I was having dinner with two friends the other day, when the dinner-table banter took an existential turn. One of them, a philosophy major, had brought up a thought-provoking paradox called ‘The Ship Of Theseus’.
According to legend, when Theseus returned to Athens after slaying the Minotaur, his ship was preserved as a memorial. The Athenians had vowed that if Apollo granted them victory, they would sail to the island of Delos each year in the triumphant vessel to worship him. So Theseus’s ship had to be kept in a seaworthy state. If a plank or oar wore out, it was replaced with an exact replica. Centuries passed and the ship looked the same, but the cumulative repairs were so extensive that it no longer contained any original parts, leading philosophers to debate if it was still the same ship.
In another version, the discarded pieces were collected by a patient conservationist over the years, and meticulously reconstructed in a museum. So now we end up with two ‘Ships of Theseus’, but which is the real one?
There are many possible ways of looking at the problem. A conservationist would probably say that the one sitting in the museum is the real ‘Ship of Theseus’, because its planks were the very ones that Theseus stood on when he sailed back to Athens. The artefact is of interest because of its connection to a historical event. In this sense, the one floating in the dock is just a replica, but we were confused because the change happened gradually. Imagine if the Ship of Theseus were destroyed in a dramatic explosion, and the Athenians built a new one that looks exactly the same. Nobody would mistake this second ship for the original one.
Furthermore, the fact that the museum ship was reconstructed from broken pieces is no objection. After all, conservationists often piece together fragments of artefacts (e.g. antique vases) from archaeological excavation sites. These priceless pieces are ‘one-of-a-kind’ because they have been touched by history, even the fact that they are incomplete or damaged does not detract from that value. Holding them in their hands, historians feel a visceral connection with the past. Conservationists are careful not to overdo a restoration. At a Sotheby’s auction, a derelict Ship of Theseus could be worth millions in its run-down state; but be worthless when fully restored to its original splendour, because then its authentic status would be irreparably compromised. So too for Renaissance paintings and 1,000 year old porcelain.
But paintings and pottery are dead, static objects that stay more or less the same for thousands of years. Unlike fragile artworks kept and displayed in glass boxes, Theseus’s ship endured yearly pilgrimages to Delos. It was also made of perishable wood constantly soaked in corrosive sea water, unlike ceramics inert as stone. The rate of change was higher. So ceramic vessels are not a fitting analogy for things with an even more violent rate of change than wooden ones, i.e. living things like the human body.
In a physical sense, we are literally not the same person we were 10 years ago. We are like a flesh and blood Ship of Theseus. For instance, red blood cells last 120 days, and the cells lining our intestines last only 5 days. Our liver has a turnover rate of 300 to 500 days, while our entire skeleton is fully replaced every 10 years. At the level of individual cells, molecules are also constantly being replaced. In 1953, scientists found that 98% of the atoms in our body are replaced on a yearly basis (here). This is what food is for, e.g. we take amino acid molecules from meat to repair our muscles and grow new cells, to fend off the wear and tear of daily functioning.
However, the question is not really how we can remain the same person when our bodies today contain no original cells or even atoms from 10 years ago. For example, someone who receives a heart transplant remains the same person. We can even imagine someone undergoing multiple organ transplants over many years (like a real-life Tin Man from ‘The Wizard of Oz’) until his intestines, lungs, face and limbs are all replaced with those of organ donors; yet he would still be the same person. The organ we are really interested in is the brain, the supposed seat of our identity and consciousness.
It turns out that unlike other cells in the body, neuron cells can live for up to 120 years and are not subject to replacement. Neurons make up the cerebral cortex, a thin 4 millimetre layer on the brain’s surface where thought processes are thought to occur. While this might seem to suggest that the brain is exempt from the Theseus Paradox, the cerebral cortex accounts for only 10% of the brain, the other 90% consists of non-neuronal glia cells (now thought to play a more integral part in thinking, and perhaps consciousness, than previously suspected) and other parts like the hippocampus (which plays a crucial role in memory). These cells are subject to the same flux and replacement like other tissues in the body.
Yet it may not really matter. Even if brain cells had a high turnover rate, you can still remain you. It could very well be that what makes you ‘you’ are not the exact molecules or neuron cells; but the structural relationships between them. In other words, it is the ‘software’ that is key rather than the exact ‘hardware’. The individual cells or molecules can be replaced without threatening the survival of your “selfness”. As long as the turnover of your brain cells is managed in an orderly manner, your consciousness continues to exist.
However, even if our neurons stayed with us from birth to death; you are still not the same person you were 10 years ago. As we experience different things, our ‘software’ changes (presumably, there would need to be corresponding physical changes in the neurons to store the new information, even if they are still the same neurons). We are different not only in a physical sense, but more fundamentally in a psychological sense. For example, is an 60 year old man the same person he was at 6 years old? On the one hand, common sense insists they are a single person. Yet on the other hand, there are also two radically distinct persons, e.g. as a boy, he was weak and meek; but at 60, he’s become a hardened war veteran. What exactly is it that remains constant throughout those 54 years which allows us to say that the timid boy is the same person as the war hero?
In his 1984 book, ‘Reasons and Persons’, the philosopher Derek Parfit argues that they are the same because of “psychological continuity”, which is a revised version of John Locke’s idea that a person continues to exist because of direct memory connections, or “psychological connectedness”. That is, if the 60 year old man can remember the experiences of the 6 year old boy, then they are the same person.
