Appendix B

Naturalistic Explanations and Why They Fall Short

A Reference Survey of the Brain-Based Theories and Their Limits

A man has a cardiac arrest in a hospital room. His heart stops. Within seconds, the blood flow to his brain shuts down, and his EEG goes flat. By every medical measure, his brain is offline. And yet, when the team brings him back, he describes in detail the instruments they used, the words they spoke, and the color of the nurse’s shoes. He is calm, certain, and unshaken. He says the experience was more real than anything he has known.

How do you explain that?

For decades, researchers who hold a purely physical view of the mind have offered a range of theories. Each one tries to show that the brain, even a dying brain, can produce the vivid, ordered, sometimes verifiable experiences we call near-death experiences. These theories deserve a fair hearing. The researchers who proposed them are serious people doing serious work. Some of their observations are correct as far as they go. But as I have studied these explanations alongside the evidence, I have found that every one of them breaks down at the same point. None of them can account for the cases where dying patients accurately described things they had no natural way of knowing.

This appendix is a reference survey. It is meant to sit alongside Chapter 24, which carries the full argument. Here I want to give you a quick, clear look at each explanation: what it claims, what it can explain, and where it fails. If you are talking with a friend or reading a skeptical article and you want to check a specific theory, this is the place to turn.¹

Oxygen Starvation (Hypoxia and Anoxia)

The claim. When the brain runs short of oxygen, it misfires. The resulting confusion and hallucinations produce the tunnel, the light, and the other features of an NDE. This is probably the oldest and most common explanation offered by skeptics.²

What it explains. Oxygen loss does affect the brain. That much is well established. Patients who lose oxygen can experience tunnel vision, strange visual effects, and altered states of awareness. The theory has a foothold in real physiology.³

Where it fails. The clinical effects of oxygen deprivation look nothing like an NDE. Carter documents the history: in lab experiments where subjects were gradually deprived of oxygen, performance became increasingly inept until they lost consciousness. In thousands of such experiments on thousands of people, no one ever reported an NDE.⁴ The medical record is clear. Oxygen loss produces confusion, mental laziness, irritability, and memory failure. NDEs are the opposite: heightened alertness, clear and structured perceptions, overwhelming peace, and memories so vivid they last a lifetime. The symptoms of oxygen deprivation and the features of NDEs run in opposite directions.⁵

Greyson makes the point from the clinical data. Research that actually measured oxygen levels during medical crises consistently showed that NDEs are associated either with higher oxygen levels or with levels the same as those of patients who did not have NDEs. No study has ever shown decreased oxygen during an NDE.^5b

Michael Sabom made the same point from his years of cardiology research. In the G-LOC experiments, where fighter pilots were pushed to the edge of oxygen loss in centrifuges, the resulting “dreamlets” were confused, fragmentary, and quickly forgotten. Nothing like a classic NDE appeared. The researcher who ran those tests, Dr. James Whinnery, concluded that the features unique to NDEs are beyond what oxygen deprivation alone can produce.⁷

Carbon-Dioxide Buildup (Hypercarbia)

The claim. When the body stops circulating blood properly, carbon dioxide builds up. Elevated CO₂ levels can alter brain function and trigger unusual experiences, including a sense of bright light and detachment.⁸

What it explains. Some studies have found a loose connection between higher CO₂ levels and certain NDE-like sensations. The theory draws on real chemistry.

Where it fails. The connection is inconsistent. Many NDE patients had normal CO₂ levels, and many patients with dangerously high CO₂ had no NDE at all. And as Carter emphasizes through neuropsychiatrist Peter Fenwick, a cardiac arrest will certainly cause CO₂ to build up, but that buildup will always be accompanied by oxygen loss, which brings its own disorientation and confusion. In Fenwick’s words, a failing brain produces experiences that are limited, confused, and disorganized; the very opposite is true of the NDE.^8b Bruce Greyson has noted that this theory cannot explain why only a fraction of cardiac-arrest survivors report NDEs, since they all experience the same buildup of carbon dioxide.⁹

Carter points to a decisive case from Sabom. A cardiac-arrest patient whose blood gases were monitored during resuscitation reported a vivid NDE with confirmed perceptions, including a description of the blood draw from his groin. When the lab results came back, his arterial oxygen was well above normal and his carbon dioxide was actually lower than normal. Neither anoxia nor hypercarbia was present at the moment of the experience.^9b And like the oxygen theory, the CO₂ theory faces the core problem. A chemical change in the blood might trigger an experience. It cannot explain how the patient accurately described events down the hall while the brain was not working.

