (i.e., using the left hemisphere), the patient responded that he would like to be a draftsman. However, with his left hand (i.e., using the right hemisphere), he spelled the words "automobile race" (Hock 2002, p. 8). As Andrew Newberg and Eugene D'Aquili say of results such as this: "Research shows that in such split-brain cases, the brain generates what seems to be two separate consciousnesses. Research on split-brain patients led brain scientist and Nobel laureate Roger Sperry to conclude, 'Everything we have seen indicates that the surgery has left these people with two separate minds, that is, two separate spheres of consciousness. What is experienced in the right hemisphere seems to lie entirely outside the realm of the left hemisphere.'" (Newberg and D'Aquili 2001, p. 22-23) An atheist is entitled to ask how this evidence can be reconciled with dualism. Clearly, in these split-brain patients, the different halves of their brain have access to different information and may even hold differing opinions. But under the soul hypothesis, this is much more difficult to explain. Presumably, the soul does not have its own internal information-sharing pathways that can be damaged or disconnected. If one part of the soul knows what is happening, all of it should know. If one part of the soul believes a certain thing, all of the soul should believe it. Descartes himself wrote that the soul was by nature indivisible, that it would not make sense to speak of "half a soul" (Feinberg 2001, p. 107). But the facts show that this is not the case. Alien Hand Syndrome The preceding two conditions both strike at the common-sense notion that each human being possesses a single, unified identity. Pure amnesia obliterates our sense of ourselves as continuous through time, chopping a person up into numerous evanescent selves, and the effects of callosal disconnection hint that there are multiple spheres of awareness lurking within our minds, which we usually do not notice because they normally communicate seamlessly with each other. Some experiments even seem to show that these spheres of awareness can have different desires from each other. However, there is another syndrome which demonstrates in a truly bizarre fashion that not only do these separate spheres of awareness exist, but that the divide runs far deeper than mere sensory perception. These discrete spheres within our brain can have different emotions and different thoughts - as is proven by the extraordinary condition called alien hand syndrome. In Stanley Kubrick's classic black comedy Dr. Strangelove, the title character is afflicted with a bizarre disorder - one of his hands will not obey him. It attempts to make Nazi salutes at inappropriate times, even tries to strangle him on occasion, and he is often forced to use his other hand to restrain it. It has been said that truth is sometimes stranger than fiction, but in this case, truth is equally as strange as fiction, because Dr. Strangelove's malady really does exist. "More than fifty years ago a middle-aged woman walked into the clinic of Kurt Goldstein, a world-renowned neurologist with keen diagnostic skills. The woman appeared normal and conversed fluently; indeed, nothing was obviously wrong with her. But she had one extraordinary complaint - every now and then her left hand would fly up to her throat and try to strangle her. She often had to use her right hand to wrestle the left hand under control.... She sometimes even had to sit on the murderous hand, so intent was it on trying to end her life." (Ramachandran 1998, p. 12) The obvious explanation was that she was mentally disturbed and doing this to herself, and indeed that was the diagnosis of several physicians who had previously examined her. But Dr. Goldstein found no signs of hysteria or other mental disorders - it genuinely seemed as if her left hand had a will of its own - and so he proposed a radically different explanation. He theorized that the woman's right hemisphere (which controls the left side of the body, including the left hand) had "latent suicidal tendencies" (ibid.) In a normal person, the more rational left hemisphere would inhibit these and prevent them from being translated into action; but if this woman had suffered damage to her corpus callosum, these inhibitory messages could no longer be transmitted to the other half of her brain, and the right hemisphere would attempt to act on its irrational self-destructive urges. Shortly after visiting Dr. Goldstein, the woman died (no, not from strangling herself). An autopsy confirmed the doctor's suspicions: she had suffered a stroke that had damaged her corpus callosum and severed the connection between the hemispheres, removing the brake her left hemisphere had put on the actions of her right. Today, additional data has backed up Dr. Goldstein's explanation. It is now known that the right hemisphere is mainly responsible for producing and mediating negative emotions, such as anger and sadness; patients with right hemisphere damage often lose the ability to feel these emotions and become inappropriately cheerful and euphoric (this will be discussed in more detail below). Startling as it may seem, the woman's callosal disconnection had