Parfit’s version is less strict, there can be continuity of memory even when there are no direct memory connections. For example, if at 20 the man remembers what happened when he was 6, and at 30 he forgets what happened at 6 but still remembers what happened at 20, he is the same person. “Psychological continuity” is preserved if there are such overlapping chains of connectedness. It also applies to other psychological features like desires, beliefs and intentions. If enough of a person’s psychological makeup are linked in this way over time, he is the same person. Parfit calls this, “Relation R”. Unlike Locke’s rigid “psychological connectedness”, Parfit’s account allows for identity in the face of change. Or so it seems.
Individuality is a foundational concept in Western thought. I am who I am because of how I am unique and apart from other people. I am a category of one. There is only one ‘me’ in all of history and the world. So one answer to what makes us who we are might be our psychological uniqueness; i.e. the entire history of experiences that shaped our character, the sum of our memories, our personality, our habits, our quirks, our evolutionary instincts, our choices and preferences, and so on. In other words, our identity. This is what gets preserved in Parfit’s ‘Relation R’. Yet by equating the ‘self’ with ‘identity’, we seem to have muddled up the issue of consciousness.
In ‘Hammerhead: Shark Frenzy’, a pulpy 2005 B-grade horror movie, a scientist tries to save his cancer-stricken son by ‘adding shark stem cells to his DNA’, but ends up turning him into a mindless shark/human monster that proceeds to kill off the people trapped on an island. At one point, the son’s girlfriend wants the creature spared, in hopes of finding a way of reversing the transformation; but the hero argues that her boyfriend ‘died’ when he turned into that thing. It is not her boyfriend any more, and there’s no humanity left in that creature’s mind but the impulses of an animal.
fig. 5: Horror stories about ex-boyfriends — Sharkman.
It’s like how we say a grandfather in the late stages of Alzheimer’s is no longer who he used to be. He may not remember any of his children, or his wife of 60 years, or has forgotten how to play the piano etc. That is, he has lost all aspects of his identity. He may seem to be the same person, alive and well, but his mind is long gone. There is nothing left inside any more, like a computer hard-drive wiped clean of its data. We use expressions like, “he is but a shadow of his former self”. Their ‘soul’ has already gone, leaving behind a mere shell. In fact, some Westerners say they would chose assisted suicide if it came to this, because they believe it is a state no different from death.
Yet there obviously must still be some consciousness lingering in that body (or more precisely, the brain). If we pricked a catheter into the patient’s urinary tract, he would still wince in pain, or even fear. There are cases of normally honourable elders, who in advanced stages of the disease develop a prurient, uncharacteristic fascination in the butts of teenage girls; morphing into serial molesters. So who is it feeling this pain (or lust), if it isn’t the same ‘person’ before the onset of mental deterioration? So it seems that even after losing all aspects of the identity that defines us, that makes us who we are, we will still continue to exist. Consciousness has nothing to do with identity. The ‘self’ is something else entirely, and seems to survive even the loss of Parfit’s “psychological continuity”.
For want of a better term, let’s call this nebulous secret ingredient “experiential continuity” for now. It is similar to Parfit’s ‘Relation R’, but is nothing more than the raw conscious experience which arises from our biology. This moment to moment awareness doesn’t require any content. The details of our psychology might not be as essential to our selfhood as Parfit thinks they are, but are merely extraneous Christmas ornaments hanging off of it. A creature would be conscious even if it remembers anything it sees for only a fraction of an instant.
“Experiential continuity” would be consonant with the Buddhist theory of an unbroken “stream of consciousness” linking one lifetime to next. But although it flows on and on, it is different from the idea of a ‘soul’ (which the Buddha rejected as false). Buddhists do not see this continuity as a ‘self’, because it is forever changing from moment to moment and from life to life. It has no substantive identity that can be pinned down. Only that which is eternally unchanging can be considered our true self, i.e. the inherent Buddha-nature which is rediscovered after putting an end to this never-ending cycle of change and rebirth.
The Western conception of personality and identity is also at the root of a common objection to the Buddhist theory of rebirth. For example, some might reason that, “I can’t imagine myself being reborn as a lower life-form like a slug, an ant or a cow. I mean, our brains are obviously more sophisticated than the brain of an ant, so how is all that information in my mind going to get transferred into the tiny brain of an ant? If I lose most of those characteristics that make me who I am, then I am by definition no longer ‘me’, and I will cease to exist. Ergo, rebirth is impossible.” This is a sign of “category blindness”. Cows and humans belong to different categories, therefore it seems ridiculous to think that a human being can become a cow.
