Between the times of our birth and our death, we undergo huge changes. Our bodies change substantially, with every one of our cells being replaced several times during our lifetime. Similarly, our memories, personality and entire psychology change, often drastically, throughout our lives. In the face of such extreme changes, what claim can we possibly have to a single identity which remains constant throughout?
What practical implications will the solution have?
This may sound like a needlessly ‘deep’ philosophical question, and many may claim that we can easily tell that we are the same person we were yesterday so there cannot be a problem. Yet there is a huge practical need for us to ascertain appropriate criteria for identity over time, and there are wide implications for the enforcement of such criteria. For example, we may find that some people are so vastly different from their past self that to punish them for the crimes committed in the past would not be just. Another important implication comes in ascertaining whether or not someone’s will or advanced directive should be followed. If it can be shown that this person was not ‘himself’ when he wrote such documents, we may deem it unsuitable to follow it.
How the problem may be addressed
Roderick Chisholm claims that when we speak of our identity with our past or future selves, we intend it in a strict sense, whereby we mean that we are exactly the same. The changing of our cells, however, eliminates us from Chisholm’s criteria for strict identity, meaning the only identity we can hope for over time is a loose one (Chisholm, p. 82). Similarly, the vast amount of changes we endure exclude us from qualitative similarity. For this reason, I am interested in how one can be said to maintain numerical identity throughout their life.
In this essay, I examine various suggestions for criteria for the continuation of one’s identity. These suggestions often tend to fall under two broad categories: bodily continuity or psychological continuity. I also investigate a suggested refinement of the theory of bodily continuity which uses the brain as a criterion for continuity, as well as the memory criterion for continuity. There have been further proposals which do not fall into either of categories above, such as David Hume’s Bundle Theory of the Self. I will not be addressing these approaches, as I wish to identify a set of clear-cut criteria which can be used to ascertain the status of one’s identity and can be utilised in a real-life setting.
Aims of this essay
As I consider the arguments for and against each of the four criteria, I intend to ascertain which elements of our identity should be considered essential and which must, therefore, be covered by whichever position we eventually decide to adopt with regards to personal identity over time.
In this chapter I will demonstrate, through describing the limits of acceptable physical change, that the bodily criterion alone is not sufficient for the continuation of one’s identity. However, I will also show that some form of physical continuation is necessary, such as a person’s genetic make-up.
The Bodily Continuity Criterion
Some materialist philosophers (such as Eric Olsen) have claimed that the physical body is the seat of the identity. This view claims that as long as one keeps the same body throughout their life, they are guaranteed to maintain their unique identity.
This approach makes identifying selves clear and simple, as we can identify the exact spatio-temporal location of each self, as well as the starts and ends of selves. So, for example, if someone commits a crime, we can easily establish whether they are guilty or not by evidence such as fingerprints and witness testimony. As long as their body committed the crime, we are able to punish them for it.
Criticisms of this position with regards to change over time
There is a lot of opposition to the view that our identity should be limited to just the physical body. This position is contrary to most religions, which view our immaterial souls as intrinsic to our identities. The religious conception of a soul tends to be like that of consciousness, and some religions, such as Judeo-Christian religions, claim that this part of us continues to live on after the physical body has died. As Derek Parfit points out, though, the bodily criterion would only allow for a second life in the form of a physical resurrection or reincarnation (Parfit, p. 204). However, we certainly should not dismiss the bodily criterion simply because it is incompatible with popular religions.
There are more damning criticisms of the bodily criterion for identity, though. Our bodies are constantly changing- growing, shedding or regenerating cells, etc. So how much of our body must stay the same in order for us to be classed as the same person we were several years ago? For example, a popular analogy was given which describes the philosopher John Locke’s favourite pair of socks, which grow holes in from being worn so often. As the holes develop, Locke repairs them with patches. But after a while of repairing his socks, none of the original material remains, and they are simply a patchwork of new pieces of material (Parker, p. 552). The original debate, of which Locke’s example was a variation, is that of the Ship of Theseus, which has its pieces replaced one at a time, as necessary (Leibniz, p. 231). Many people believe that, at some point, the Ship of Theseus loses too many of its original pieces and ceases to be the same ship that Theseus had returned from Crete in. Similarly, some believe that Locke’s favourite pair of socks cease to exist when none of the original yarns are present.
