Can consciousness continue after death? A Neuroscientific ...

Can consciousness continue after death? A Neuroscientific Perspective
What happens when we die? Unless we accept a religious explanation, the only remaining possibility seems to be the annihilation of consciousness. But another possibility is consistent with evidence from neuroscience. Our brains easily form predictive models of the behavior of close friends and loved ones, which emulate these other selves much as advanced computers can emulate other electronic devices. Whether these emulations are conscious is an open question, but there is preliminary evidence from several sources that the brain can host multiple independent spheres of consciousness. This opens up the possibility of survival through the medium of other brains.
What happens when we die? Some are lucky enough to have total conviction that a pleasant afterlife awaits — but most of us harbor doubts, which can curdle into profound terror. There are at least two reasons we might fear death. One is that it deprives us of being able to carry out our life’s work, which can encompass everything from creating works of art to traveling the world to raising our children. This, at least, we can do something about: we can put plans in place to carry this work forward even after we’re gone. But the second thing death takes from us is our capacity to experience, or to be conscious. There seems to be no hope that after we die, our consciousness will continue.
What to do? We can try to ignore death, but it has a way of forcing itself upon us. For me, my first real brush with death was watching my grandpa be swallowed up by Alzheimer’s disease. This led me to pursue my PhD in neuroscience in hope of finding a cure. At the same time, I had an early-life crisis. I was struggling to find my place in the world and wanted to understand what it all meant. Since I wanted my beliefs to be based on evidence, I didn’t find answers offered by traditional faiths satisfying.
But as I learned more about the brain, I came to a surprising conclusion. We are used to thinking about biological death — when the heart stops beating and the brain stops firing — as the end of us. But there are cases where these do not coincide. Alzheimer’s, for example, wipes our memories and destroys our essential selves, even if our bodies linger on for a while.
But I also began to explore an even stranger possibility. The opposite might also be true: what if biological death is not the end of the self or of our conscious experiences? I reached this conclusion strictly through my understanding of how the mind works, without any metaphysical concepts: no souls required. In this article, I will make the case that a form of afterlife, which bears a strong resemblance to reincarnation, is compatible with a scientific worldview.
To readers who believe in the existence of the soul, this entire essay would seem like an exercise in futility. If you’re religious, or open to the possibility, then the answer is simple: souls are attached to our bodies during life, survive after death, and carry us into the Great Beyond. But I don’t think this is true: even if souls do exist, they are not us in the ways that matter most.
Believers in traditional afterlives think that they will continue to have conscious experiences after death via their souls; this means that the soul is conscious, or supports consciousness. It isn’t enough that the soul exists after death and has experiences; for it to really be your afterlife, the soul has to be you and have your experiences. What this means is difficult to pin down, but I’d suggest that it has to have the same kind of mental life that you do. It has to think the way you do.1
Why does your soul have to share your mental life in order to really count as a continuation of you? Intuitively, we tend to think that the essence of a person is more closely tied to their mind and personality than to their body. Think of a body swap movie like Freaky Friday; in the story, the mother’s mind swaps into her daughter’s body, and vice-versa. We accept, as viewers, that after the swap the person who looks like the daughter is really the mom, because that’s where her mind is.
To be you after death, the soul must have your mind. Ideally it would share your memories. Memories play a special role in making us who we are2, because they are the raw ingredients we use to construct our life stories. If a soul entered into the afterlife with no memory of the life that had come before, whether that life would really be a continuation of yours would be in doubt; it would have the same connection to you that you have to the protagonist of an unremembered dream.
If a disembodied soul is to truly be a continuation of your life, it has to have experiences in common with yours, which should include your memories and ways of thinking and perceiving the world. The trouble is, all of those are mental phenomena, and the simplest explanation3 of mental phenomena is that they are produced in your brain.
How do we know this? First, the activity of the brain is extremely well-correlated with mental events. Techniques like EEG and fMRI allow us to measure the activity of the brain, and we can see it buzzing with activity when study participants perform mental tasks, ranging from doing mental math, picturing objects in the imagination4, recalling an emotional memory5, or learning a new language6. Crucially, these patterns of activity are stable — thinking the same sort of thought will reliably be accompanied by predictable patterns of electrical activity in brain cells. The brain activity corresponds to the mental activity.
