by Stephen Cave
That people sometimes experience such things as traveling down a tunnel of light is not disputed. The popular perception of such experiences is, however, skewed: many people are not aware, for example, that the classic case described above forms only a minority of such experiences, which vary greatly in detail and intensity and do not occur only when a patient is near death. Indeed, experiences much like an OBE can be induced by certain drugs or by electrodes stimulating part of the brain. Attempts have therefore been made to test the veracity of claims to be floating outside the body—for example, by putting up signs in emergency rooms that could be read only from a vantage point above the patient. So far, no hard evidence of a person genuinely leaving his or her body has resulted.
In order to conclude that the existence of souls really is the best explanation for out-of-body experiences—or for haunted houses, or for a Tibetan child choosing one rosary over another—we would first need a plausible account of what the soul is and how it could survive the body. Given the ambiguity of the evidence, without a strong theory of the soul a naturalistic explanation is likely always to be preferable. This therefore brings us to the case for the second argument: for the soul as mind.
Although large numbers of people today profess belief in a soul, many are vague when pressed on exactly what they think it is. But if the soul is to be your vehicle to immortality, then it must capture some fundamental essence—the real you—such that if your soul lives on after the death of your body, you can be assured that you live on. In the West, this “real you” is usually taken to mean your mind—that conscious part of you that thinks, feels, remembers, dreams. When you float out of your dying body or arrive in heaven, you expect at the very least to have conscious awareness and intact memories and beliefs.
The case for the existence of the immortal soul therefore rests upon the mind being independent of the body and dependent instead upon some spiritual essence that can survive bodily death. If, on the other hand, the mind is entirely dependent on the body, then we would have to conclude that the mind dies when the body dies, and there would then be little of us left over to call the soul. The crucial question for the plausibility of the Soul Narrative is therefore whether your mind or consciousness can, like the captain of a sinking ship, leave your dying body to continue its existence, or whether, as one of Socrates’s skeptical friends put it, your mind ceases with the destruction of your body just as the music of a harp ceases with the destruction of the harp. Let us consider the evidence.
THE doctrine of the soul stems from a time before the insights of modern science, when philosophers (Aristotle, for example) believed that the brain was nothing more than an elaborate cooling mechanism for the blood. The body seemed a crude and unreliable construction—clay roughly molded by the gods. It seemed inconceivable that this matter could be responsible for the richness of memory, the mystery of creative thought or the profundity of religious sentiment. Much more rational instead to attribute the glory of the human mind to the soul, the divine spark, than to the workings of the overcooked-cauliflower-like object in our skulls.
Nonetheless, some thinkers—including Aristotle—were skeptical about the mind outliving the body. We have seen that early Jews and Christians also believed immortality could only be granted through the reassembly of the complete man or woman, flesh and all. As science and medicine advanced, evidence for a very close relationship between mind and brain grew. The mischievous skeptic Voltaire, for example, said that he could not help laughing when told that a person’s mental faculties could outlive their brain—a response most unwelcome in the Catholic France of the 1730s. In a treatise first published after his death, he wrote that “as God has connected the ability to have ideas to a part of the brain, he can preserve this faculty only if he preserves this part of the brain; for preserving this faculty without the part would be as impossible as preserving a man’s laugh or a bird’s song after the death of the man or the bird.”
Some of the most compelling early evidence for the dependence of the mind on the brain came from cases of people with brain damage. Probably the most celebrated is that of Phineas Gage, a railway foreman working in the U.S. state of Vermont. A large part of the front of his brain, called the left frontal lobe, was destroyed in 1848 when a metal pole was forced by an explosion through his cheek and out the top of his head, landing some eighty feet away. Remarkably, Gage survived and physically made a full recovery. But more remarkably, at least to the scientific community of the time, the accident altered Gage’s personality in surprising and dramatic ways. Whereas previously a responsible, diligent and respected worker, he is said to have become “capricious,” “fitful” and “irreverent,” unable to hold down a steady job. A localized brain injury seemed to have caused a change in Gage’s moral character, a part of his personality about as closely associated with the God-given soul as any could be.
We do not in fact have enough details about the Gage case to draw substantive conclusions from it alone. But fortunately we don’t have to: both the capacities of medicine to keep alive people with brain damage and of science to systematically study such cases have increased exponentially in the intervening decades. The result is a wealth of data on how injuries to particular parts of the brain can eliminate or substantially alter core aspects of the mind. It is now well documented how specific brain injuries can, for example, destroy a person’s capacities for emotion, memory, creativity, language and, as in the Gage case, respect for social norms and decision-making, as well as a person’s ability to process sense perceptions such as sight and sound. All these are model examples for faculties that would previously have been attributed to the soul. The crux of the challenge is this: those who believe that the soul could preserve these abilities after the total destruction of the brain in death must explain why the soul cannot preserve these abilities when only a small portion of the brain is destroyed.