revealed that there were two separate spheres of consciousness within her mind that felt and desired completely different things. One more question arises: If half this woman's brain had become suicidal, who or what was left over? What was the part of her that did not want to commit suicide and fought off the impulses of her "possessed" hand? The answer, of course, was her rational left hemisphere, disconnected from the right and so unaffected by the negative emotions it was churning out. Since the left hemisphere controls language, it - and she - was able to express shock and dismay over the irrational behavior of the other side of her body. But what this implies for normal people is that we - the part that we think of as "ourselves" - is only the left hemisphere. That is the part that creates a narrative to explain our actions and communicates with the rest of the world. But all the while, there is another, separate consciousness dwelling within our heads - the silent right hemisphere. Unable to control language, it cannot make its presence known directly, and in any case it usually communicates with the left so seamlessly that we do not perceive it as a separate entity. But when callosal damage brings this mute, watching presence to the surface, the results can be astonishing. Other cases of alien hand syndrome support this explanation. While this syndrome can happen in either hand, damage to the corpus callosum produces almost exclusively left alien hands. (Damage to the frontal lobes of the brain, which will be discussed in more detail later, can produce either a left or a right alien hand.) Furthermore, exactly as one would expect if AHS results from a disinhibition of the more emotionally volatile right hemisphere, alien hands are rarely helpful or pleasant. Instead, most of them perform actions ranging from the merely mischievous to the outright aggressive to the downright frightening. Frequently they do the opposite of what the consciously controlled hand intends. There are cases on record of alien hands that answer the phone and then refuse to surrender the receiver, that spill out drinks, that violently hurl objects at random. Sometimes a patient may open a drawer with his good hand only to have his alien hand close it; sometimes he may try to button up a shirt with one hand while the alien hand follows behind undoing the buttons. In one case on record, the alien hand attempted to tear up money (Feinberg 2001, p. 94-97). Most disturbing of all, some alien hands are genuinely violent. Strangling actions, as described above, do occur. In another case on record, Dr. Michael Gazzaniga describes a patient whose left alien hand grabbed his wife and shook her violently, while his right hand tried to assist her in bringing the left under control. On another occasion, the doctor was visiting the same patient, playing horseshoes with him in his backyard, when the patient's left hand reached out and picked up an ax leaning against the side of the house. "Because it was entirely likely that the more aggressive right hemisphere might be in control, I discretely left the scene - not wanting to be the victim for the test case of which half-brain does society punish or execute" (quoted in Feinberg 2001, p. 98). As the good doctor astutely noted, there would be a real problem of who was responsible if his patient's alien hand had followed through on its seemingly ominous intentions. But that problem would not be limited to merely mortal agents of justice. How would God judge such a case? The dualist must answer the question of how all of this is compatible with the existence of the soul. Do our souls reside only in our left hemispheres? Then who or what lives in the right? Or would dualists claim that the single, unified soul can somehow become fractured, split into two distinct consciousnesses, by damage to the physical brain? Paralysis and Denial Imagine that you are a doctor, making your rounds in the neurology wing of a hospital. You enter one of the rooms to check up on an elderly patient who recently suffered a severe ischemic stroke in the right hemisphere of his brain. Though he survived with the help of clot-busting drugs, it was too late to prevent damage from being done. The motor centers of his right hemisphere have been destroyed, and the patient is entirely paralyzed on the left half of his body. He will never stand or walk again, and will be confined to a bed or a wheelchair for the rest of his life. But thankfully, he seems to be in good spirits. He is taking the news extraordinarily well - perhaps almost too well - reacting to it with an incongruous lightness. You greet the patient and wish him a good morning. "How are you feeling?" you ask. "Fine," he says cheerfully. "Do you know why you're in the hospital?" you ask. The patient admits he had a stroke. "That's what the doctors told me, anyway. They did all their scans and X-rays. I guess I don't have any reason to doubt them." "But you're feeling fine now?" "Yes, fine," he agrees. Something is not quite right here; a suspicion is beginning to coalesce in your mind. It may upset this man, but you have to know, so you ask. "Can you walk?" "Of course I can," the patient says with a tone of mild