But, if we are to equate identity with the body’s cells, these examples suggest that we must develop a new identity as our bodily cells change during our lifetime. This is a bizarre position to hold, as there would be no detectable change in our appearance or attitude. An implication of this would be that we should not punish a 60 year-old for the crimes he committed when he was 20 years old, as his body is not the one which committed them. While there may be a great amount of difference between his past self and himself now, it still seems absurd to decide his body’s cells are the most important aspect, rather than, perhaps, how likely he is to re-offend.
Possible solutions to criticisms, and the success of these solutions
But not everyone agrees that this is the case. Many people believe that the gradual change involved in the previous examples ensures that they retain their former identity. In the case of Locke’s socks, the consensus tends to be that the resulting pair of socks are indeed the same as his favourite pair of socks, as this is the way we speak of things which have been repaired. Similarly, the gradual change of the Ship of Theseus ensures it retains its identity. As this pertains to the body, it suggests that, despite each of our cells being regenerated every seven years (Marohn, p. 88), this does not inhibit us from remaining the same person. This means the gradual change of our body’s cells falls within the acceptable limits of change, apparently saving the bodily criterion for identity.
The need for gradual change is supported by Parfit’s teletransporter thought experiment. He describes a machine which transports people to Mars by recording the position of every cell in their body, then destroying the body and building one exactly similar on Mars. But one day the machine is changed, and no longer destroys the Earth body, but causes cardiac problems which lead to death in a few days. Parfit states that the person on Earth would believe they are to die, because the individual on Mars is simply a replica of their true self (Parfit, pp. 199-201).
Roderick Chisholm offered another variation upon this theme, whereby the ship’s planks are replaced with aluminium (Chisholm, p. 273). The pieces removed from the ship were then reassembled to form a ‘replica’ ship. But in this example, we are more inclined to state that the ‘replica’ ship which has been assembled from the original pieces is the same ship of Theseus, while the aluminium repairs have become a replica.
This is perhaps because a crucial part of the theory of bodily continuity is that it requires we maintain essentially the same genetic structure. This makes the concept of bodily continuity highly supported by the sciences, which tend to view us as biological creatures governed by the physical reactions which occur within our brains. A result of this is that, while our bodies could be perfectly and entirely replicated in a metallic form, these robots would lack our genetic code and would thus be a replica, rather than ourselves.
Genetic determinism takes this position further, and claims that who we are is entirely dependent upon our genetics. Because of this view, it seems genetic determinists must hold that a clone would be identical to the person he was cloned from. However, we must draw the distinction here between qualitative identity and numerical identity. Identical twins share 100% of their genes, but this could only make them qualitatively similar, never numerically identical.
The acceptable limits of change
So we have established that the gradual regeneration of our cells during our lives falls within the realms of acceptable change, whereas being entirely replaced with a non-human body (for example, a metal one) does not.
So where exactly are the boundaries for changes we deem to be acceptable? How much of our body could we lose without losing our identity? Bernard Williams describes a thought experiment where a person’s body is replaced very gradually with that of Napoleon’s. Williams claims that this example is subject to the heap paradox (Parfit, p. 234). In the same way removing a grain from a heap does not stop it from being a heap, it seems that each change is too small to change our identity. Yet by the end of the experiment, the person’s body has been replaced with that of Napoleon’s.
In this example, Williams describes the physical changes which occur to the subject of this experiment, but not the psychological effects. It seems that the information we need in order to ascertain whether or not the subject is still the same person after the experiment as before is regarding his memories and character traits. While being given Napoleon’s arms and legs seem to be of little consequence to his identity, being given his brain is much more significant. This suggests that the brain is the only part of the body necessary for identity continuity.