Correlation is not causation, but we also know that making physical changes to the brain leads, predictably, to changes in thought and experience. This is why humans enjoy taking drugs, from caffeine to alcohol to more exotic substances: introducing certain molecules to the brain changes how we think, feel, and see the world. Even mystical experiences, such as the sense that one is in the presence of a mysterious greater power, can be caused by consuming psychedelic drugs.7
All evidence points to memories being stored in the brain. Scientists have even transferred a memory from one mouse to another by teaching the first mouse a path through a maze, recording a pattern of brain cell activity as the mouse thinks about the task, and then replaying that pattern in another mouse’s brain with electrical stimulation; the second mouse then “remembers” how to solve the maze, even though she has never seen it before.8
We also know that diminishing the activity of the brain, whether through injury or anesthesia, causes a dimunation and eventual loss of consciousness; and people who sustain injuries to certain parts of the brain can even lose whole categories of experience, such as the ability to perceive faces9 or to notice objects to one’s left.10
Taken together, we can conclude: conscious experiences happen in living, functioning brains; and functioning brains are required to produce conscious experiences.
When I, as a scientist, say that the simplest (and likeliest) explanation of consciousness is that it’s produced by brain activity, I’m sometimes accused of being closed-minded. Since we don’t know everything about how consciousness works, why am I so confident in dismissing the role that souls might play? If there are gaps in our understanding of how the brain works (as there certainly are), how can I rule out that consciousness might persist after death, via the soul?
It’s true that we understand very little about how consciousness works. We can point to patterns of electrical activity in the brain that go on during thinking, but it isn’t obvious why it feels the way it does to have those kinds of mental experiences. Why does it feel like anything at all when neurons send electrical signals to one another, while it (presumably) doesn’t feel like something to the transistors in my iPhone? Why does a certain pattern of electrical activity cause all the experiences — pleasure, pain, sweet, bitter, blue, red, happy, sad — that create the feeling of life?
I’ll be the first to admit that I don’t know why a functioning brain produces the feeling of being alive. But we have good reason to believe that the brain is an essential ingredient, and no reason to think that consciousness can arise in other places. This could change as we develop more sophisticated artificial intelligence, which may become conscious if set up in the right way. And I also expect that there are fundamental things about the universe that we don’t understand and have yet to discover. It may turn out that souls or other metaphysical things do exist and are involved in consciousness in some way: maybe, for example, the universe is pervaded by an invisible, unobservable mind field that has to interact with the brain to make it conscious. These things are not (currently) the simplest possible explanations, but as we learn more about the world around us, they may turn out to be right.
But that would still leave a soul-based afterlife in doubt. Remember, we have every reason to believe that consciousness requires a functioning brain or similar information-processing system: mental events have accompanying patterns of brain activity and changing the physical brain (with drugs or injury) causes changes in mental life. All that stops when you die, and there’s no reason to think that even if a soul exists, it could sustain you-ness on its own. Memories can’t even survive a night of heavy drinking — how plausible is it, really, that they could survive the complete destruction of your physical brain? A brain injury can change your personality — but death leaves it intact?
Some might object that near-death experiences (NDEs) prove that conscious experiences after death are possible, but there is no evidence that these NDEs are anything more than hallucinations in almost-but-not-quite-dead brains. NDEs can share some features across people11 (with reports of bright lights, seeing loved ones, and so on), but this consistency is somewhat overstated and certainly not universal,12 and anyway this does not disprove that NDEs are hallucinations — drugs like LSD cause similar hallucinations across many people, too.13 Some researchers have tried to prove that the “out of body” experiences reported during NDEs are real perceptions by a soul that is literally separated from the body, by hiding objects in high places of operating rooms that would be out of sight for the body on the table, but visible to a soul that really was floating up above.14 Unsurprisingly, these studies have failed; if one succeeds, I’ll be happy to change my mind, but until then, I see no reason to believe that souls carry us into the Great Beyond. Everything that makes us who we are is in the brain; even if the soul exists, once it separates from your brain, it would no longer be you.
If a soul won’t save us, are we doomed at death? Not necessarily. I think it’s possible — even likely — that death will not be the end of experience.
