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Essays on Personal Identity

Personal identity essay topics.

Exploring personal identity can be a deeply reflective and enlightening process. These essay topics allow writers to delve into various aspects of what makes us who we are, from cultural and social influences to personal experiences and inherent traits.

The theme of Personal Identity is of paramount importance as it delves into the essence of what makes us unique individuals. It encompasses a wide array of factors including culture, language, gender, family dynamics, religion, and personal experiences that together shape our sense of self. Exploring personal identity helps in understanding the complex interplay between individual traits and societal influences, fostering a deeper comprehension of oneself and others.

How to Choose Personal Identity Essay Topics

When selecting a topic for a personal identity essay, consider the following factors:

• Reflect on personal experiences that have shaped your identity.
• Think about the cultural, social, and familial influences in your life.
• Choose a topic that you are passionate about and that resonates with you personally.
• Consider the relevance and significance of the topic in your life and in society.
• Ensure the topic provides ample scope for analysis, reflection, and discussion.

Writing essays on Personal Identity is crucial for several reasons:

• It encourages self-reflection and introspection, allowing individuals to explore and articulate their understanding of their own identity.
• It promotes empathy and cultural awareness by examining how diverse backgrounds and experiences contribute to the mosaic of society.
• Essays on this topic can contribute to critical discussions about the role of external factors, such as social media and globalization, in shaping personal identity.
• They offer a platform for discussing pressing issues related to identity, such as gender identity and the impact of mental health, in a nuanced and informed manner.
• Writing about personal identity challenges writers to consider the dynamic and ever-evolving nature of identity in the modern world.

List of Popular Personal Identity Essay Topics 2024

• Exploring the Impact of Culture on Personal Identity Formation
• Uncovering the Layers of Personal Identity
• The Role of Language in Shaping Individual Identity
• Personal Identity in the Digital Age: Social Media and Self-Perception
• Gender Identity: Navigating the Landscape of Self-Discovery
• The Impacts of Racism and Identity in James Baldwin's "Notes of a Native Son"
• The Influence of Family Dynamics on the Development of Personal Identity
• Religion and Spirituality: Their Contribution to Personal Identity
• The Interplay Between Personal Identity and Mental Health
• Personal Growth and Identity: The Journey Through Life Transitions

List of Personal Identity Essay Topics by Category

Cultural and ethnic identity.

• The Impact of Cultural Heritage on Personal Identity
• Exploring Multicultural Identities: Challenges and Benefits
• The Role of Language in Shaping Cultural Identity
• How Immigration Influences Personal and Cultural Identity
• The Intersection of Race and Identity in Modern Society

Social and Familial Identity

• The Influence of Family Traditions on Personal Identity
• Growing Up in a Single-Parent Household: Effects on Identity
• Siblings and Their Role in Shaping Personal Identity
• How Socioeconomic Status Affects Personal Identity Development
• The Impact of Social Media on Personal and Social Identity

Gender and Sexual Identity

• Exploring the Journey of Gender Identity and Expression
• The Role of Society in Shaping Gender Roles and Identity
• Understanding Non-Binary and Gender-Fluid Identities
• The Intersection of Sexual Orientation and Personal Identity
• Challenges Faced by LGBTQ+ Individuals in Asserting Their Identity

Personal Experiences and Identity

• Overcoming Adversity: How Challenges Shape Personal Identity
• The Role of Education in Shaping Personal and Professional Identity
• How Travel and Exposure to Different Cultures Influence Identity
• The Impact of Major Life Events on Personal Identity Development
• Self-Discovery Through Artistic and Creative Expression

Psychological and Philosophical Perspectives

• The Role of Memory in Constructing Personal Identity
• Nature vs. Nurture: Which Has a Greater Impact on Identity?
• Understanding the Concept of the "Self" in Different Philosophies
• The Influence of Childhood Experiences on Adult Identity
• How Personality Traits Contribute to a Sense of Identity

A Reflection on My Personal Identity

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Who Am I and What is My True Identity

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Understanding of The Meaning of Identity