Yet in real life, people do suffer from losses of mental capacity. If a genius loses half his brain in an accident and becomes a retard, does he cease to exist? In the late stages of Alzheimer’s, is a patient replaced with another ‘person’ (or consciousness)? Furthermore, it is also entirely possible to imagine scientists inventing some procedure (perhaps involving futuristic genetic/nanotechnology) that can slowly morph the cells in a person’s body into that of a slug. Over the course of say 50 years, the subject remains fully alive, but his body and brain are gradually mutated and shrunken down until all that’s left is a slug. Like how an 6 year old boy is still the same person at 60; our mutant slug is still the same “experientially continuous” consciousness, as the man it started out as.
fig. 6: “The marine slug has a relatively simple nervous system, with about 10,000 large neurons[…] even so, its brain cells communicate in ways identical to human neuron-to-neuron messaging.” (here)
A valid reservation about rebirth might be the fact that there is as yet no scientifically proven mechanism to conserve experiential continuity after the perishing of the brain, but if we accept that ‘experiential continuity’ is more important to the persistence of selfhood than ‘psychological uniqueness’, then the differentness of humans from animals cannot be used to rule out the possibility of rebirth. It may be possible for a ‘stream of consciousness’ to pass from one category to another.
However, it could be that we haven’t moved from one category to another after all. What we are interested in is ‘consciousness’; not ‘cow-ness’, ‘slug-ness’ or ‘human-ness’. Rather than get hung up on what is a “cow’s psychology”, our main concern should be the list of attributes which qualifies something as being conscious, e.g. perhaps it has to be aware of itself. The brains of everything from an oyster to a musician might all fulfil such a definition of ‘consciousness’. Then rebirth starts to look less paradoxical because consciousness is now a more general quality that is universal to different categories of life forms.
We also seem to confuse ‘consciousness’ with ’cognition’ (Descartes’ “I think, therefore I am”), so some people argue that oysters and insects cannot be conscious because their nervous systems are too primitive to support complex thought. Yet unlike ‘cognition’ which differs according to the level of intelligence, consciousness may very well be a phenomenon that tolerates far greater leeway than we imagine, that can be implemented in a wide range of systems with varying levels of sophistication (within some limits, TV sets and vegetables are probably not conscious). A mentally retarded child is neither more nor less “conscious” than a mathematics prodigy, even if their minds are obviously different in other ways. ‘Stupidity’ does not preclude consciousness.
In his 1975 book, ‘Rebirth As Doctrine and Experience’, the Buddhist writer Francis Story offers a similar analogy — “no one would deny, least of all a Buddhist, that the human mind is vastly richer, incalculably wider in scope, and capable of producing a far greater variety of thoughts and activities than that of an animal — this we can assert with safety even though we know so little about the subjective life of an animal that we cannot even be sure whether they experience colour perception in the same way as we do. But it seems that there is simply a difference in the quality and range of the mental activity, while the basic processes and even fundamental motivations are the same. Put in another way, we might say that the difference between the consciousness and responses of an animal and those of a human being is rather like the difference between a child’s toy piano of one diatonic octave and a concert grand. Basically, they both produce sound by percussion”.
The category is the most basic unit of Western thought. Something that possesses certain attributes belongs to a certain category. For instance, the ‘Ship of Theseus’ may be defined as “the floating mass of wood that Theseus sailed to defeat the Minotaur”. The defining attribute is not its likeness or shape (since that can be forged). Therefore, if none of the wood in the present ship was involved in the historical voyage to Crete, the entity is no longer coincident with the category ‘Ship of Theseus’. There is a certain rigidity to categorical reasoning, a clear cut “either/or” quality.
The case of Theseus’s ship is perplexing precisely because it violates this basic logic underpinning Western category-formation, because it is essentially about the contradiction between change and the persistence of identity. Something either belongs to a category, or it doesn’t. How can something jump from one category to another and still be considered the ‘same’ thing?
The Ship of Theseus was basically just a list of physical attributes. Change enough of them, and it becomes something else. It falls under a different category. For example, if you burn the Theseus Ship and grind it into a pile of ashes, it is no longer a “ship” but a “pile of ashes”. There’s nothing controversial about that. But lifeless objects are too simple to be good analogies for selfhood. Ships are not conscious. They are not self-aware, they have no concept of a self. Although people (like ships) are made of physical parts and substances too, something mysterious seems to arise out of the interaction amongst these parts. We may not know which ship was Theseus’s, but we seem to know that we are the same person we were two minutes ago. Or are we? What exactly makes us who we are?
The Buddhist concept of change through ‘rebirth’ is also more radical than the Theseus Paradox. It would be more akin to tearing apart Theseus’s ship and building a wooden house with the parts. In 2005, a British conceptual artist won the Turner Prize for a work which did just that. For his ‘Shedboatshed (Mobile Architecture No 2)’ (2005), Simon Starling found a wooden shed on the banks of the river Rhine in Germany, dismantled it and built a boat with the planks, loaded the left-over pieces onto the boat and navigated it down the river to the Kunstmuseum Basel where he dismantled the boat and reconstructed the shed in a gallery.
fig. 7: Simon Starling’s Shedboatshed, before and after. Is it the same or a new shed?
Although meant as a statement against mass-production, the work poses interesting ontological questions. Did the shed temporarily cease to exist while it was a boat, reappearing again when it was ‘resurrected’ in the gallery? Although both sheds are exactly the same physically, are there actually two different sheds, with the original one forever destroyed the moment it was turned into a boat? Similarly, we can imagine there are such things as werewolves, i.e. people who change into wolves during a full moon. When such a person turns into wolf and back into a human being, is he the same or another person? Or are the ‘human’ and the ‘wolf’ “psychologically continuous”?