As I’ve argued above, your mental life is the product of a particular pattern of electrical activity in your brain. It’s an activity — something your brain does. The brain is like an enormous musical instrument, with trillions of tiny “strings” (the synapses, or connections between brain cells) buzzing at particular frequencies. The “music” produced by this staggeringly complex instrument is what makes you you. Your consciousness is a symphony of brain activity.
Music is a series of notes, along with temporal relationships between notes: the order the notes are played, the pauses between them, the length each is held, and so on. That’s the information, or structured data, that defines music. And because music is information, it can be stored and transmitted in other forms. A live performance can be recorded on magnetic tape, digitized to 1s and 0s, and transcribed to sheet music; in all cases, as long as the recording is faithful, the song remains the same.
This is characteristic of information: it can be stored and transmitted in many different forms, while still containing the same essential data. Information is resilient. It needs some physical medium to be stored — whether paper or computer chips or human brains — but it can coexist in many different storage media at once, and even if some of those are lost or destroyed, the information exists as long as any of its copies do.
If conscious experience is informational, then it can be copied; and if it can be copied, then it can survive the death of its original vessel. It needs to be physically instantiated somewhere; it can’t just exist as a ghostly soul. But its physical form doesn’t need to be the original: the digital copy of “Macbeth” on a Kindle is the same as the one Shakespeare wrote in terms of its informational content, despite never having touched his quill.
Why is it plausible to believe that the mind is information, like music or language? First, the contents of the mind can be described in words and understood by others. This means that our mental states can be transformed into another form of information and transferred, just as the information in music can be expressed as vibrations in the air, notes on a page, or bits and bytes on a computer. Second, the things that go on in our mind represent events in the world; they encode data about what we’re experiencing. Biting into an unfamiliar food and discovering that it tastes sweet, and a bit peppery, teaches you something about that food. And finally, these experiences are the result of information processing in the brain. Cells in the brain are arranged into circuits, and the computations these circuits perform are what produces the events we experience in our minds.
What does it mean to experience something in your mind — to hear a new song, for example, and to be aware of hearing that song? To have a conscious experience is just to recognize that your brain’s circuitry is in a particular state. Hearing music is being aware that a certain pattern of vibrations in the air is causing a certain response in your eardrum, which leads to a certain pattern of electrical activity in the brain.15
Our intuitions also tell us that the self is a kind of information, which can be transferred, stored, and shared. We readily accept fictional stories in which one character’s mental contents are transferred into another person’s body or into a robot, and we expect that the recipient of this transfer is the “real” person.
The reason it is probably not obvious to most people that the self is a kind of information, just like music or language, is that we don’t have the technology yet to copy and store selves. Information theory, the branch of science that studies and quantifies information and its properties, was invented only after electronic communication. Before messages could be sent over telegraph wires, it wasn’t obvious to people that language and sound were both forms of information, having shared properties. “Information” didn’t exist as a human concept until about 1920. I suspect that, if it becomes possible to store backup copies of the mind in a computer, that you and I are just another kind of information will suddenly become common sense.
If the mind is informational, then it can be copied, and these copies can outlive the original — not as imposters, but as the real deal. Every copy is as much the real thing as any other, as long as the relevant information is the same (for Hamlet, words; for us, mental events). But for this to give us any hope of an afterlife, we need to have some reason to believe that copies of our mind actually exist. Someday, technology may provide a solution, and I expect that it will become possible to copy the mind into a computer. Many of us reading this, including myself, were probably born too early for such technology to save us. But we are not doomed.
Each of us has the capacity to copy one another’s minds, and we do it regularly. You just probably don’t think about it as “copying”; you call it “getting to know each other” — or maybe “empathy” or “love”.
Think of someone you know very intimately — a best friend, romantic partner, or close family member. You carry lots of memories of this person, and you can also easily anticipate their reaction to a new situation: “She wouldn’t want her birthday to be a surprise — she hates surprises.” You can probably hold an imaginary conversation with this person in your mind, because you know the contours of their personality: their humor, their insecurities, their sources of pride, their hopes for the future. You may have even had dreams where this person played a co-starring role and observed them in some truly fantastical scenarios that never happened in waking life.