DMT, Endorphins, and Ketamine-Like States

The claim. The dying brain releases a flood of natural chemicals. Endorphins produce the feeling of peace and calm. DMT (dimethyltryptamine), a compound found in tiny amounts in the brain, may produce the vivid visions and the sense of entering another world. Ketamine, an anesthetic, has been shown to produce some NDE-like features, and the brain may release similar compounds at death.¹⁰

What it explains. There is no question that brain chemicals shape experience. Endorphins do ease pain and create calm. Ketamine users sometimes report tunnel-like visions and out-of-body sensations. The theory draws on real pharmacology, and it may well explain some of the emotional tone of NDEs, such as the deep peace and the absence of pain.¹¹

Where it fails. Carter identifies the core weakness of the ketamine model: it rests on two crucial assumptions, neither proven. First, that the brain produces a chemical similar to ketamine under the stress of dying. Second, that ketamine experiences strongly resemble the NDE. But the effects of ketamine depend greatly on set and setting, producing a wide range of reactions; NDEs are surprisingly similar regardless of cause or circumstances.¹¹

The deeper problem is one that neuropsychiatrist Peter Fenwick raises plainly, as Carter records: any physician dealing with head injury, epilepsy, or altered cerebral physiology knows that as cerebral function becomes compromised, it becomes disorganized. Acute cerebral catastrophes result in confusion and not clarity. Fenwick concludes that although ketamine may produce experiences similar to the NDE, this does not explain how those same experiences can arise in a brain that is shutting down.^11b

No drug, no matter how powerful, gives a person accurate knowledge of events they did not witness with their physical senses. In my research, I found 1,618 cases that met the criteria for “Exceptional” or “Strong” evidence that consciousness was working apart from the brain. Many of those cases were confirmed by medical professionals.¹³ A chemical flood inside a dying brain cannot reach outside that brain to observe a shoe on a window ledge three floors up. It cannot describe a surgical instrument hidden from view. The veridicality gap is the problem, and the drug theory does not touch it.¹⁴

As for DMT, no study has shown that the human brain releases it in the amounts needed to produce an NDE. No one has shown it is released at the time of death at all. The theory remains a hypothesis without firm support.¹⁵

Temporal-Lobe Activity

The claim. The temporal lobes of the brain process sensory input, emotion, and memory. Seizures or electrical stimulation in the temporal lobes can cause vivid visual hallucinations, feelings of deep meaning, memory flashbacks, and even the sense of being outside one’s body. Some researchers have proposed that a dying brain’s temporal lobes fire in ways that produce the full NDE. Neuroscientist Michael Persinger famously used a device called the “God helmet” to stimulate the temporal lobes and claimed to produce NDE-like experiences.¹⁶

What it explains. Stimulating the temporal lobes does produce some NDE-like features in a lab setting. Feelings of a “presence,” flashes of memory, and altered emotional states have been reported. The overlap is real, though limited. But as Bruce Greyson points out, patients whose brains are being stimulated describe these sensations as unrealistic, dreamlike events, not as things that are really happening, whereas people describe their NDEs as undeniably real. It is a bit like watching a war movie compared with actually fighting in a battle.^16b

Where it fails. There is a basic problem with the seizure version of this theory. A seizure requires chaotic, high-amplitude electrical activity in the brain. A cardiac arrest produces the opposite: brain silence. Within ten to twenty seconds after the heart stops, organized brain activity drops to zero on the EEG.¹⁷ The most evidentially strong NDEs happen during cardiac arrest, precisely when seizure activity can be ruled out. The brain cannot have both a seizure and no electrical activity at the same time.

Sabom tested this directly in the case of Pam Reynolds. During her surgery, her brain waves were watched the entire time. No seizure phenomena were detected. Her auditory brainstem responses were absent. No blood was flowing through her brain. By every clinical measure, her brain was dead. And yet she reported the deepest NDE in his entire study, with details later confirmed by the surgical team.¹⁸

As for the “God helmet,” Carter documents that Persinger’s own published table of 153 subjects showed that the most common experiences were dizziness and tingling, not NDE features. In 2004, a Swedish team at Uppsala University attempted to replicate Persinger’s results under proper double-blind conditions, using equipment borrowed from his own lab. They found no effect from the magnetic fields whatsoever. The only thing that predicted strange experiences was the subject’s personality: those rated “highly suggestible” reported unusual sensations whether the helmet was on or off. Carter concludes that the well-established psychology of suggestion, not magnetic stimulation, was the best explanation for Persinger’s original results.¹⁹

REM Intrusion

The claim. Neurologist Kevin Nelson proposed that NDEs result from REM sleep states intruding into waking consciousness. In REM intrusion, the brain’s dreaming machinery activates while the person is awake or nearly so, producing dream-like experiences that feel intensely real.²⁰

What it explains. REM intrusion is a recognized phenomenon. People who experience it can report vivid imagery, a sense of paralysis, and a conviction that what they saw was real. The theory offers a plausible mechanism for some of the subjective vividness of NDEs.