Suppose a peasant found Noah’s Ark, and ignorant of its biblical significance, dismantled it make a bathing shed. Is this “Noah’s Shed” still “Noah’s Ark”? Apparently not, because a ‘shed’ is not an ‘ark’. So has the ark ceased to exist? It would be like a person’s brain breaking back down into atoms in the grave, and the atoms are absorbed by an apple tree to form part of an apple. Of course, the apple is not the person even if it were made of the very atoms that made up his brain. The apple is not conscious like the brain; since it isn’t the actual material components of the brain that gives it the property of consciousness, but that they are linked together in a functional manner. Similarly, a shed lacks the functional nature of an ark. A shed is a shed and an ark is an ark, period. So the ark is no more.
But suppose a sharp-eyed historian comes along and suspects the shed might be some important artefact. He buys the entire shed and ships it to his university, where a team of conservationists carefully takes it apart and figures out how the pieces once fitted together. When the jigsaw puzzle is complete, the historian realises the enormity of his find, and announces his coup to the world in a sensational National Geographic documentary. He has found Noah’s Ark.
Yet this flimsy, fragile vessel has missing planks and holes in the hull, and must be kept in a temperature-controlled chamber. It can never float again. So why would most people accept it as the ‘original’ Noah’s Ark? It’s like how in medieval times, splinters of wood were peddled as fragments of the True Cross (i.e. the actual cross on which Jesus was crucified). Even if these pieces were authentic, they are obviously not the cross itself. And if they were all genuine, then the original structure no longer exists. Yet in a sense, it still does; like how the finger of a saint can be revered as if it were the original person. Similarly for the historian, what matters is not the functional nature of the ark, but its physical nature. The ark can spend 20 years as a shed, but as long as the original material remains intact, it is merely a matter of reconfiguration.
Even if all that’s left of the ark is an unrecognisable portion of the stern, a museum can still proudly display the remains with a gilded plaque saying “This was the Ark of Noah”. They might even routinely disassemble the ark to move it from one continent to another, to tour the museums eager to exhibit it in blockbuster shows. They need only maintain its present state (e.g. arrest the decay as much as possible, don’t allow an artist to make a shed with it) to claim that it is still the same ship. Functionality is not essential to its identity; which is true in a sense, like how although Einstein’s preserved brain is no longer conscious, the fact remains that it had belonged to the great man. Its identity and provenance remain intact.
However, a person’s identity is unlike that of static, purely physical objects like holy artefacts or embalmed brains, a mind can change so much over time that it may seem paradoxical to consider him the same consciousness. Function takes on a more decisive role when it comes to dynamic phenomenon like a person’s consciousness.
This is similar to Aristotle’s view of the self. Unlike most people of his time, who believed the self to be an eternal soul separate from the body; Aristotle saw the self as a kind of embodied “activity” which makes something what it is. So the essence of a knife would be the act of ‘cutting’. The activity that defines a ‘knife’ is inseparable from the knife itself. So if a knife loses its edge for cutting, it ceases to be a ‘knife’ (here).
So if we took apart Theseus’s ship and built a house with the parts, the ship obviously no longer exists. A ‘ship’ has a different function from a ‘house’. A ship is transportation, it floats and ferries people across oceans; while a house is architecture, providing shelter on dry land. Their functions are radically different, so by definition they belong to entirely separate categories.
fig. 9: Scott Westerfeld’s ‘Leviathan’ (2009), an alternate steampunk history of World War I; where genetically engineered, hydrogen-breathing floating whales are used as living airships.
Yet we can imagine a conscious ship and sentient architecture endowed with futuristic Artificial Intelligence. In such cases, things would be different altogether. In terms of identity and selfhood, the ‘function’ that matters is not the intelligent vessel’s ability to stay afloat, but its capacity for consciousness. So “consciousness” is the definitive function of a brain, or any other sufficiently complex information processing system, it doesn’t really matter if it belongs to a spaceship, smart house, slime mould, jellyfish, man, woman, child or zombie. Even if a self-aware spaceship were slowly dismantled and remade into a building, it remains the same “experientially continuous” consciousness (as long as it continues to function the whole time).
So it appears that most of us do not really understand what makes us who we are. Another popular belief is that our ‘self’ is made up of our memories (which Parfit also argues), but even such an apparently commonsensical ‘truth’ seems to be mistaken.
Most scientists currently hold a strongly mechanistic and physicalist view of the mind, which they see as nothing more than the outcome of interacting atoms and molecules in the brain. Conscious experiences directly correspond to specific brain states, e.g. pain with the firing of certain neurons. The brain is just a highly complex computer, i.e. an information processing machine. This has led some to wonder if it might be possible to simulate people’s brain states (i.e. their consciousness) in a computer, thereby granting humans digital immortality. If the mind is just information, there seems to be no reason why this information can’t be faithfully replicated or “uploaded” into a computer.
fig. 10: 攻殻機動隊 Ghost in the Shell (1995).
However, there are some flaws in this computer-inspired analogy. It is impossible to “transfer” information from one medium to another, as if it were a liquid substance from one bowl to another, or a ‘soul’ passing between bodies. For instance, when we ‘move’ a music file from our thumb drive to our MP3 player, is it still the same file? It might seems so, because it is an exact bit for bit reproduction of that file. Unlike an analogue tape recording, the sound quality doesn’t deteriorate, so for most intents and purposes, it is the original file (posing a problem for music companies who respond with anti-piracy technologies like Digital Rights Management, which like the Theseus Paradox are concerned with the slippery definition of an ‘original’).