How to improve your relationship with yourself, the importance and role of the social identity in my life, the issue of equality and self identity in james baldwin's "sonny's blues", negative effect of social media on identity in adolescents, components of our identity by tatum, double identity by jeanne wakatsuki houston: a complex exploration, the problem of identity in "sonny’s blues" and 'a raisin in the sun", the influence of parents on my identity, the topic of identity in the movie the return of martin guerre, the concept of identity by john locke, the concept of gender identity from sociological and physiological perspective, the quest for identity in 'the joy luck club' by amy tan, the maze of identity: quinn’s position in "city of glass", the construction of kathy's identity in "never let me go", unwelcomed identities explored by kincaid and anzaldua, identity construction in alison bechdel’s "fun home", "i, lucy snowe:" identity as performance in villette, "identical seeming skins:" identity and the short story in the beggar maid, aadhar card: scope, misuse and compromise.

Personal Identity refers to the unique characteristics, qualities, beliefs, and values that define an individual and differentiate them from others.

The concept of personal identity, explored in philosophy and psychology, has ancient origins. In ancient Greece, Plato proposed an immortal soul, while Aristotle emphasized the mind and memory. Eastern philosophies like Hinduism embrace reincarnation, and Buddhism suggests identity is impermanent. During the Enlightenment, John Locke argued that personal identity is rooted in consciousness and memory, with continuity of experiences shaping one's sense of self.

• Psychological Continuity: This theory, popularized by John Locke, emphasizes the importance of psychological attributes, such as memory, consciousness, and personality traits, in defining personal identity. According to this view, a person's identity is based on the continuity of their mental states and experiences over time.
• Biological Continuity: This theory emphasizes the role of biological factors in personal identity. It posits that an individual's identity is primarily determined by their physical characteristics and genetic makeup. Biological continuity theorists argue that bodily continuity is essential for personal identity.
• Narrative Identity: This theory, influenced by narrative psychology, asserts that personal identity is constructed through the stories we tell about ourselves. Our sense of self is shaped by the narratives we create to make sense of our experiences, relationships, and life events.
• Bundle Theory: This theory, advocated by David Hume, challenges the notion of a unified and continuous self. According to bundle theory, personal identity is a collection of interconnected mental and physical attributes, thoughts, sensations, and experiences. There is no underlying substance that remains constant over time.
• Social Identity: This theory emphasizes the role of social interactions, cultural contexts, and group affiliations in shaping personal identity. It suggests that identity is not solely an individual construct but is influenced by social norms, roles, and relationships.
• According to a study published in the journal Science, researchers found that our sense of personal identity can be influenced by external factors, such as the opinions of others. The study showed that people were more likely to conform to a group's judgment, even if it conflicted with their own initial perceptions.
• Personal identity can be influenced by language. Linguistic relativity theory suggests that the language we speak affects our perception and understanding of the world, including our sense of self. Different languages may have unique ways of expressing personal identity, which can shape how individuals perceive themselves.
• Personal identity can evolve and change over time. This concept, known as identity fluidity, suggests that individuals may experience shifts in their self-perception due to personal growth, new experiences, or changing social and cultural contexts.

Personal identity is an important topic as it helps individuals understand who they are and how they relate to others. It impacts self-esteem, relationships, career choices, and overall happiness. Exploring personal identity can lead to greater self-awareness, acceptance, and personal growth. It also highlights the importance of embracing diversity and respecting the uniqueness of each individual.