While this is a very radical example, it does have practical implications. If a certain amount of our body is required to stay the same for us to remain the same person, this raises questions about amputees and people who undergo extensive plastic surgery. For example, what if a man had his arms amputated, and then his legs? Would he still be the same man he was prior to these operations? While he may now lack many of the skills he had before, it seems unfair to claim he is not the same man. What if he was somehow reduced to simply a head in a jar, though, and was connected to machines to keep him alive? It seems that perhaps the only part of the body which is necessary for the continuation of one’s identity is the brain.
This proposal was supported by Sydney Shoemaker, who raised the following thought experiment as an objection to the bodily criterion. Shoemaker describes a thought experiment regarding two men, Brown and Robinson, who undergo brain transplants. Brown’s brain is placed into the body of Robinson, and vice versa. When Robinson’s body awakes, he remembers everything of Brown’s life, behaves like Brown, has the same beliefs as Brown, and even adopts all the mannerisms his family have come to associate with Brown. It seems that Brown and Robinson’s families alike must agree that Robinson’s body is now home to Brown’s identity (Shoemaker, p. 43). While this is a very extreme case, it does demonstrate that the body alone is neither a sufficient nor necessary condition for the continuity of one’s identity, and that the brain may be a better candidate.
Eric Olson defends the bodily criterion against this criticism, viewing the individual simply as a biological organism. He claims that humans can withstand complete psychological change and remain the same as long as they are alive for (Olson, p.131). I disagree with this position, however; it seems to me that if you remove a person’s personality, mannerisms, memories, dispositions, etc, you have removed that person’s very identity. In considering the individual as a human animal, Olson appears to have oversimplified the issue of identity. It is easy to say that the human being still exists despite this overhaul of their mental life, but it is very difficult to substantiate the claim that their personal identity has not been at all affected by this.
In this chapter I will demonstrate that the brain is the only physical element that is needed for one to maintain their identity over time. However, this is simply because it is home to the most important element of a person’s identity: their psychology.
The brain continuity criterion
It seems that the bodily continuity theory could be refined and focused to one crucial part of the body: the brain. The brain holds all of the information we consider crucial to our identity, such as our memories, beliefs, opinions, passions, dispositions, attitudes, etc.
As we have seen, a key proponent of this position is Bernard Williams. Williams’ thought experiments describe numerous small changes which, when taken individually, appear to make no difference to one’s identity. However, these small changes combine to utterly transform the individual. Parfit states that if there is some point between the start and the end of the experiment where the original person dies, the difference between life and death must be incredibly incremental, and impossible to define, just as the distinction between a few grains and a heap (Parfit, p.244). Because of this, Williams believes that identity should be reduced to one functioning brain (Noonan, p. 7). This simplifies the matter of identity, allowing for a clear definition which can be easily implemented. So, for example, an old man can easily claim he is identical with his younger self if they share the same functioning brain.
A flaw with this position
At first, it appears that the brain gives us a clearer way of defining identities than trying to ascertain how many of a person’s cells have regenerated, as the brain is either present and functioning or not.
However, it is possible for people to survive with only half a brain. So, as long as both halves of my brain are equally well-developed, one half of my brain could theoretically be transplanted into the body of another person. One problem with the brain criterion is that it leaves open the possibility that one person could be identical with more than one individual in the future if they were to undergo a partial brain transplant. Yet, as mentioned earlier, we are concerned with numerical identity over time, and it is not possible for one person to be numerically identical with two people. If we wish to avoid this problem for the brain criterion, we could claim that half a brain is not enough for me to hold onto my claim to my identity. If this is the case, I would effectively die when I underwent the procedure. But if we take this position, what do we say of the two individuals who walk around with my brain? It seems that, by this criterion, we would be forced to say that two new identities have somehow arisen, with my memories and much of my personality. This is an absurd position to defend, suggesting that the brain criterion needs refining.