To make this point clear, we can take the example of sight. If your optic nerves in your brain are sufficiently badly damaged, you will no longer be able to see—you will go blind. This tells us very clearly that the faculty of sight is dependent upon functioning optic nerves. Yet curiously, when many people imagine their soul leaving their body, they imagine being able to see—they imagine, for example, looking down on their own corpse or on their own funeral procession. They believe, therefore, that their immaterial soul has the faculty of sight. But if the soul can see when the entire brain and body have stopped working, why can’t it see when only the optic nerves have stopped working? In other words, if blind people have a soul that can see, why are they blind?
This question has no satisfactory answer, and indeed some thoughtful theologians, such as Thomas Aquinas, have accepted that a soul without a body cannot see—seeing is something done by a body and brain with eyes and optic nerves in working order. But we now know that, just as damage to the optic nerve can destroy the faculty of sight, so damage to other parts of the brain can destroy faculties like memory and reason. Increasingly, evidence suggests that all aspects of the mind and personality are in this way dependent upon the brain. So, paralleling our question about the blind person, we can ask of someone with brain damage who is unable to think rationally or feel emotions: If they actually have a soul that is able to think rationally or feel emotions, why can’t they think rationally or feel emotions? Why would localized brain damage stand in the way when destruction of the whole brain and body does not?
FOR a long time, students of the brain were limited to Gage-style cases. But in the past decades, a wholly new technology has revolutionized neuroscience: machines that can produce images of the living brain in action. Collectively, the techniques involved are known as “neuroimaging,” and they enable scientists to closely study the correlations between the airy world of thought and the measurable, physical matter of the brain. In laboratories around the world, you can now watch live as various parts of your cerebrum light up when you engage in such typically mental activities as remembering your m
other’s face, imagining playing tennis or simply daydreaming.
The results show that for every mental process, there is an accompanying brain process. Even more worrying for the Soul Narrative, they show that the physical brain process starts before the conscious mind is aware of it. So, for example, someone monitoring your brain activity could tell you which decision you have made (left or right, tea or coffee or whatever) before you even consciously know yourself. This makes no sense at all if the real you is a conscious soul. But it makes perfect sense if your mind is the product of the workings of a complex, physical brain.
In a way, of course, we are all aware of the intimate link between mind and brain: alcohol, for example, gets us drunk, substantially affecting our attitude to risk, respect for social norms and many other aspects of our personality. But alcohol is simply a physical substance; if our minds were dependent on a nonphysical soul, why would they be so radically altered by a particular molecule of carbon, hydrogen and oxygen? Similarly, we know that even a cup of tea or coffee can affect our mental states, not to mention drugs such as heroin and cocaine. Even the level of water in our bodies can affect our personalities. Neuroscience, along with a better understanding of our underlying biology, is beginning to explain these intimate bonds between mind, body and brain.
The world-renowned neuroscientist Antonio Damasio illustrates this with the example of hunger. He writes, “Several hours after a meal your blood sugar level drops, and neurons in the hypothalamus detect the change; activation of the pertinent innate pattern makes the brain alter the body state so that the probability for correction can be increased; you feel hungry, and initiate actions to end your hunger.” Some of the actions you take to end your hunger might be unconscious, such as reaching for another cookie without thinking about it, and others may be conscious, such as deciding what to choose from a menu or following a recipe in a cookbook. But all those mental processes are themselves just part of the larger loop of biochemical activity that began with the drop in blood sugar levels.
What happens if your blood sugar level drops too low illustrates even more clearly the union of mental and physical: First, you will begin to feel anxious and become irritable, and your ability to concentrate—at least on anything not food related—will diminish. As diabetics know, if it suddenly drops lower still, you can become emotionally volatile, belligerent and confused. If, on the other hand, your hunger is prolonged, then you will eventually become apathetic and depressed. These are all profound changes to your personality—the part of you that is supposed to be the province of the soul—caused by chemical changes in the brain and body. Under the close scrutiny of modern science, the ancient distinction between mental and physical breaks down, and thought and feeling appear firmly grounded in biology.
CAN MATTER THINK?
THE main argument for believing that a mind requires a soul is that it is difficult to see how the fine and ethereal world of thought could arise from crude matter alone. Those who make this argument—known as dualists—maintain that mental events like remembering and dreaming are fundamentally different in kind to the workings of physical things such as brains. Physical things can, for example, be measured, weighed and located, but not so your memory of your first kiss or your dream of a place in the sun. Physical things are observable to all, whereas mental processes seem to have an irreducibly subjective quality—only you know what it is like to be you. Summing up this view one hundred years ago, the Catholic Encyclopedia asserted that “the chasm that separates psychical facts from material phenomena is intellectually impassable. Writers, therefore, who make thought a mere ‘secretion of the brain’ … may be simply ignored.”
A century ago and earlier, such arguments were conducted largely in seminaries and colleges, on the basis of abstract principles. Even then, not all were convinced by the claim that only a soul could explain the mysteries of the mind. Thomas Jefferson, for example, third president of the United States and all-around Enlightenment man, wrote that he should “prefer swallowing one incomprehensibility rather than two. It requires one effort only to admit the single incomprehensibility of matter endowed with thought, and two to believe, first that of an existence called spirit, of which we have neither evidence nor idea, and then secondly how that spirit, which has neither extension nor solidity, can put material organs into motion.”