petulance, as if he isn't sure why you're asking such a silly question. "And your hands? Can you use them?" "Of course." "Are they both equally strong?" "Yes, of course they are," he says nonchalantly. This man has not moved his left hand or stood up since his stroke; he has been in a bed or wheelchair since he arrived at the hospital. Though that terrible suspicion is essentially confirmed, you decide to push things just a bit further. "Can you touch your nose with your right hand for me?" you ask. He agrees and does so with no trouble. "What about your left hand?" you then ask. "Can you touch your nose with your left hand?" "Sure I can." The patient's paralyzed left hand does not move. "Are you touching it now?" "Yes, of course I am." His hand still has not moved. "Can you actually see yourself touching your nose with your left hand?" you ask. "Of course I can," he says in irritation. "It's right in front of my face." You decide to ask just one more question. "Can you clap your hands for me, please?" The patient looks at you in some puzzlement, but resignedly lifts his right hand and waves it in front of him, as if clapping it against an imaginary left hand. His real left hand lies where it is, completely paralyzed. (adapted from Ramachandran 1998, p. 128-129, where a virtually identical conversation occurs)* Few neurological disorders force us to confront the fragility of the sense of self more thoroughly than the condition called anosognosia. The Greek word basically means "unawareness of illness", and that is exactly what this syndrome is: a person who has suffered some severe, disabling injury yet remains steadfastly unaware - and vehemently denies if asked - that there is anything wrong with them. True anosognosia is not simple confusion; the patient literally cannot be convinced of the reality of their condition (Feinberg 2001, p. 21). Though anosognosia is most commonly associated with partial paralysis after a stroke, such as in the example above, it occurs in other conditions as well. Some sufferers of malignant brain tumors and other fatal conditions will steadfastly handwave away their doctor's diagnosis, insisting that they feel fine (Ramachandran 1998, p. 143). There is even an example on record of a patient who was unaware that he was blind (Heilman 2002, p. 133). What causes anosognosia? Advocates of dualism and others may contend that it is purely psychological, a Freudian defense mechanism employed by people facing a truth too terrible to accept. But other facts weigh against this explanation. First, stroke victims with anosognosia may deny their paralysis, but usually freely admit to other things wrong with them. As in the example above, they almost never deny that they did in fact have a stroke. Dr. Vilayanur Ramachandran tells us of a paralyzed patient with denial whom he offered candy if she could tie her shoelaces, only to have her chastise him, "You know I'm diabetic, doctor. I can't eat candy!" (Ramachandran 1998, p. 142) But much more important, and much more destructive to the Freudian theory, is that denial is almost exclusively associated with paralysis of the left side - in other words, with damage to the right hemisphere (Feinberg 2001, p. 51). Patients with left-hemisphere damage and right-side paralysis almost never experience denial, despite the fact that they would presumably have just as much psychological need for it. This strong association between denial and damage to a specific region of the brain suggests that something in that region is doing something critical for updating the mental image of one's own body. However, there is a third, very powerful piece of evidence - one that decisively rules out both the Freudian theory and dualism as well, and shows clearly how this bizarre disorder, as well as the sense of self in general, arises from and is inextricably unified with the functioning of our physical brains. In 1987, an Italian neurologist named Eduardo Bisiach performing tests on a patient with denial squirted cold water into her left ear, a test of the function of the nerves that control balance. But the experiment had an astonishing side effect: shortly after the test, when asked if she was paralyzed, the patient calmly replied that she had no use of her left arm! The mere injection of cold water in her ear had effected a complete, though temporary, cure of her denial. Dr. Ramachandran performed this experiment on another patient with the same condition and got the same astonishing result. He injected cold water into the ears of a patient with left-side paralysis who steadfastly denied her paralysis and insisted that both her arms were equally strong. Irrigating the right ear canal had no effect whatsoever; she continued to insist that she was fine. But when he tried irrigating her left ear canal instead: After [injecting the water], I asked again, "How are you feeling?" "My ear's cold." "What about your arms? Can you use your arms?" "No," she replied, "my left arm is paralyzed." That was the first time she had used that word in the three weeks since her stroke. "Mrs. Macken, how long have you been paralyzed?" She said, "Oh, continuously, all these days." (Ramachandran 1998, p. 145-146) Twelve hours later, one