1. Shoemaker, D., & Tobia, K. (2019). Personal identity. (https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3198090) 2. Olson, E. (2016). Personal identity. Science fiction and philosophy: From time travel to superintelligence, 69-90. (https://onlinelibrary.wiley.com/doi/abs/10.1002/9781118922590.ch7) 3. Swinburne, R. G. (1973, January). Personal identity. In Proceedings of the Aristotelian Society (Vol. 74, pp. 231-247). Aristotelian Society, Wiley. (https://www.jstor.org/stable/4544858) 4. Glover, J. (1988). I: The philosophy and psychology of personal identity. (https://philpapers.org/rec/GLOITP) 5. Floridi, L. (2011). The informational nature of personal identity. Minds and machines, 21, 549-566. (https://link.springer.com/article/10.1007/s11023-011-9259-6) 6. Schechtman, M. (2005). Personal identity and the past. Philosophy, Psychiatry, & Psychology, 12(1), 9-22. (https://muse.jhu.edu/pub/1/article/186014/summary) 7. Shoemaker, D. W. (2007). Personal identity and practical concerns. Mind, 116(462), 317-357. (https://academic.oup.com/mind/article-abstract/116/462/317/1083800) 8. Garrett, B. (2002). Personal identity and self-consciousness. Routledge. (https://www.taylorfrancis.com/books/mono/10.4324/9780203015667/personal-identity-self-consciousness-brian-garrett) 9. Luckmann, T., & Berger, P. (1964). Social mobility and personal identity. European Journal of Sociology/Archives Européennes de Sociologie, 5(2), 331-344. (https://www.cambridge.org/core/journals/european-journal-of-sociology-archives-europeennes-de-sociologie/article/abs/social-mobility-and-personal-identity/3A597A028214E9C7F6BD6EA77CFBC881) 10. McLean, K. C., & Syed, M. (2015). Personal, master, and alternative narratives: An integrative framework for understanding identity development in context. Human Development, 58(6), 318-349. (https://www.karger.com/Article/Abstract/445817)

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Personal Identity

Personal identity deals with questions that arise about ourselves by virtue of our being people (or, as lawyers and philosophers like to say, persons ). Many of these questions are familiar ones that occur to everyone at some time: What am I? When did I begin? What will happen to me when I die? Others are more abstruse. Personal identity been discussed since the origins of Western philosophy, and most major figures have had something to say about it. (There is also a rich literature on the topic in Eastern philosophy, which I am not competent to discuss. Collins 1982 and Jinpa 2002 are useful sources.)

I will first survey the main questions of personal identity. Most of the entry will then focus on the one that has received most attention in recent times: our identity over time. I will discuss what the question means, and the main proposed answers. I will also say a bit about how these answers relate to some of the other questions of personal identity, and to more general questions in metaphysics and the philosophy of mind.

1. The Problems of Personal Identity

2. understanding the persistence question, 3. accounts of our identity through time, 4. the psychological approach, 6. the too-many-thinkers problem, 7. the somatic approach, 8. wider issues, bibliography, other internet resources, related entries.

There is no single problem of personal identity, but rather a wide range of loosely connected questions:

Who am I? We often speak of one's “personal identity” as what makes one the person one is. Your identity in this sense consists roughly of what makes you unique as an individual and different from others. Or it is the way you see or define yourself, or the network of values and convictions that structure your life. This individual identity is a property (or set of properties). Presumably it is one you have only contingently—you might have had a different identity from the one you in fact have—and one that you might have for a while and then lose: you could acquire a new individual identity, or perhaps even get by without one. (Ludwig 1997 is a typical discussion.)

Personhood. What is it to be a person? What is necessary, and what suffices, for something to count as a person, as opposed to a non-person? What have people got that non-people haven't got? This amounts more or less to asking for the definition of the word person . An answer would take the form “Necessarily, x is a person if and only if … x …”, with the blanks appropriately filled in. More specifically, we can ask at what point in one's development from a fertilized egg there comes to be a person, or what it would take for a chimpanzee or a Martian or an electronic computer to be a person, if they could ever be. (See e.g. Chisholm 1976: 136f., Baker 2000: ch. 3.)

Persistence. What does it take for a person to persist from one time to another—that is, for the same person to exist at different times? What sorts of adventures could you possibly survive, in the broadest sense of the word 'possible'? What sort of event would necessarily bring your existence to an end? What determines which past or future being is you? Suppose you point to a child in an old class photograph and say, “That's me.” What makes you that one, rather than one of the others? What is it about the way she relates then to you as you are now that makes her you? For that matter, what makes it the case that anyone at all who existed back then is you? This is the question of personal identity over time. An answer to it is an account of our persistence conditions, or a criterion of personal identity over time (a constitutive rather than an evidential criterion: the second falls under the Evidence Question below).

