As long as the nature of consciousness will remain a mystery, we will be in the grip of anxiety. And that is because we are, all of us, haunted by that uniquely human question: what awaits us after death?
Although the vast majority of Americans believe in some sort of afterlife, such beliefs are starkly at odds with what neuroscientists know, which is that consciousness is created by the brain and dies with the brain.
How can we be so sure of this, given that the nature of consciousness isn’t yet well understood? The reason is this: the little we do know assures us that the particular character of consciousness depends on very particular brain processes.
For example, if certain brain areas are changed or damaged, the very nature of your conscious experiences can be fundamentally altered. The medical literature abounds with various brain disorders that impact how we experience the world. These include cerebral achromatopsia (caused by damage to the ventral occipitotemporal cortex), which makes you unable to perceive color; or akinetopsia (due to damage to a part of visual cortex called V5), which makes you unable to perceive motion; or prosopagnosia (due to damage to a brain area called the fusiform gyrus), which makes you unable to perceive faces; or cortical deafness (due to damage to auditory brain centers), which makes you unable to hear; or anterograde amnesia (due to damage to a brain structure called the hippocampus), which makes you unable to form new memories.
Many of these brain disorders go far beyond changing your conscious experiences in the “now”: they also terminate your ability to remember, imagine, or even dream of what it would be like to experience a particular sense. For example, in the case of cerebral achromatopsia, the very notion of color is wiped off the map of things you can conceive of. Color becomes as foreign to you as a bat’s ability to echolocate.
The reason that damage to certain brain regions can have such effects is simple: these brain areas are responsible for producing conscious experiences. We don’t yet understand how these brain areas produce conscious experiences, but we know that they do it. Unlike sensory organs like the eyes and ears – which convey information to these brain regions – these parts of the brain are actually doing the job of perceiving. If you lose your eye, you will be blind, but you will remember color. If you lose your ventral occipotemporal cortex, you will be blind to both the experience and to the memory of color.
The same logic applies to personality. If you damage or change certain parts of the brain involved in determining personality, then the way you behave – the very kind of person you are – will be fundamentally and irreversibly altered. This much is attested by the dramatic behavioral effects of accidental brain trauma or lobotomies.
My principle claim – that conscious experience depends entirely on the brain – is also supported by research involving direct manipulation of neural activity. If neuroscientists electrically stimulate certain brain regions, we can produce hallucinations that are specific to the kinds of experience each particular area produces: if we stimulate areas involved in vision, even a blind person will hallucinate a flash of light; if we stimulate areas involved in face perception, it will distort how you perceive a face; if we stimulate areas important for hearing, you will hear phantom sounds.
These findings raise a crucial question: What room is there for a soul if your perception, your memories, and even your personality are determined by your brain?
In trying to negate this brain-based view of consciousness, it is tempting appeal to the prevalence of near death experiences. The thinking might go like this: when we find ourselves at the brink of death, we experience sensations like a bright light at the end of a tunnel, a sense of having died, feeling that we are floating away from our bodies, euphoria, or meeting deceased loved ones. Such experiences are surprisingly common (though not universal) among the dying. Incredibly, they even seem to persist after the heart has stopped beating. How is this possible if experience depends on the functioning brain?
As it turns out, near death experiences are not the scientific mystery they are often made out to be. Research has shown that there is in fact a brief burst of complex brain activity just after the heart has stopped beating. In fact, brain activity might not flatline until half a minute after cardiac arrest.
The presence of complex brain activity following cardiac arrest tells us that after death, the brain still works long enough to create new experiences (as hallucinations) and to consolidate those experiences into memories. Should you be resuscitated, you will remember those experiences.
Perhaps then we might appeal to the particular character of near death experiences, such as seeing a light at the end of a tunnel, feelings of euphoria, being aware that you are dead, or meeting deceased loved ones, which are all common in near death experience reports. These experiences all seem otherworldly, but can in fact be explained by standard neuroscience.
For example, the sense of being dead is the primary symptom of a brain disorder called Cotard syndrome, in which patients remember having died and believe they are in heaven. Cotard syndrome is caused by changes to parts of the brain called the parietal cortex and the prefrontal cortex, and usually follows trauma or severe illness.