So if the brain criterion cannot settle the question of what happens to me after this procedure, what can? In order to save ourselves from these problems, it seems our best option is to return to the bodily criterion. This additional criterion allows us to distinguish between the two identities, by stating that I have awaken in my body with half of my brain, while someone else has awoken in their body with the other half. This is supported by our conclusions from chapter one, where we found that our genetic code is of some significance to our identity.
Criticisms of this position with regards to change over time
A possible implication of this theory is that brain damage would change our very identity. It is true that severe damage can certainly have a profound impact upon our identity. For example, many people claim that patients in the later stages of Alzheimer’s disease are no longer the same person they used to be. Yet many people have suffered brain damage which has only affected a very localised area of the brain, leaving them otherwise exactly as they were before the incident. For example, when damage to the fusiform gyrus occurs (sometimes associated with a stroke), some people have been left with prosopagnosia- the inability to recognise faces. They are otherwise completely cognitively normal, with no other areas of vision or recognition affected (Kalat, p. 175), leading us to feel that they are still the same person as they were before the injury.
We could ask how much of the brain one needs in order for his identity to continue.
This evidence seems to suggest that there is either a certain amount of brain damage which we can endure without it affecting our identity, or that there are only certain areas of the brain which are responsible for the characteristics we consider essential to who we are. But it seems the issue is not one of ascertaining what percentage of the original brain is needed, but which areas of the brain are essential for the continuation of our identity. There is some instinctive support for this claim, as it seems that while sight, hearing, taste, smell can be lost without particular consequence to our personality, a drastic change to dispositions and temperament would pose a much higher threat.
The problem of identity over time can then be broken down into two questions. Firstly, which elements of our psychology are essential constituents to our identity? And secondly, should an explanation of identity over time appeal to the organic structure of the brain, which is necessary to realise the psychology of an individual, or directly to the psychology itself? Let me illustrate this distinction with an example. In Williams’ thought experiment, a man’s body was gradually replaced with that of Napoleon (Parfit, p. 234). It seems that replacing the subject’s brain with that of Napoleon will result in the loss of his identity. But we could imagine that the cells of the subject’s brain were replaced by those of Napoleon’s brain, while the structure remained as similar as possible. If this were the case, it is possible the subject would maintain the aspects of his psychology which are necessary for him to maintain his identity. Because of this, it seems likely that the organic matter of the brain is not so important as the psychological contents of it, which could be realised by other materials. So in the future, it may even be possible for the structure of our brains to be built from non-organic materials, such as metal, which would allow a computer to operate in the place of our brain.
In the rest of this essay I focus directly on the psychological elements of identity in order to establish which elements may be necessary for the continuation of our identity. In my conclusion, however, I further address the distinction between psychology and the substance which realises it, and explain why psychology is currently the best option for a necessary condition of identity.
In this chapter I will demonstrate that memories are very important to our conception of ourselves and the identities of others, but are unreliable and not alone sufficient for ensuring the continuation of one’s identity. I believe that more psychological elements are required in instances where memories are erroneous or have been forgotten.
Locke’s theory of personal identity
John Locke argues that it is not the brain itself which is the key to identity, but what the brain holds: our consciousness (Locke, p. 71).
Consciousness is a difficult term to define though. Thomas Reid points out that we cannot be conscious of the past, as you can only ever be conscious of the present (Reid, p. 222). So perhaps Locke means that it is our memories which make us the same person as we were yesterday. The problem with this is that I can remember what my flatmates were doing yesterday, but this does not make me identical with my flatmates. So it must only be first-person memory, from my own perspective, which demonstrates that I am identical with myself from yesterday. Joseph Butler objects that this results in a circular position, as having first-person memories of actions implies my remembering that I performed them (Butler, p. 324). However, we can see that it would be possible for someone to wake up with amnesia, knowing what actions they had performed recently but with no idea who they are. Thus it is possible to separate first-person memory from identity. This is, therefore, the position popularly attributed to Locke.