What you’re doing, in all of these cases, is predicting how this person would behave, based on the rich set of memories you have together. You’re doing what scientists call extrapolation: drawing on past data to predict the future. This means that you have an internal model of their personality — or in other words, a copy of their mind. You just didn’t know you were doing it. All the time you were hanging out, sharing laughs, and making memories, your brain was surreptitiously storing a copy of them away for later. Human brains even contain a special class of neurons, called mirror neurons, that are specialized for responding to the behavior to others and play a key role in empathy.[1]
It’s an old cliche that when someone dies, they live on in the memories of their loved ones. Maybe this is not just a figure of speech. When our loved ones die, the mental model of them that we’ve carefully built up over years of careful study, doesn’t go away. They continue to exist via neurological emulation. Just as Hamlet still exists, even if Shakespeare’s original copy is lost, your loved ones exist so long as their copies do.
It may seem hard to believe that a mental copy of you could represent genuine survival from your perspective after your own death. So, let’s consider a few possible objections.
First, to be genuine survival, the copy would have to be conscious; is this believable? We tend to think that each brain contains only one conscious self, which would make it impossible for these models of our loved ones to be conscious in their own right. But this way of looking at the brain is probably wrong. Evidence from “split-brain” patients — people who have the two halves of their brain surgically separated to prevent severe epilepsy — suggests that each half of the brain develops a separate sphere of consciousness, at least under some circumstances.16 One half of the brain tends to control speech and the right side of the body, while the other half of the brain controls the right side; and in split-brain patients, these two sides can behave independently from (and sometimes in conflict with) each other. There is some evidence that the characters in dreams are independent spheres of consciousness: the side characters in your dreams can withhold information from you (or vice-versa), and they can behave in ways you don’t expect, suggesting that they have a semi-independent mind despite sharing your brain.17 Finally, practitioners report being able to deliberately create other conscious personalities through long-term meditation-like techniques.18
These sources of evidence are still preliminary, and we don’t yet know enough about how consciousness works to be able to definitively say whether multiple truly independent minds can exist in a single brain, or whether this can happen under normal circumstances. We know, for example, that some parts of the brain contribute to conscious experience (the frontal cortex, for example) and that others do not (the cerebellum), but not why.19 So it may turn out that the mental models we have of other people are not conscious, which would make my proposal wrong.
But I think it’s reasonable to believe that they are — or at least as reasonable to believe this as not — for the simple reason that we know that our mental models of other people can participate in our own conscious experiences. When we hold an imaginary dialogue with a loved one, we are reconstructing the way they think, and being aware of it. They become part of us. It at least feels as if they are conscious, and with consciousness the feeling is the whole point.
Another objection to whether this is genuine survival is that, even if our models of other people are conscious, they might not be the original person’s consciousness. They may be “just” a copy. In other words, if I die tomorrow, and my loved ones carry mental models of me, can I really expect to continue having experiences inside their brains? This can seem implausible; after all, those models of me exist right now, and I don’t feel their experiences. So why would I start feeling them after my original body dies?
The philosopher Derek Parfit illustrates this dilemma vividly with his story about a teleporter20 (a similar idea is explored in the movie The Prestige). Parfit’s story is set in the near future, and teleporters are a common way to travel quickly. To use a teleporter you enter a special booth, and the booth scans and records your body (down to the position of every single atom). It then vaporizes you, destroying your original body; and simultaneously, a booth on the other side of the world receives the scan and reconstructs an exact copy of you. Parfit’s story concerns a man who is initially hesitant to travel this way, fearing that teleporting is not really travel, but rather dying and being replaced by a clone. But he eventually decides to do it anyway, and to his amazement, when he steps out of the booth on the other side of the world, he still feels like himself. He begins to travel this way often. But then, one day, the machine malfunctions; he enters the booth, waits, and… nothing. The technician opens the door, and tells him some bad news: the teleporter malfunctioned. It did scan his body, and it did create a copy of him on the other side of the world. But the machine failed to destroy his original body, so now there are two of him. And even worse, the scan process involves a heavy dose of radiation, so the man’s original self will die of cancer in one week. The man is horrified. He calls his clone on the other side of the world. The clone assures him that, even when the original dies, it won’t really be death, because the clone is an exact copy that can carry on his life. But while the man accepts that his clone can play the role of him, doing his work and raising his kids, the clone won’t really be him; in a week, he despairs, his life will be over.