Yet it can’t be the same file. We now have two music files, so they can’t both be the same thing. Only one is the original. What happened was merely “copying”, a new file was written on the MP3 player’s memory, based on a description of the original thumb drive data. And when we delete the original file on the thumb drive, the illusion is complete; it seems as if the file had ‘transmigrated’ from the thumbdrive to the MP3 player. The illusion is even stronger if this happens gradually (à la the ship of Theseus). When we ‘cut-and-paste’ a file, nothing actually gets ‘cut-and-pasted’. The original file is just destroyed bit by bit while a new identical (but different and separate) file is being simultaneously duplicated in another location. This may not matter if it’s just an MP3 file, but when it’s someone’s consciousness, it is literally a matter of life and death.
The physicalist view of the “self” meshes well with our cultural emphasis on individuality. We are our personality, i.e. that unique, one-of-a-kind pattern of information encoded into the neurons of our brains. Therefore, if we can duplicate exactly this pattern, the resulting copy would be “you”. If scientists are right that the mind is just a pattern of brain states unique to each person, then it is also possible to imagine an ‘atom copier’, i.e. a machine that can scan the arrangement of all the atoms making up your body, and rebuild an exact copy using new atoms. This will create a strange situation where the resulting clone will have all your memories, yet is obviously not you.
Suppose we broke into a Mr. and Mrs. McCoy’s house one night and performed this procedure on the unsuspecting husband who is in a deep sleep. When the wife wakes up in the morning, she finds two husbands. But which is the person she married? Does it even matter? According to the physicalist, both of them are, for all intents and purposes, exactly the same. Yet most of us would think it does matter, because the perfect clone is nothing but a creepy imposter.
Unfortunately for the poor wife, there would be no way to tell them apart. The atomic clone would inherit all the memories of the real husband, everything from his childhood, to the most intimate details of their courtship, to the fact that their son has an appointment with the doctor next week, right up until the moment he ‘fell asleep’ that night. And the clone would truly believe that he is the genuine Mr. McCoy, even though he didn’t even exist before he ‘went to bed’. This strange being would be as upset and distressed as the real husband, because he remembers clearly the life he never spent with this distraught woman he thinks is his wife. And who’s to say the same thing didn’t happen to us last night? In fact, we have no way of knowing that just by resorting to the fact of our memories.
fig. 12: In Christopher Nolan’s ‘Memento’ (2000), a man loses his memory every time he wakes up, so he tattoos messages all over his body to maintain his sense of self. Another word for memento is ‘relic’, like our ship of Theseus.
Although the clone has the complete memories of the original, he is not the same “self” as the original. Conversely, suppose every time we go to sleep and wake up, we forget who we are, we lose all our memories. Even then, our experience of consciousness remains unbroken. If I pricked you with a needle, you are the still the one feeling the pain. It won’t mean that you die every night and a different person wakes up every morning. So it seems like our memories are ontologically irrelevant to who we are. Consciousness is an aggressively ‘now’ experience, fluctuating from moment to moment, while memory is a static, stable construct of the past, and we mistakenly assign to this accumulation of passed moments the identity of a “self”.
This presents an acute problem for the Singularitarian dream of immortality. Singularitarians believe that in next 50 years computers will surpass human intelligence and lead to an inconceivable explosion of technological progress (an event they call the ‘Singularity’). One of their predictions is that we will finally possess enough computing power to ‘reproduce’ the human brain in digital form. Some of them believe that it will be possible to scan a brain with a laser beam, capturing information about the exact arrangement of atoms and cells layer by layer and modelling that data on a powerful computer, as a virtual brain. As the information is built up in the computer, the person’s flesh brain would be burned off layer by atomic layer. The result will be that the person’s consciousness, memories and his ‘self’ are digitized and transferred into the computer.
Yet as we’ve seen, even if the resulting virtual brain were conscious, and has the same memories, it still won’t be the original person but a new one; because ‘experiential continuity’ is violated. Therefore, far from being a means to immortality; “mind-uploading” would be more like murder. No matter how advanced technology accelerates during the Singularity, mind-uploading seems doomed to fail.
A more promising road to immortality may be cyborgization, where a person’s brain is slowly replaced with more durable, perhaps nano-technological components; without disrupting his ‘experiential continuity’. The end result may be more machine than human, but you would still be you; as with the Tin Man in ‘The Wizard Of Oz’, and the man in our Kafkanian “slug metamorphosis” case.
Indeed, some thinkers have proposed a thought experiment which purports to show that Parfit’s ‘psychological continuity’ is not enough for the self to persist. To some extent, it also threatens the ‘experiential continuity’ view.
The reasoning goes like this. According to the ‘psychological continuity’ theory, if your brain were transplanted into another person’s body, the new being would still be you. And if half your brain is destroyed, like in hemispherectomies for inoperable brain tumours, you would also still be you (albeit with some diminished mental ability). But what if we halved your brain and transplanted each hemisphere into two different bodies? The ‘psychological continuity’ criterion says that any state which is psychologically continuous with you must be you. Since both the left brain recipient and the right brain one are ‘psychologically continuous’ with you, then they must both be ‘you’, which is absurd. When we tickle Mr. Left Brain, Mr. Right Brain wouldn’t feel ticklish, so they can’t both be you. Therefore ‘psychological continuity’ is contradictory.