Criticisms of Locke’s account
But does this mean that I cease to be myself when I sleep, or that when I temporarily forget that I went cycling yesterday I am no longer the person who went cycling yesterday? Locke would not believe this to be the case. As long as I remembered when I was prompted or woken up then I would still be the same person.
But what if I could not remember, even with prompting? For example, someone with Alzheimer’s disease may suffer loss of memory of recent events. There was also the case of David Fitzpatrick, who suffered a dissociative fugue at age 25, causing him to forget everything about his life before the fugue (Channel Five’s “The Man With No Past”). As Locke’s theory of identity related to the responsibility of the agent, Locke would have to say that David Fitzpatrick could not be held responsible for any of the actions, good or bad, he had carried out prior to his fugue.
We are reluctant to accept that people are not responsible for actions they cannot recall committing, however. A distinction which needs to be drawn in Locke’s position on accountability is the difference between being conscious of an action now and being conscious of it when it was being committed. For example, Jules Lowe was not convicted of the murder of his father because he committed the crime while asleep (Smith-Spark, online). Since he was clearly not conscious of the actions he was performing, he was not held responsible for them. However, someone who intentionally hurts many people and later forgets what he has done should certainly not be deemed innocent.
As this pertains to identity, we can see that there may be parts of our lives we can no longer recall. For example, most of us recall very little of our early childhood. Thomas Reid objects to this element of Locke’s theory of identity with a famous example. A young boy is flogged for stealing apples, grows up to become an officer and later becomes a general. The officer remembered being flogged, and the general remembers being an officer, but the general does not remember being flogged. According to Locke this means the general is not the same person as he was as a child. Reid argues, however, that, although memory continuity is not transitive, numerical identity is (Reid, p.249). A related concern is that I can never have memories of times when I am not conscious. This has the peculiar implication that it is not me who sleeps in my bed every night, but someone else.
These issues can be addressed, however, by distinguishing between the notions of psychological connectedness and psychological continuity. Person A is psychologically connected with Person B if his psychological states are the same of those of Person A. On the other hand, Person A is psychologically continuous with Person B if his mental states are related to those of Person B, by an overlapping chain of connectedness. In this way, while the general is no longer psychologically connected to himself as a young boy, he is still psychologically continuous with him.
A significant problem with Locke’s theory is the possibility that one may have memories which have become distorted over time, or altogether false. Memories are extremely fragile, and easily led by suggestions from others. For example, David Bjorklund found that it is possible for researchers to manipulate subjects’ beliefs about events simply by offering reasons for the inaccuracy of their memories (Bjorklund, p. 53).
Locke explains that, in the case of one who falsely suffers guilt for someone else’s crime, when we get to Heaven, God will ensure that the only memories we have and can be held responsible for are our own (Locke, p. 473). But in order for God to determine which memories are ours, he must be able to determine who we are. Locke is unable to explain how God’s criteria for identity differs from, and is more effective than, Locke’s.
A similar problem for Locke is cases of amnesia, whereby a person forgets everything of their past. A new person may seem to emerge after the episode, perhaps if a previously extroverted person then develops a very shy and reserved character. But what if they later recovered their memory and returned to what we would consider their usual selves? It is difficult to ascertain how we should speak of those who have forgotten who they are. If we describe their identity as effectively dieing, it seems they would somehow come back to life when they regain their memories. In times of temporary memory loss, it seems we must return once more to the physical body for some sort of continuity until their memories return.
Tan Tai Wei supports this position, stating that the unreliability of memories means that we need more in order to assure one’s identity. He claims that our bodies are necessary for the authentication of our memories (Wei, p. 33). As demonstrated in previous chapters, the only important aspects of our body are the brain and our genetic make-up. Yet these do not seem to offer any reliable authentication of our memories.