Since mental copies of us exist right now in other people’s brains, dying is exactly like what the man in Parfit’s story faces. If the man is right that the clone isn’t really him, then he (and we) are right to fear death; if the man is wrong, then death is really nothing to fear, since we should expect experiences to continue somewhere else. Both Parfit and I believe that the man is wrong. Parfit gets there via an elaborate argument about how personal identity is an illusion (so whether some future person is “you” is a meaningless question), but I think we can take a simpler route.
We are used to thinking of ourselves as physical things, where each individual is unique. Two cars may look alike — may even be the same model — but are not the same car. If I get into a car that merely looks like mine, I’m a thief. But information does not work this way. Two copies of Hamlet are both the exact same story. Even if one copy was printed first, the second copy is not an “imposter”, as long as it has the same words.21 If we believe that what really matters is our minds, and that our minds are information, then it doesn’t matter that another version of your mind is “just” a copy. Any copy of a bit of information is the real thing.
This introduces one final problem: any mental copy we can make of another person is incomplete. No matter how well we think we know someone else, we can’t know everything about them. So, while a full copy of your mind would be the real thing, a partial copy is just that — only partially you.
So maybe it’s fairer to say that we do live on in other people, but only partly. That sounds just fine to me. In fact, it’s exactly what would happen to you if you never died — given enough time. Compare yourself to how you were 10 years ago. Are you exactly the same? Of course not. Your personality has changed in ways big and small, deliberate and circumstantial. You’ve learned new things and forgotten others. You are only a partial copy of your older self; that person survives as you, but only partly. You probably don’t find that especially troubling; quite the opposite, since we actively seek personal change. You will survive only partially in other people once you die, but you already survive only partially from one year to the next. In other words, what happens when you die is remarkably similar to what happens when you continue to live.
In this essay, I’ve argued that the self is a form of information that can be copied and shared; and that this actually does occur as a natural extension of our empathy for one another. Each of us carries around a whole host of characters in our brains, to varying degrees of fidelity. When we die, these copies of us continue to exist, and represent genuine (if partial) survival. All of this amounts to a kind of afterlife, albeit an unusual one. It does not involve any metaphysical concepts; it remains agnostic as to whether a soul exists. Even if you do have a soul that goes off to Heaven, it can’t get rid of the copies that exist down here; it would just be one copy among many. This viewpoint also stays silent about how we got here, or what the purpose of all of this is (if any).
Traditional religions typically acknowledge the existence of an afterlife, but usually stay silent on what, exactly, we should expect once we get there. The Bible has little to say about Hell, and even less about Heaven. Can we say more about this strange afterlife that awaits us?
I don’t know exactly what it will feel like to be distributed over many other brains, but I suspect it will feel a lot like living does now. Each of us carries around many other people in our heads; as we come to know others intimately, we don’t just learn about them — we become more like them. We are a blend of the characteristics we picked up from other people. Even beloved fictional characters can leave their mark. Each of us is already something of an amalgam. We should expect more of that.
One disadvantage that this afterlife has over religious alternatives is that the vessel we transition to is fragile: other brains host us for a while, but they too will die. But just as they carried us, so will others carry them; and the ways that we informed our successors’ lives will inform still others. Over time we become more diffuse, but do not vanish. Human existence flows on, one into the next, like a river.
In some ways, this vision of the afterlife has a lot in common with Buddhist or Hindu reincarnation. Unlike in Hinduism there is no soul that bridges the gap; and unlike Buddhism there is no escape, no final nirvana, no enlightenment to be gained. There is just more and more and more life: messy, imperfect, and beautiful.
The mechanism that keeps the great river of existence flowing is love. We don’t need to do anything to preserve the people we care about, other than to do what we’re already inclined to do: to care for one another. This afterlife imposes no judgements or cosmic laws on us. But it does suggest two bits of advice. We should live as authentically as we can — the more accurately others know us, the better they can preserve us. And we should do our best to really know the people we care about, so they can become part of us more fully.