Other philosophers (here) have taken this mean that ‘psychological continuity’ alone is not enough for the self to survive. So when your brain is transplanted into two people, you actually die, and neither of the two recipients are ‘you’, but new selves. To save the ‘psychological continuity’ criterion from contradiction, they add that it must be exclusive. You survive only if half of your brain is transplanted, and the other is destroyed; but you cease to exist if both are transplanted. Which sounds even more absurd.
Again, this is another example of ‘category blindness’. Their worry isn’t really about continuity, but uniqueness, i.e. our personality, memories, brain-states, and other patterns of information encoded in our neurons. That seems to be what they understand by ‘psychology’, a list of attributes to be ticked off, that make a self what it is and not another. So when there are two selves that are practically the same, uniqueness is threatened. There seems to arise a contradiction, because the self is supposed to be a category of one. How can we decide which one is the real ‘you’, or if you survived at all?
I would suggest that the contradiction is merely apparent, and can be easily resolved if we let go of our intuitive attachment to the idea of uniqueness and individuality. In fact, the ‘split brain transplant’ case is just a dressed-up version of the ‘atom copier’ case. In the case of the atomic clone, we also have two exactly identical people, yet nobody seems to be troubled, because there isn’t in fact any physical contradiction. The only problem is that no observer can tell who is the original (because the clone will have pseudo-memories), but that doesn’t mean that there are now two ‘yous’. The consciousness of the original ‘you’ continues unhindered, it is not affected by the commencement or addition of a new franchise to the world.
But one might argue that there is in fact some difference. The atomic cloning technicians could have taken precautions, e.g. they might have tagged or tattooed the clone when he rolled out of the machine; so there might be some way of telling which is the original or new ‘you’ (though that will be less fun). This is impossible for the brain splitting surgeons, because a single ‘self’ is transplanted into two bodies. There seems to be no criteria imaginable for deciding which is the original consciousness, if it survived at all. But as with the atomic cloning case, we may be confusing “unknowability” with “contradiction”.
For instance, if a brain tumour patient undergoes a hemispherectomy, in which one brain hemisphere is surgically removed, few would think that when he wakes up, he is replaced by another person. Yet it could be that there is really no difference between real-life hemispherectomies and the science-fictional ‘one brain/double body’ transplant case. When the cancerous half-brain is removed from the skull, not only does it contain part of the memories and personality of the patient, it also retains the potential for consciousness; and if we could transplant it into a new body or machine, we’ll get a new person. Of course, we have no such technology. In real life, hospitals would just unceremoniously throw away the half-brain as medical waste without a second look, like an amputated limb. Yet it could be that a second self is created each time in every hemispherectomy, but it’s just that the half-brain is not immediately connected to a life-support system, so the new (unconscious?) self survives for only a short while before “dying”. So all hemispherectomies may be a form of abortion. Even when the patient survives, the other newly created ‘continuum’ is denied the right to continue existing, like an aborted foetus. But in any case, the original ‘psychological continuum’ remains undisrupted, even if a new “self” is created by the split.
However, there’s a problem. There is no difference between the two halves of the brain. What if the doctors accidentally removed the healthy half of the brain instead? Suppose a new “psychological continuum” is created every time a brain is split. There seems to be no reason to stop the patient’s original ‘psychological continuum’ (or ‘experiential continuum’) from “following” the half that ends up in the rubbish bin, rather than choosing the half that remains attached to the body. There seems to be an equal chance of either one happening.
If the new “self” ends up in the hemisphere attached to the patient’s body, and the original “experiential continuum” ends up in the excised hemisphere; we’d have no way of telling. The new “self” would think that it is the “original”, because it would have part of the memories of the original continuum (which is now trapped in the discarded hemisphere), just like the husband’s perfect clone in the ‘atom copier’ case.
However, unlike the atomic clone, it would be wrong to say that the new “self” created by the operation has ‘false memories’. Because unlike duplication, where a wholly new entity is created from nothing, the newly born half-brained “experiential continuum” isn’t. It was created by ‘fragmentation’, i.e. it was once continuous with the original. In that sense, what it remembers are what it genuinely experienced once upon a time. It’s like cloning, but involving a loss to the original. Something new is created from a diminishing of the old, rather than from nothing.
Suppose a man gets involved in a horrific car accident, and half his brain gets splattered all over the tarmac. Common sense would say that the original “self” is the injured man who lost half his brain, rather than the pieces of brain matter sticking to the road. Few would think it is possible for the man’s original experiential or psychological continuum (his self) to have “followed” the ejected brain matter, and that the man lying on the street is actually a whole new being created by the accident. Most of us would think that the man is just injured. Even if the ejected brain gunk were salvaged by doctors and successfully transplanted into another body, our intuitions would remain the same.
The question of originality is a larger headache that goes beyond merely consciousness. It’s a “half empty/half full” kind of conundrum, what philosophers call a ‘sorites paradox’. For example, if we were to remove from a heap of rice one grain of rice at a time, over and over again, at what point will the heap cease to exist? Can there be a “heap” of just three, or one grain of rice? There seems to be no clear cut-off point where the heap ends and individual grains begin.