Where it fails. Greyson examined Nelson’s study and found that the rate of REM intrusion symptoms in NDErs was no higher than the rate in a random sample of the general public. The study did not show what it claimed.^20b Many NDEs occur under general anesthesia, which suppresses REM. Measurements of REM activity in NDErs show it is actually lower than in other people, not higher. And an Italian research team found that NDErs remembering their experiences had brain wave patterns typical of real memories, not fantasies or dreams.^20c

Dreams, even vivid ones, do not contain accurate information about the external world that the dreamer had no access to. You may dream of a hospital room, but you will not dream the exact words spoken by a nurse three doors down and then have those words confirmed. REM intrusion also cannot explain the remarkable consistency of NDE features across cultures, across age groups, and across seven decades of reported cases. In my research, I found that core NDE features held steady before and after 1975, when Raymond Moody’s book first brought NDEs to popular attention.²¹ Children too young to have absorbed cultural scripts report the same core elements as adults (see Chapter 11). If NDEs were dreams shaped by expectation, the features should shift with the culture and the decade. They do not.²²

Expectation and Prior Knowledge

The claim. People have heard about NDEs from books, movies, television, and conversations. When they come close to death, their brains draw on this stored information and construct an experience that matches the cultural script. The NDE is, in short, a self-fulfilling prophecy.²⁴

What it explains. Cultural context does influence how people describe their experiences. That much is fair. A person who has read about NDEs may use familiar language when describing what happened to them.

Where it fails. If cultural expectations produced NDEs, we would expect to see wide variation across cultures and across time. We do not. The core features are remarkably stable. We would also expect children to have different experiences from adults, since they have less exposure to the cultural script. They do not. My research included 982 childhood NDEs, with 717 from children under thirteen. The core elements were the same as in adult cases.²⁵

The expectation theory also stumbles over timing. If patients were constructing memories after the fact, based on overheard conversations or guesses, the earliest-documented cases should be the weakest. Instead, cases documented within twenty-four hours of the event, or even before the patient was told what had happened, contain the strongest and most accurate perceptions. In my dataset, fifteen “gold standard” cases were documented before any outside information reached the patient. The account was on record before it could have been contaminated.²⁶

The Dying-Brain Electrical Surge

The claim. Studies in animals (and a small number of human cases) have detected brief surges of electrical activity in the brain in the moments after cardiac arrest. Some researchers suggest that this surge could produce the vivid experiences reported in NDEs.

What it explains. The surge is real. It has been measured in rats and in a handful of human patients. Parnia documents the trail of discovery: in 2009, intensive care physician Lakhmir Chawla first detected unexpected surges of electrical activity after death in seven patients. In 2013, Jimo Borjigin found a surge of gamma oscillations in dying rats. In 2022, neurosurgeon Ajmal Zemmer found bursts of gamma waves in the brain of an eighty-seven-year-old man thirty seconds before and after his heart stopped. The evidence shows that the brain does not simply go dark at the moment of death; there may be a brief burst of activity on its way down.²⁷

Where it fails. A burst of electrical activity is not the same thing as organized perception. Parnia’s own AWARE-II study, the largest of its kind, followed 567 cardiac-arrest patients across twenty-five medical centers, attaching brain monitors during resuscitation. The brain flatlined after the heart stopped, but normal electrical markers, some suggestive of consciousness, emerged even up to an hour later. Parnia’s team concluded that the nonfunctioning brain had not degenerated but had entered something like a hibernation state. As Chawla put it, there was no blood flow and no oxygen going to the brain. If this were merely a dream or hallucination, the brain would require blood flow and oxygen to produce it.^27b

George Mashour, a colleague of Borjigin at Michigan, stressed that what the researchers recorded was coordinated gamma-frequency activity, not the brain going haywire. The AWARE-II team went further still. They concluded that the mind and consciousness, tethered to the brain in death, are interacting with and modulating the brain, not the other way around.^27c And the surge theory still does not explain the cases where veridical perception occurred during documented flat-line EEG recordings, well after any such surge would have ended. In my research, sixty-six cases occurred during a confirmed flat EEG with monitoring in place.²⁸

Depersonalization

The claim. Depersonalization is a psychological defense mechanism. When the mind faces extreme trauma or the prospect of death, it detaches from the body to protect itself. The out-of-body experience reported in many NDEs is simply this detachment in action.