Note that Jefferson is not denying that it is mysterious how “matter” such as a brain can produce thought. Rather, he is saying that the alternative soul-based view is even more mysterious: First, it requires us to accept the existence of some nonmaterial, spiritual stuff that can produce the conscious mind. No evidence is given by the soul theorists for this stuff’s existence, nor an explanation for how it produces thought. It is taken to be obvious that spiritual stuff can secrete consciousness in a way that material stuff cannot. But this is not obvious—certainly no more obvious than how the brain could produce consciousness.
Second, Jefferson is pointing out that if we accept a soul-based explanation of the mind, we must additionally explain how this spiritual stuff can seamlessly interact with and control the physical body. When you make a decision to get up, your body usually responds by getting up—a manifestly physical event. But how does an entirely nonmaterial thing move around the atoms, molecules and cells of the brain and body in order to cause this physical event? If the mind is itself part of the physical brain, this is much less mysterious.
Such theoretical considerations have, as we have seen, now been supplemented by the evidence of neuroscience. Unlike Jefferson and the authors of the Catholic Encyclopedia, we can begin to appreciate the true magnificence of the human brain. Each one of us has in our skulls somewhere in the region of one hundred billion neurons, each of which in turn has on average seven thousand synaptic connections to other neurons. It is no surprise that we cannot envision how the brain produces the conscious mind, because such complexity is indeed quite literally far beyond anything we can imagine. It is not an exaggeration to say that the human brain is the most complex thing in the known universe. If this hugely intricate system involving trillions of connections forming millions of interconnected networks is not producing our minds, then we might wonder just what it is doing.
FOR the idea that your personality might survive your bodily death the situation therefore looks hopeless. This is not to say that all the mysteries of mind and brain have been solved; they have not. Neuroscience is still in its infancy, and there is a great deal about the intricate workings of the brain and the production of the conscious mind that is not yet understood. Perhaps indeed we will never properly understand how the mind arises. But all of the now-voluminous evidence so far accumulated points to the complete dependence of the mind on the body. The psychologist Jesse Bering sums it up so: “The mind is what the brain does; the brain stops working at death; therefore, the subjective feeling that the mind survives death is a psychological illusion operating in the brains of the living.”
That illusion is of course generated by the Mortality Paradox. It is a testament to the success of the Soul Narrative in resolving this paradox and assuaging our fear of death that it remains so popular in the Western world despite the evidence of science. Nonetheless, in particular in Europe, this belief is thought to be on the decline (though accurate figures for earlier periods are hard to come by). Not so in India, for example, where religiosity remains high. But as we saw earlier, the Hindu and Buddhist ideas of the soul are abstracter and leaner than those of the Abrahamic religions common in the West. In particular the Buddhists strictly reject the idea that the entire personality, complete with memories, beliefs, dreams and dispositions, survives bodily death; this they have long believed to be dependent on the body.
When the Dalai Lama met with leading neuroscientists in 1989 for a symposium to discuss the implications of brain science, he explained, “Generally speaking, awareness, in the sense of our familiar, day-to-day mental processes, does not exist apart from or independent of the brain, acc
ording to the Buddhist view.” The soul in the Western sense of an independent entity that supports the full personality, he accepts, is “thoroughly refuted.” But Buddhists do believe in some essential part of you that survives the body in order to be reincarnated in accordance with the laws of karma. This is pure consciousness, stripped of all memories and convictions and the rest of the accumulated baggage of a lifetime. The Dalai Lama describes it as a “continuum of awareness that … does not depend upon the brain.” Can this pared-down soul, this “continuum of awareness,” survive the onslaught of neuroscience?
KNOCKING THE SOUL ON THE HEAD
THERE is one big problem with the idea that your consciousness or “awareness” can in some form survive the death of your body. It is something with which we are all in fact very familiar, not least from countless Hollywood films: simply that if you get hit on the head with sufficient force, you will be knocked unconscious. Your awareness of the world ceases; your lights go out. The hitting is itself a physical act, with measurable, physical effects on the brain, and its result is that your consciousness is temporarily extinguished. Similarly, if you are injected with general anesthetic—a syringe full of chemicals—your awareness will be extinguished. For anyone who thinks consciousness can survive bodily death, this is an embarrassing state of affairs.
The reason is this: the soul, which even in its pared-down form is supposed to maintain some minimum degree of consciousness, is supposed to be an entirely nonmaterial thing independent of the body—only thus can it survive the body’s death. Now it is natural to suppose that a hard blow to the head would stop your body from working—we might expect you to collapse to the ground and even to seem, from the outside, unconscious. But if consciousness were being maintained by an entirely nonmaterial thing, we would expect your consciousness to continue regardless. If you have a nonmaterial soul, you should, after the ordeal, be able to tell us how frustrating it was that your body had stopped working and what you thought while you were waiting for your body to recover. But this is not what happens.