Similarly, we can saw off one leg of a chair. Intuitively, it seems obvious that the original chair has lost 10% of itself. Yet it is just as reasonable to point to the leg and call that the ‘original chair’ which has lost 90% of itself. But most would argue that the leg is just a ‘component’ of the chair. After all, ”chair” is defined by its function, and you can’t sit on just the leg. The three legged chair may be a little shaky, but it is still a chair. But what if we split the chair exactly down the middle into two equal halves? Which is now the original chair? Or is it no longer a chair? What if we incinerated the other 90% of the chair, does the surviving 10% then become the “original chair”?
Again, physical objects may be a poor analogy for consciousness. Though you can’t sit on a fraction of a chair (which is no longer a “chair” but a “part”); the function of consciousness seems to survive some degree of destruction (as in the case of hemispherectomies). Perhaps consciousness is more like a mirror. You can shatter a mirror into ten separate pieces, but each piece continues to function perfectly fine as a reflective tool, albeit with less area (or capacity). Another analogy would a ceramic bowl. When sliced in two, the surface curvature can still be used to hold some water, but in lesser quantities than the intact original. Each half can still be considered a functional (albeit unconventional) bowl.
Also, we do not need to say that there were 10 smaller mirrors hidden in the original mirror, or two bowls hiding in the original bowl. It was one seamless, continuous substance. Similarly, just because a new “experiential continuum” is created by a split-brain transplant doesn’t mean that there were two selves in the original brain to begin with (a bizarre view called the “multiple occupancy” position, here).
To ask which hemisphere is the original “psychological or experiential continuum” is as problematic as asking which half of a precisely bisected bowl is the ‘original bowl’. Unlike the catastrophic failure of the bisected chair, both bowl halves continue to be functional in a diminished way. Interestingly, when holograms are shattered, each fragment similarly contains the exact same image (but with a lower resolution) as the original hologram. Consciousness might have similar properties.
Unlike the split brain operation, where one or both hemispheres need to be transplanted into a new body, we can make it more straightforward. Imagine an immortal being like Wolverine from the X-men who remains alive even when sliced down the middle into half. If we tickled one half, the other half will not feel ticklish because they are no longer connected. Has Wolverine survived? Or did he die? Are there now two new Wolverines? Yet both halves seem to possess the motivations, memories and personality of the old Wolverine. If the original Wolverine “died” in the bisection, what if we brought the newly independent halves together? Due to his mutant powers of injury recovery, the two halves would seamlessly fuse back together into one. Has the original Wolverine’s “experiential continuum” somehow popped right back into existence again? Or is it a different, newly created Wolverine?
fig. 15: The Animatrix (The Second Renaissance), robots experimenting with bisected humans who are kept alive.
In fact, there is no need to imagine such a counter-intuitive scenario, because fact is indeed stranger than fiction. There already exists in nature a creature with such bizarre abilities — the Planarian, or flatworm. If you cut one cross-wise or length-wise, not only will it be unimpressed by your harassment, each section will regenerate into a complete individual, as if nothing had happened.
They are born in a strange way, by fission. In a process called architomy, the body constricts just behind the feeding tube (pharynx) and the lower body anchors itself to a rock. After a few hours of tugging, the worm rips itself apart at the waist, dividing into a nearly normal front half with the head ganglion (a primitive brain), eyes, pharynx, most of the gut; and a headless backside which goes on to lead a new life. It will eventually regenerate the missing organs, including a new head and brain. Unlike budding (a type of paratomy) in hydra, in architomy the organs for the new half are not formed prior to fission, but after. After division, the front half behaves normally, but the back half remains immobile until the brain, eyes and feeding tube are regenerated. After two weeks, we get two smaller individuals that will eventually grow back to the size of the original worm (video here).
Some animals are capable of unidirectional regeneration, e.g. lizards regrow their tails, and crabs regrow missing claws; but a new crab won’t grow out of a severed claw. Flatworms are capable of bidirectional regeneration. It would be like cutting a leg off a chair, and not only does the damaged chair regenerate a new leg; the severed leg also regrows an entire new chair. In fact, the geneticist Thomas Hunt Morgan was astonished to discover in the 1800s that you can dissect a flatworm into a maximum of 279 pieces, and each fragment will grow back into a complete individual (which would strain the ‘multiple occupancy’ view, if flatworms are conscious).
fig. 17: If you bisected just the head of a planarian, you will get a two-headed worm.
Nobody can say for sure if planaria are conscious or not, but they do seem to react to their environment in a volitional manner like more complex organisms, e.g. when looking for food, or mates for sex (they can reproduce both ways). They can also be taught to travel through a maze to find food (like dogs or mice), or be conditioned with light to behave in certain ways. Such behaviour modification is a form of memory and learning. And since they have densely packed and complex interconnected neurons in their ‘ganglionic neuropile’ (here), the least we can say is that they are capable of having brain-states. So it is conceivable that they may experience some form of primitive consciousness.
Which brings us back to our paradoxical scenarios. If you cut a planarian cross-wise, I think it’s safe to say that the ‘experiential continuity’ stays with the head, because for the first few weeks the tail portion shows no signs of any activity, so we can say it is non-conscious. It would be like amputating Wolverine’s arm, and a new being grows from the non-conscious body part. It would be like how normal humans develop from an unconscious fertilized egg. In terms of ‘experiential continuity’, nothing mind-bending.
fig. 18: The planarian nervous system.