What it explains. Depersonalization is a well-documented response to trauma. People who experience it report feeling detached, as though watching themselves from outside. The emotional tone is flat and dreamlike. In that narrow sense, there is a surface resemblance to the out-of-body component of an NDE.

Where it fails. This detachment is vague, flat in feeling, and lacking in detail. It does not produce the hyper-real clarity, the overwhelming peace, or the structured encounters reported in NDEs. And most critically, depersonalization does not give a person access to information they could not have known. People who dissociate under stress do not accurately describe events in other rooms or identify objects hidden from view. The veridical component, once again, is the gap this theory cannot bridge.

Memory Error and Confabulation

The claim. Human memory is unreliable. After a crisis, the brain reconstructs events, fills in gaps, and builds a story that may feel real but is partly or wholly invented. NDEs are simply an extreme case of this ordinary process. Susan Blackmore argued that the out-of-body experience is a model the brain builds from memory and imagination when normal reality breaks down.²⁹

What it explains. Memory errors are real. People do confabulate. Eyewitness testimony is not always reliable. Skeptics are right to raise this caution, and NDE researchers take it seriously.

Where it fails. Blackmore predicted that people who had out-of-body NDEs should be those who naturally use a “bird’s-eye view” in their dreams and imagination. Sabom tested this directly. When he asked forty NDErs about their dreaming habits, 73 percent said they experienced their dreams as participants, not as observers looking down. There was no difference in dreaming style between those who had out-of-body NDEs and those who did not. Blackmore’s prediction failed.³⁰

The confabulation theory also cannot explain the cases where NDE accounts were documented early, before the patient could have been influenced by conversations, media, or the passage of time. My research found 1,350 cases documented within twenty-four hours of the event, and those accounts were not weaker or vaguer than accounts recorded later. They were among the strongest.³¹

Carter records a striking observation from Peter Fenwick. In his large-scale study, Fenwick found head-injury patients whose waking state showed the dense confusion expected after a severe blow. Memory for the accident and the confused awakening was absent. And yet, within that gap, the patients had full memory of a wonderfully clear NDE. Fenwick concluded that no current understanding of cerebral functioning can explain how a brain in dense unconsciousness could structure and remember a clear, comprehensive experience.^31b

The memories hold over time, too. Greyson readministered a questionnaire to seventy-two NDErs an average of almost twenty years after their original responses and found no significant alteration. NDE memories do not drift, embellish, or fade the way confabulated memories do.^31c

The Rock They All Break On

Every theory I have surveyed here has the same shape. It identifies a real brain process, maps it onto one or two features of the NDE, and says: “There. That explains it.” And for the subjective features, the peace, the tunnel, the sense of detachment, these theories sometimes have something useful to say. I do not dismiss that.

But none of them can explain the verified cases.

In my doctoral research, I analyzed 5,278 near-death experiences. Of those, 1,618 met the criteria for “Exceptional” or “Strong” evidence that consciousness was operating apart from the physical brain. In 1,114 cases, the person accurately observed things happening at a distance from their body. In thirty-three cases, blind people reported verified sight. In sixty-six cases, the NDE occurred during a documented flat EEG, meaning no measurable brain activity was taking place at all.³³

No oxygen theory can explain this. No chemical theory, no seizure theory, no dream theory, no memory theory, and no electrical surge theory can either. None of them can explain how a person with no brain activity accurately described events they did not witness with their physical senses. That is the rock every naturalistic explanation breaks on. (For the full cases, see Chapter 9. For the full argument against the dying-brain view, see Chapter 24.)

I want to be fair. Future research may reveal things we do not yet know about the brain. I do not claim that the absence of a current explanation proves the existence of the soul. That would be a hasty argument. But I do claim this: the evidence we have right now points clearly toward one conclusion. Consciousness can operate apart from the brain. Thousands of cases with strong documentation support this. The best explanation, and the one most consistent with Scripture, is that we are more than our bodies. The soul is real, and it survives.

The psalmist wrote that we are “fearfully and wonderfully made” (Psalm 139:14). The deeper the researchers look into what happens at the border of death, the more that verse rings true. We are not merely matter in motion. We are body and soul, held together by the God who made us, and the evidence from the edge of death keeps pointing us home.