Yet in the face of memory loss, people do not become a tabula rasa. Even if they remember nothing of their life, they have a temperament, likes and dislikes, etc. These seem to offer an improved continuity of their identity. I believe this is because what we ourselves would deem important for the continuation of our identity is our psychology: our beliefs, opinions, attitudes and passions.
In this chapter I describe my position with regards to personal identity over time. I describe the limits of acceptable psychological change, and discuss which elements of the psyche are essential to our survival.
The Psychological Continuity Criterion
Sydney Shoemaker suggested the theory of psychological continuity as an improvement upon memory continuity (Shoemaker, p. 43). While losing our memories would certainly be a huge loss, it could be possible for people to maintain the same psychological life despite this. But what do we mean when we speak of psychological life? This encompasses more than just memories, including beliefs, passions, and tendencies. Clearly, our mentality changes greatly during the course of our lifetime. This theory, then, allows for a similar transition as Locke’s memory criterion. Although I may no longer be psychologically connected to myself when I was younger, I am certainly still psychologically continuous with her. This is sufficient for me to claim that I have not lost my personal identity.
Improvements upon the memory criterion
By appealing to psychology in general, rather than just memories, we are able to avoid the problems posed in the previous chapter of people suffering memory and, therefore, identity loss. People who suffer amnesia frequently demonstrate the same styles of thought as they had shown prior to the incident, which shows a continuity of self which goes beyond mere memories.
So what happens if one undergoes a complete psychological change? These are extraordinarily rare as, even if one’s entire personality changes, their memories usually remain. For example, someone who has lived a life of terrible sin may experience a religious conversion and change almost every aspect of his life completely willingly. While this is a very extreme change, he will still have memories of his previous life, which provide an adequate link to ensure the continuity of his identity. If he had no memories of his past, we would intuitively agree that there is insufficient continuity between himself now and himself then for them to be the same person.
Schechtman’s concept of empathic access
Marya Schechtman claims that if people change their beliefs, they can only claim to still be the same person if they empathic access to their old beliefs. This does not simply entail having a good memory of those beliefs, but being able to recall them with the same passion as when they were fervently held. Schechtman states that they must look upon their old beliefs favourably and still give them some weight in the decisions they make today. However, many people dismiss their old beliefs and do not wish to give them any weight at all, because they no longer see these old beliefs as relevant to their current decisions. Schechtman gives the example of a party girl who mellows after becoming a mother, to the point that she views her younger days with embarrassment and even disdain. According to Schechtman, this woman is not the same person as she was as a teenager (Schechtman, pp. 102 – 107).
Criticisms of Schechtman’s position
But maturity, and the changes in belief which come with it, are inevitable and should be viewed as a development of our identity rather than a loss of it. For example, children tend to have a very self-centred approach to life and only behave in their own interests. Yet as they mature they gain a greater understanding of manners and courtesy, and are able to put others before themselves when necessary. If we must give weight to our old opinions, as Schechtman claims, we must all give the selfish child within us an opportunity to disregard the feelings of others. It seems that giving all our previous beliefs some consideration results in us giving weight to a lot of contradictory views. More importantly, Schechtman’s attempt to keep a link open to our old selves results in us behaving a manner which is untrue to the recent developments in our personal identity.
I, however, believe what is more important is that the changes a person undergoes as they grow older and presumably wiser, are voluntary changes. As long as the changes are not somehow imposed upon the individual, perhaps as a result of brainwashing or conditioning, the changes a person goes through should not cause them to become an entirely new person.
I believe that the Ship of Theseus is an appropriate analogy for the development and changes which occur in one’s identity. The first few years of our lives are spent building an identity. After that, the usual type of development which occurs in our identities is a gradual one, where new knowledge is integrated alongside the knowledge we already had. If, however, we were to dismiss all of our previous passions, dispositions, beliefs and opinions at once, it is difficult to defend the position that we are still the same person as we were before. Even if we rely on the bodily criterion for some form of continuity, if there is no psychological continuity at all it