Historically this question often arises out of the hope (or fear) that we might continue to exist after we die—Plato's Phaedo , is a famous example. Whether this could happen depends on whether biological death necessarily brings one's existence to an end. Imagine that after your death there really will be someone, in the next world or in this one, who resembles you in certain ways. How would that being have to relate to you as you are now in order to be you, rather than someone else? What would the Higher Powers have to do to keep you in existence after your death? Or is there anything they could do? The answer to these questions depends on the answer to the Persistence Question.

Evidence. How do we find out who is who? What evidence bears on the question of whether the person here now is the one who was here yesterday? What ought we to do when different kinds of evidence support opposing verdicts? One source of evidence is first-person memory: if you remember doing something, or at least seem to remember, it was probably you who did it. Another source is physical continuity: if the person who did it looks just like you, or even better if she is in some sense physically or spatio-temporally continuous with you, that is reason to think she is you. Which of these sources is more fundamental? Does first-person memory count as evidence all by itself, for instance, or only insofar as we can check it against publicly available physical evidence?

The Evidence Question dominated the philosophical literature on personal identity from the 1950s to the 1970s (Shoemaker 1963 and Penelhum 1970 are good examples). Though it is sometimes confused with the Persistence Question, however, the two are different. What it takes for you to persist through time is one thing; how we might find out whether you have is another. If the criminal had fingerprints just like yours, the courts may conclude that he is you. But even if that is conclusive evidence, having your fingerprints is not what it is for a past or future being to be you: it is neither necessary (you could survive without any fingers at all) nor sufficient (someone else could have fingerprints just like yours).

Population. If we think of the Persistence Question as asking which of the characters introduced at the beginning of a story have survived to become the ones at the end of it, we can also ask how many are on the stage at any one time. What determines how many of us there are now? If there are some six billion people on the earth at present, what facts—biological, psychological, or what have you—make that the right number? The question is not what causes there to be a certain number of people at a given time, but what there being that number consists in. It is like asking what sort of configuration of pieces amounts to black's winning a game of chess, rather than what sorts of moves lead to its winning.

You may think that the number of people at any given time is simply the number of human organisms there are then (perhaps discounting those in a defective state that don't count as people, and ignoring non-human people, if there are any). But this is disputed. Surgeons sometimes cut the nerve bands connecting one's cerebral hemispheres, resulting in such odd behavior as simultaneously pulling one's trousers up with one hand and pulling them down with the other, and, apparently, some sort of disunity of consciousness. You might think that this gives us two people sharing one organism. (See e.g. Nagel 1971. Puccetti 1973 argues that there are two people within the skin of each normal human being.) Or maybe a human being with split personality could literally be the home of two or more thinking beings (Wilkes 1988: 127f.; see also Olson 2003b).

This is sometimes called the problem of “synchronic identity”, as opposed to the “diachronic identity” of the Persistence Question (and the “counterfactual identity” of the How could I have been? Question below). These terms need careful handling, however. They are apt to give the impression that identity comes in two kinds, synchronic and diachronic: a serious blunder. The truth is simply that are two kinds of situations where we can ask how many people (or other things) there are: synchronic situations involving just one moment and diachronic ones involving a stretch of time.

What am I? What sort of things, metaphysically speaking, are you and I and other human people? What is our basic metaphysical nature? For instance, what are we made of? Are we made up entirely of matter, just as stones are, or partly or wholly of something else? If we are made of matter, what matter is it? (Just the matter that makes up our bodies, or might we be larger or smaller than our bodies?) Where, in other words, do our spatial boundaries lie? More fundamentally, what fixes those boundaries? Are we substances—metaphysically independent beings—or is each of us a state or an aspect of something else, or perhaps some sort of process or event?