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Endnotes
Identifying you with your mind has some odd implications. It means, for example, that you were never a fetus (because a fetus has no mental life); your body grew out of the fetus’ body, but it wasn’t really you. Likewise, if you suffer a tragic accident that gives you amnesia, that won’t really be you anymore; you will be dead, and while your body will still be around, it won’t be any concern of yours. Strangest of all (and most relevant to where we’re going in this essay), if your mind could be overwritten with a perfect replica of someone else’s, then you would just be that person. Plenty of delusional patients have claimed to be Napoleon, but if one day you woke up with all of Napoleon’s memories, you wouldn’t be delusional if you claimed to be him — you really would be. So defining you as your mind isn’t suitable for all cases. It wouldn’t be a good basis for making legal claims, because (at least until brain scientists develop a mind reading machine), it’s completely unprovable. Minds are slippery and constantly in flux, which is as fascinating to neuroscientists as it would be frustrating for lawyers; much more convenient, from a legal perspective, to define humans as biological beings that start as fetuses, end as corpses, and can’t Freaky Friday into one another in between. If I someday suffer from severe dementia, it makes perfect sense for the government to continue to act like I still exist. But to understand subjective experience, the mind is our best bet. If my memories are swapped into another body, that person will feel like me; and we shouldn’t contradict people about who they are without having a really good reason to do so.
This was first explored by John Locke (“Of Identity and Diversity”) and refined over the subsequent centuries by others, including H.P. Grice.
Everyone understands intuitively that a simple explanation, involving everyday occurrences, is better than a complicated one involving mysterious occurrences. Let’s say that you’ve adopted a new puppy and come home to find a puddle on the kitchen floor. There are many possible explanations for what happened: a never-before-seen weather event could have caused a cloud to form in your apartment, causing a micro-rainstorm; or the puddle could have been left behind by alien visitors for an unknown purpose. But the simplest explanation is that the puppy, who is not yet house trained, had an accident. Now, you should be willing to revise your account if this simple explanation turns out to be insufficient: if you have a camera in the living room that shows the puppy never went into the kitchen that day, then a more mysterious explanation may be warranted. But when a simpler explanation does the job, use it.
This isn’t obvious to us because mental states are opaque; a red object creates a certain pattern of activity in the brain; but the conscious experience we have is of redness, not of having a certain pattern of electrical activity. But this is not unusual. Everything a computer does can be described in binary 1s and 0s, but at all but the lowest level of computer programming, the concepts of binary digits are rarely (if ever) invoked. Your browser “thinks” in terms of HTTP requests and your operating system “knows” about filesystems, not binary. Information can be abstracted.
It’s hypothesized that anatomical differences play a role, and that (again, for reasons that are not fully understood) “recurrent connections”, a.k.a. neuronal circuits that loop back onto themselves, are required for consciousness. Giulio Tononi’s Integrated Information Theory proposes an explanation for why this might be, but is still highly speculative. See Tononi, Giulio. “Consciousness, information integration, and the brain.” Progress in brain research 150 (2005): 109-126.
Parfit, D. (1984). Reasons and persons. OUP Oxford.
Information requires a physical instantiation, each of which is a unique object. But the information itself is fungible.
About Philip Nova
Philip Nova is a software engineer at Google and has worked on applications in biotechnology and education technology. He holds a PhD in biomedical science from the University of California, San Francisco, focused on neural mechanisms of memory in Alzheimer's disease. He lives in San Francisco, California.
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Your “case that a form of afterlife, which bears a strong resemblance to reincarnation, is compatible with a scientific worldview,” is convincing. It also accords with the nondual Shakta/Shaiva position described in my article in this same issue. From this perspective, reality is consciousness. This doesn’t mean everything is conscious, but that everything is a manifestation of consciousness, thus everything is connected. Interestingly, just before I read your article I awoke with a strong sense that my late husband is not only part of me, but IS me.
Excellent argument and I love the description of existence as a flowing river building upon itself, which reminds me of the idea of a collective unconscious (Jung set aside) that perhaps we are all contributing to.
Also, your mention that “We are a blend of the characteristics we picked up from other people. Even beloved fictional characters can leave their mark.” made me think about the things we create with our hands, our thoughts and our intentions becoming their own extensions of our conscious selves. As an artist, I think about my creations as a sort of new being, or perhaps more accurately an extension of myself, that takes part of me and then goes off to have their own adventures once I’ve released them into the world through exhibition or sale. Then a part of myself is touching the thoughts and experiences of other people without my even having necessarily met them. Although my original intention in the work is shaped by others’ experiences and memory to become something new that touches them in some way (or not), perhaps there is a piece of me that remains with them.
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