But things get freaky when we cut it length-wise. It becomes less straightforward which side (left or right) is the original ‘experiential continuum’. Furthermore, individuals regenerated from fragments of a previously trained planarian will retain the memories of the original; probably because its brain is the entire nervous system distributed across the body, and not just the ganglion mass in the head.
It could be that a new ‘experiential continuum’ is created from part of the original ‘consciousness’. Like amputation, but involving the brain and mind. From the point of view of the original mind, it lost a part of itself. But from the perspective of the newly independent, disconnected mind; it will think the same thing, will feel it had always existed (because it has access to certain memories of the original). If a brain or flatworm is divided into two equal halves, all we can say is there’s a random chance which half is the original ‘experiential continuum’ (like breaking a hologram in two, and it makes no practical difference anyway since they are psychologically identical). But since only one extra mind is born, there is no paradox.
Similarly, suppose a Chinese accountant had her left brain hemisphere removed from her head, and an American concert pianist had his right brain hemisphere removed from his. Her left half is then transplanted into his half-empty head, and his right half into her’s. We can only imagine how this would wreck havoc on both their ‘selves’, e.g. how their new brains, which are a fusion of two brains, would reconcile the conflicting memories and personalities. Perhaps the accountant would be perplexed by her new-found virtuosity at playing the piano, and the pianist by his ability to speak Chinese. Yet even in such a drastic case, ‘psychological and experiential continuity’ would still be preserved. Both original ‘experiential continua’ had merely received new psychological input. It will be like brain injury, but in reverse. Something is gained rather than lost, but as with brain injuries, it threatens neither ‘psychological’ nor ‘experiential continuity’.
It seems that the more we think about the self, the more it slips through our fingers. Which is unsettling, given how the self is the basic assumption around which we construct our lives (especially in Western culture). So far, we have eliminated seemingly obvious requirements, like psychology, memory and uniqueness. It seems like ‘experiential continuity’ is the only necessary condition for the “self” to carry on existing. Yet what exactly is this ‘conscious experience’?
The Buddha seems have understood the inherent difficulties in properly grasping these paradoxes. When asked if the person reborn in the next life is the same person or a different one, he gave the enigmatic reply, “na ca so, na ca anno”; or “not he, yet not another”. In not giving a straight answer, the Buddha wasn’t just equivocating or deliberately wrapping the issue in obfuscation; but was trying his best to express a complex idea using the inadequacies of language and ordinary thinking.
Since Buddhism rejects the conventional understanding of a ‘soul’ as false, how can rebirth take place? What gets reborn if there is no such thing as a separately existing, eternal ‘self’? Since ‘experiential continuity’ seems to be nontransferably yoked together with our biology (like an MP3 file on a thumbdrive), wouldn’t our consciousness end with the death of the brain? Yet even though the Buddha “attacked all attempts to conceive of a fixed self”, he also warned that the view “I have no self” is also mistaken. As the Buddha hinted in his seemingly paradoxical reply, there is more than meets the eye. To do justice to the nuances and complexities involved would require an entirely separate article, so we will leave this problem for an upcoming entry, building on what we have discussed so far.
fig. 1: <http://www.abc.se/~m10354/uwa/whatis.htm>
fig. 2: <http://www.thew2o.net/content/maritime-traditions>
fig. 3: <http://www.myfreewallpapers.net/movies/pages/wizard-of-oz-black-and-white.shtml>
fig. 4: <http://www.hifructose.com/the-blog/1239-an-interview-with-scott-campbell.html>
fig. 5: <http://2.bp.blogspot.com/-t6HqPOBi46Q/TaCKQ_9rEhI/AAAAAAAAK9M/6MWNwMmx_Hc/s400/hammerhead+shark+attack.jpg>
fig. 6: <http://chestofbooks.com/animals/zoology/Life/Plate-V-Cellar-Slug-Limax-Flavus-S-Variegatus.html>
fig. 7: <http://www.we-find-wildness.com/2010/07/simon-starling/>
fig. 8: <http://www.adiyamanli.org/agri.html>
fig. 9: <http://libraryofcleanreads.blogspot.com/2011/04/leviathan-by-scott-westerfeld.html>
fig. 10: <http://homecinema.thedigitalfix.com/content/id/71703/ghost-in-the-shell-20.html>
fig. 11: Own.
fig. 12: <http://movie-sakura.cocolog-nifty.com/blog/images/2007/10/19/memento.jpg>
fig. 13: <http://www.britishmuseum.org/collectionimages/AN00063/AN00063598_001_l.jpg>
fig. 14: <http://mmoccforum.com/Thread-Office-Computer-Chair>
fig. 15: <http://www.rottentomatoes.com/m/animatrix/>
fig. 16: <http://www.nos.org/bio12/b4h26.1.htm>
fig. 17: <http://users.design.ucla.edu/~tatsuyas/classes/152BC/ex3/index.htm>
fig. 18: <http://www.rzuser.uni-heidelberg.de/~bu6/Introduction12.html>
fig. 19: <http://en.wikipedia.org/wiki/File:Buddha_nobletruths.jpg>