One possible answer to this broad question is that we are biological organisms. Surprisingly perhaps, most philosophers reject this. (We will return to it later.) Another is that we are partless immaterial substances (or compound things made up of an immaterial soul and a material body: see Swinburne 1984). Hume suggested that each of us is “a bundle of perceptions” (1978: 252; see also Quinton 1962 and Campbell 2006). A popular view nowadays is that we are material things “constituted by” human animals: you are made of the same matter as a certain animal, but you and the animal are different things because what it takes for you to persist is different (Shoemaker 1984: 112–114 and 1999, Baker 2000). Another is that we are temporal parts of animals (Lewis 1976, Hudson 2001). There is even the paradoxical view that there is nothing that we are: we don't really exist at all (Russell 1985: 50, Wittgenstein 1922: 5.631, Unger 1979). (Olson 2007 discusses these matters at length.)

How could I have been? How different could I have been from the way I actually am? Which of my properties do I have essentially, and which only accidentally or contingently? Could I, for instance, have had different parents? Frank Sinatra and Doris Day might have had children together. Could I have been one of them? Or could they only have had children other than me? Could I have died in the womb before ever becoming conscious? Are there possible worlds just like the actual one except for who is who—where people have “changed places” so that what is in fact your career is mine and vice versa? Whether these are best described as questions about personal identity is debatable. (They are not about whether beings in other worlds are identical with people in the actual world: see van Inwagen 1985.) But they are sometimes discussed in connection with the others.

What matters in identity? What is the practical importance of facts about our identity and persistence? Why should we care about it? Why does it matter ? Imagine that surgeons are going to put your brain into my head, and that neither of us has any choice about this. Will the resulting person—who will presumably think he is you—be responsible for my actions, or for yours? (Or both? Or neither?) Suppose he will be in terrible pain after the operation unless one of us pays a large sum in advance. If we were both entirely selfish, which of us would have a reason to pay?

The answer may seem to turn entirely on whether the resulting person would be you or I. Only you can be responsible for your actions. The only one whose future welfare you cannot rationally ignore is yourself. You have a special, selfish interest in your own future, and no one else's. Identity itself matters. But some deny this. They say that someone else could be responsible for your actions. You could have an entirely selfish reason to care about someone else's well-being for his own sake. I care, or ought rationally to care, about what happens to the man people tomorrow will call Olson not because he is me, but because he is then psychologically continuous with me as I am now (see Section 4), or because he relates to me in some other way that doesn't imply that he and I are one. If someone other than me were psychologically continuous tomorrow with me as I am now, he would have what matters to me, and I ought to transfer my selfish concern to him. Identity itself has no practical importance. (See Shoemaker 1970: 284; Parfit 1971, 1984: 215, 1995; Martin 1998.)

That completes our survey of problems. Though these eight questions are clearly related, it is hard to find any interesting common feature that makes them all questions about personal identity. In any case they are different, and it is important not to run them together.

Let us turn now to the Persistence Question. Few concepts have been the source of more misunderstanding than identity over time. The Persistence Question is often confused with other questions, or stated in a tendentious way. It is important to get it right.

The question is what is necessary and sufficient for a past or future being to be you. If we point to you now, and then describe someone or something existing at another time, we can ask whether we are referring to one thing twice, or referring once to each of two things. (There are precisely analogous questions about the persistence of other objects, such as dogs.) The Persistence Question asks what determines the answer to such questions, or makes possible answers true or false.

The question is about numerical identity . To say that this and that are numerically identical is to say that they are one and the same: one thing rather than two. This is different from qualitative identity . Things are qualitatively identical when they are exactly similar. Identical twins may be qualitatively identical—there may be no telling them apart—but not numerically identical, as there are two of them: that's what makes them twins. A past or future person needn't, at that past or future time, be exactly like you are now in order to be you—that is, in order to be numerically identical with you. You don't remain qualitatively the same throughout your life. You change: in size, appearance, and in many other ways. So the question is not what it takes for a past or future being to be qualitatively just like you, but what it takes for a past or future being to be you , as opposed to someone or something other than you.