of his students repeated the questioning: "Do you remember Dr. Ramachandran?" "Oh, yes, he was that Indian doctor." "And what did he do?" "He took some ice-cold water and he put it into my left ear and it hurt." ..."What did he ask you?" "He asked me if I could use both my arms." "And what did you tell him?" "I told him I was fine." (p. 146) But this puzzle becomes even more complex. Sometimes denial is not permanent, but resolves itself spontaneously as the patient recovers. But what happens when such a patient is asked about their earlier denials? Dr. Ramachandran quizzed one: "Do you remember I asked you about your arms? What did you say?" "I told you my left arm was paralyzed." "Do you remember I saw you several times? What did you say each time?" "Several times, several times - yes, I said the same thing, that I was paralyzed." (Actually she had told me each time that her arm was fine.) "...Think clearly. Do you remember telling me that your left arm was fine, that it wasn't paralyzed?" "Well, doctor, if I said that, then it implies that I was lying. And I am not a liar." (p. 149-150) At this point it should be plain that this disorder goes far beyond any psychological defense mechanism; it even goes beyond a simple failure of the brain to update one's own body image. When a denial patient goes into remission, it seems as if they completely "rewrite their script" to make their past behavior compatible with their current knowledge of their paralysis. When the denial returns, their internal script is again rewritten in light of their renewed belief. It is as if, Dr. Ramachandran writes, "we had created two separate conscious human beings who were mutually amnesic", a "partial insulation of one personality from the other... even though they occupy a single body" (p. 146-147, emphasis added). So how can this strange condition - the division of a person into two selves, one aware of what has happened to them and one deluded, and each unaware of the other - be explained? Freudian theories, as already shown, will not suffice. Nor can theistic dualism hope to adequately explain this. If the soul stores our memories (a crucial component of identity and a requirement for continuity of consciousness - after all, aren't we supposed to remember our earthly lives when we get to the afterlife?), how can something so mundane as a squirt of cold water in the ear radically alter those memories? Even if some body defect prevents the information about the paralysis from reaching the soul - which is very unlikely, since these people can plainly see their limbs not moving, if nothing else - once it has reached the soul, how can it be so quickly lost again, as soon as the cold-water treatment wears off? On the contrary, only through materialism and the recognition that our mind is unified with, and at the mercy of flaws in, the physical brain can this phenomenon be satisfactorily explained. And a non-dualistic theory of the workings of the human mind can offer just such an explanation. Observing that anosognosia almost exclusively results from right-hemisphere damage, Dr. Ramachandran has proposed that the two halves of our brain serve two different roles in regard to our worldviews. His hypothesis is that the left hemisphere's job is to create a coherent perspective: to sort through the data it constantly receives from the senses and integrate it all into a consistent worldview. But when inconsistent data arrives - information that conflicts with what we already know or believe - it must be handled. One option, of course, is to completely tear down the existing belief structure and start over again; but if we did this for every minor discrepancy we encountered, it would be impossible to function in the world. Therefore, the left hemisphere functions as a preserver of the status quo, defending a person's belief system by discounting contradictory evidence or force-fitting it into the existing framework. The right hemisphere, by contrast, is hypothesized to be a "devil's advocate," searching for major inconsistencies and problems with the status quo and forcing a reevaluation of preexisting beliefs if enough inconsistencies turn up. (One possible explanation for why the cold-water treatment works is that it may stimulate nerves leading into the right hemisphere.) While it may be an oversimplification, this hypothesis is not without support. In a simple experiment using mirrors that created a discrepancy between what a test subject felt his arm doing and what he saw it doing, a region of the right hemisphere near the right parietal lobe lit up in a brain scan - regardless of whether the discrepancy occurred with the left or the right hand (p. 142). * This is a more severe form of denial. Not all people with the syndrome create such blatant confabulations; more commonly, they will give excuses or rationalizations why they're not walking or why their paralyzed arm isn't moving - they may say the limb is "lazy" or "a little tired" (Feinberg 2001, p. 21), or "It hurts to move that arm," or "The doctors have been testing me all day and I'm tired of it, so I don't want to move it" (Ramachandran 1998, p.129-130). Oppositely, on the most extreme end of the spectrum, some people with