Out-of-body experiences can also be caused by changes in the brain: stimulating a part of the brain called the temporoparietal junction, which processes information about your body’s relationship to your external environment, can cause patients to report seeing themselves lying in bed (an “out-of-body” experience).
The sense of moving through a dark tunnel toward a light can also be induced naturally. In fact, “tunnel vision” it is actually the symptom of a wide variety of medical conditions.
What about seeing deceased loved ones? This sort of hallucination can be caused by a variety of drugs or brain disorders, including Alzheimer’s, Parkinson’s, and Charles-Bonnet syndrome, which afflicts otherwise psychologically healthy individuals. The sense of bliss reported during some near death experiences can also be induced by a variety of psychoactive drugs, brain disorders, or even relatively mundane activities.
It’s not yet known whether the brain processes underlying such experiences in the living brain also occur during the brief surge of brain activity after death. But the fact that such processes and their corresponding experiences can happen in living, conscious brains demystifies the particular character of near death experiences: every common feature of the near death experience has a well-understood neural correlate. We need not invoke a soul to explain them.
What then of reincarnation? There exist thousands of reports of children remembering past lives, some of the most famous of which were collected by the late psychiatrist Ian Stevenson. Stevenson convinced many of his readers – and even some scientists – that reincarnation is real. It should be admitted that some of Stevenson’s reports truly are incredible, if they are true. They include cases in which children remember specific details about previous lives, which they (supposedly) couldn’t have had access to. How could this be possible unless their memories from a previous life were carried into their new bodies via a soul?
The problems with Stevenson’s research are manifold and damning: almost all the cases he reports come from cultures where belief in reincarnation is universal; nearly every child interviewed was acquainted with the family and/or friends of the deceased individual they claimed to have reincarnated from; the children were asked questions that prompted or rewarded answers that bolstered Stevenson’s claims; and one of Stevenson’s translators believed in reincarnation with absolute certainty while the other was himself a past-life regressionist. Picture yourself interviewing imaginative children under these conditions, and see if you’re impressed by such reports.
You might still maintain that the soul is somehow tied to – and yet is separate from – the brain. But if we believe that the soul is some sort of “spirit energy” that interacts with the brain, then we are faced with a number of insurmountable problems. As physicist Sean Carrol puts it: “What form does that spirit energy take, and how does it interact with ordinary atoms? Not only is new physics required, but dramatically new physics. Within QFT [quantum field theory], there can’t be a new collection of ‘spirit particles’ and ‘spirit forces’ that interact with our regular atoms.” In other words, the physical world is causally closed. Physical effects (like brain activity) only have physical causes, and those physical causes are quite well understood. There is simply no reason to invoke spirit energy in explaining the workings of the brain.
So we have established that consciousness depends on the brain, that near death experiences are explainable by neuroscience, that supposed memories of past lives are highly suspect, and that the idea of a soul does not fit into the Standard Model of Physics, which is the most breathtakingly precise description of the world ever devised.
But all of this could be entirely wrong. There could be such a thing as a soul that somehow survives death and is transferred to another realm or into another body. The physics and neuroscience required to accommodate such a reality would be strikingly opposed to everything we know, but we cannot disprove that such is not the case.
Yet neither can we disprove that the workings of the universe aren’t actually the clever craftsmanship of machine elves. We go, as a rule, with the simpler explanation. And as concerns the nature of consciousness, the far simpler explanation – and the one that is consistent with everything we know about physics and neuroscience – is that the soul, as traditionally understood, does not exist, and that consciousness is created by and dies with the brain.
Where do we go from here? Does letting go of an immortal soul mean letting go of morality? As I have argued before, that is certainly not the case. We have every reason to be moral and every reason to love one another in a world made up of of soulless atoms.
But there is the quintessentially human fear of nothingness – that anxiety, familiar to all of us, at the thought of not being. To this, at least here, I have little to say, except that this fear is perhaps misplaced. “Death does not concern us,” wrote the philosopher Epicurus, “because as long as we exist, death is not here. And when it does come, we no longer exist.”
Our time in the sun is limited. We should spend that precious time living well: living with love, happiness, and the pursuit of meaning – and not in fear of what happens when the show ends.