(Someone might say, as Hume apparently did, that a past or future being couldn't be you unless he or she were then qualitatively just like you are now. That would be a highly contentious metaphysical claim. It amounts to denying that anything can survive any change whatever: even blinking your eyes would be fatal, resulting in your ceasing to exist and being replaced with someone else. It would mean that you did not exist even a moment ago. There would be no point in asking the persistence question if this were the case. Virtually all discussions of personal identity over time assume that it is possible for a person to change.)

The confusion of qualitative with numerical identity is one source of misunderstanding about the Persistence Question. Here is another. People sometimes ask what it takes for someone to remain the same person from one time to another. The idea is that if I were to alter in certain ways—if I lost most of my memory, or my personality changed dramatically, or I underwent a profound religious conversion, say—then I should no longer be the person I was before.

The question of what it takes for someone to remain the same person is not the Persistence Question. It is not even a question about numerical identity. If it were, it would answer itself: I necessarily remain numerically the same for as long as I exist. Nothing could make me a numerically different person from the one I am now. Nothing can start out as one thing and end up as another thing—a numerically different one. This has nothing to do with personal identity in particular, but is simply a fact about the logic of identity.

Those who say that after a certain sort of adventure you would be a different person, or that you would no longer be the person you once were, presumably mean that you would still exist, but would have changed in some important way. If the person resulting from the adventure were not numerically identical with you, it would not be the case that you were “a different person”. Rather, you would have ceased to exist and been replaced by someone else. Those who say these things are usually thinking of one's individual identity in the Who am I? sense: they are talking about the possibility of your losing some or all of the properties that make up your individual identity, and acquiring new ones . This has nothing to do with the Persistence Question.

It is inconvenient that the words ‘identity’ and ‘same’ mean so many different things: numerical identity, qualitative identity, individual psychological identity, and more. To make matters worse, some philosophers speak of “surviving” in a way that doesn't imply numerical identity, so that I could survive a certain adventure without existing afterwards (Parfit 1971). Confusion is inevitable.

Here is a more insidious misunderstanding. Many people try to state the Persistence Question like this:

• Under what possible circumstances is a person existing at one time identical with a person existing at another time?

In other words, what does it take for past or future person to be you? We have a person existing at one time, and a person existing at another, and the question is what is necessary and sufficient for them to be one person rather than two.

This is not the Persistence Question. It is too narrow. We may want to know whether you were ever an embryo or a foetus, or whether you could survive in a persistent vegetative state. These are clearly questions about what it takes for us to persist, and an account of our identity over time ought to answer them. (Their answers may have important ethical implications: it matters to the morality of abortion, for instance, whether something that is an embryo or foetus at one time can be an adult person at another time, or whether the adult person is always numerically different from the foetus.) But many philosophers define ‘person’ as something that has certain mental features. Locke, for instance, famously said that a person is “a thinking intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing, in different times and places” (1975: 335). And neurologists say that early-term foetuses and human beings in a persistent vegetative state have no mental features at all. If anything like Locke's definition is right, such beings are not people. In that case we cannot learn anything about whether you were once an embryo or could come to be a vegetable by discovering what it takes for a past or future person to be you.

We can illustrate the point by considering a particular answer to question 1:

Necessarily, a person who exists at one time is identical with a person who exists at a second time if and only if the first person can, at the first time, remember an experience the second person has at the second time, or vice versa.

That is, a past or future person is you just in the case that you can now remember an experience she had then, or she can then remember an experience you are having now. (This view is also sometimes attributed to Locke, though it is doubtful whether he actually held it.) Call it the Memory Criterion .

The Memory Criterion may seem to imply that if you were to lapse into a persistent vegetative state, the resulting vegetable would not be you, as it would be unable to remember anything: you would have ceased to exist, or perhaps passed on to the next world. But in fact it implies no such thing. Assuming that a human vegetable is not a person, this is not a case involving a person existing at one time and a person existing at another time. The Memory Criterion tells us which past or future person you are, but not which past or future thing : it says what it takes for one to persist as a person , but not what it takes for one to persist without qualification. So it implies nothing at all about whether you could persist as a vegetable. For the same reason it tells us nothing about whether you were ever an embryo. (Olson 1997: 22–26, Mackie 1999: 224–228).