denial actually claim the paralyzed limb connected to their body belongs to someone else, a condition called somatoparaphrenia (p. 131). (Such people might say something like, "It's my brother's arm.") In all cases, however, these people will go to any lengths, rationalize away any contrary evidence or clutch at any explanation, no matter how strained, rather than admit the obvious. The potential relevance to theistic belief is interesting. Could it be that some fundamentalists and cult members have underdeveloped right hemispheres? (back) Capgras' Syndrome The disorder called Capgras' syndrome is "one of the rarest and most colorful syndromes in neurology" (Ramachandran 1998, p. 161). The sufferer, who is in every other respect perfectly rational and lucid, suddenly begins to insist that a close friend or loved one - a parent, a spouse, even a pet in some cases - has been replaced by an impostor who looks exactly like the missing individual. While this condition can occur spontaneously in those with schizophrenia or dementing illnesses such as Alzheimer's (Feinberg 2001, p. 33), it is often (about one-third of documented cases) found in people who have survived some sort of traumatic head injury. How can this condition be explained? The answer lies in the limbic system, a collection of structures deep within the brain that is responsible for emotional activation. When information from the eyes arrives in the brain, it is transmitted to the object recognition pathway of the temporal lobes to determine what a person is looking at - a face, a house, an animal - and that information is in turn relayed to the amygdala, the gateway to the limbic system, to determine the emotional significance of the object. If the object is the face of a loved one, the limbic system generates the appropriate emotional "glow" to let us know that it is indeed that person. But what if brain damage disconnects the pathway between the visual system and the amygdala? In that case, a person would still be able to recognize faces, but would not experience the emotions usually associated with them. In essence, the brain says to itself something like, "If this is my mother, why doesn't her presence make me feel like I'm with my mother?" (Ramachandran 1998, p. 162) - and the only way it can make sense of this discrepancy is to produce the Capgras delusion, assuming that the person merely resembles someone important to the viewer. It can be disconcerting to realize that emotions play such an important role in the process of judgment. One might well ask, why does this disconnection produce such a severe delusion? Even if the sufferer can't emotionally feel close to people, can't they still recognize them, at least intellectually? And under the doctrine of the soul, an immaterial rational consciousness not subject to the flaws of the brain, one might well expect this to be the case. But materialism lays to rest the common-sense notion of a "homunculus" - a little person living inside the brain, receiving its inputs and directing its actions like an air-traffic controller. We are our brains, and their defects are defects in our minds. But what does Capgras' syndrome have to do with a flaw in the sense of identity? As it turns out, this condition has some other, far more surprising side effects. The emotional "glow" produced by the limbic system does more than provide moment-by-moment recognition of significant faces. It turns out that this glow is a crucial component of forming and associating long-term memories. For example, suppose you go to the grocery store one day and a friend introduces you to a new person - Joe. You form a memory of that episode and tuck it away in your brain. Two weeks go by and you run into Joe in the library. He tells you a story about your mutual friend, you share a laugh and your brain files a memory about this second episode. Another few weeks pass and you meet Joe again in his office - he's a medical researcher and he's wearing a white lab coat - but you recognize him instantly from earlier encounters. More memories of Joe are created during this time so that you now have in your mind a "category" called Joe. This mental picture becomes progressively refined and enriched each time you meet Joe, aided by an increasing sense of familiarity that creates an incentive to link the images and the episodes. Eventually you develop a robust concept of Joe - he tells great stories, works in a lab, makes you laugh, knows a lot about gardening, and so forth. (Ramachandran 1998, p.169) But how does the brain link these disparate episodes together, recognizing that Joe is the same person each time? As an analogy, say the brain's memory, in the abstract, functions like a computer file management system. Every time you encounter someone, a new "file" of memory is created. How does the brain know that these new files belong in the same previously created "folder" together with earlier memories of the same person? The answer lies in the limbic system. The emotional glow it generates apparently functions as a sort of thread running through these disparate memories and tying them together, letting the brain know that they belong together in the same "folder". But what if this glow is