So rather than question 1, we ought to ask what it takes for any past or future being, person or not, to be you or I:

• Under what possible circumstances is a person who exists at one time identical with something that exists at another time (whether or not it is a person then)?

This is the Persistence Question as I understand it. Philosophers typically ask 1 rather than 2 because they assume that every person is a person essentially : nothing that is in fact a person could possibly exist without being a person. (By contrast, something that is in fact a student could exist without being a student: no student is essentially a student.) This claim, “person essentialism”, implies that whatever is a person at one time must be a person at every time when she exists, making the two questions equivalent. Whether it is true, however, is a serious question (an instance of the How could I have been? Question). Person essentialism implies that you could not possibly have been an embryo (given that an embryo is not a person): the embryo that gave rise to you is not strictly you; you came into being only when it developed certain mental capacities. Nor could you come to be a human vegetable. For that matter, it rules out our being biological organisms, since no organism is a person essentially: every human organism starts out as an unthinking embryo, and may end up in a vegetative state.

Whether we are organisms, or were once embryos, are substantive questions that an account of personal identity ought to answer, not matters to be settled in advance by the way we frame the debate. So we cannot assume at the outset that we are people (in something like Locke's sense) essentially. Asking question 1 prejudges the issue by favoring some accounts of what we are, and what it takes for us to persist, over others. In particular, asking 1 effectively rules out the Somatic Approach described in the next section. It is like asking which man committed the crime before ruling out the possibility that it might have been a woman.

Almost all proposed answers to the Persistence Question fall into one of three categories. The first is the Psychological Approach , according to which some psychological relation is necessary or sufficient (or both) for one to persist. You are that future being that in some sense inherits its mental features—beliefs, memories, preferences, the capacity for rational thought, that sort of thing—from you; and you are that past being whose mental features you have inherited in this way. There is dispute over what sort of inheritance this has to be—whether it must be underpinned by some kind of physical continuity, for instance, or whether a “non-branching” requirement is needed. There is also disagreement about what mental features need to be inherited. (I will return to some of these issues.) But most philosophers writing on personal identity since the early 20th century have endorsed some version of the Psychological Approach. The Memory Criterion mentioned earlier is an example. Advocates of the Psychological Approach include Johnston (1987), Garrett (1998), Hudson (2001), Lewis (1976), Nagel (1986, 40), Noonan (2003), Nozick (1981), Parfit (1971; 1984, 207), Perry (1972), Shoemaker (1970; 1984, 90; 1997; 1999), and Unger (1990, ch. 5; 2000).

A second idea is that our identity through time consists in some brute physical relation. You are that past or future being that has your body, or that is the same biological organism as you are, or the like. Whether you survive or perish has nothing to do with psychological facts. I will call this the Somatic Approach . (It should not be confused with the view that physical evidence has some sort of priority over psychological evidence in finding out who is who. That has to do with the Evidence Question.) Its advocates include Ayers (1990: 278–292), Carter (1989), Mackie (1999), Olson (1997), van Inwagen (1990), and Williams (1956–7, 1970).

You may think the truth lies somewhere between the two: we need both mental and physical continuity to survive; or perhaps either would suffice without the other. Views of this sort are usually versions of the Psychological Approach as I have defined it. Here is a test case. Imagine that your brain is transplanted into my head. Two beings result: the person who ends up with your cerebrum and most of your mental features, and the empty-headed being left behind, which may perhaps be biologically alive but will have no mental features. Those who say that you would be the one who gets your brain usually say so because they believe that some relation involving psychology suffices for you to persist: they accept the Psychological Approach. Those who say that you would be the empty-headed vegetable say so because they take your identity to consist in something non-psychological, as the Somatic Approach has it.

Both the Psychological and Somatic Approaches agree that there is something that it takes for us to persist—that our identity through time consists in or necessarily follows from something other than itself. A third view, Anticriterialism , denies this. Mental and physical continuity are evidence for identity, it says, but do not always guarantee it, and may not be required. No sort of continuity is both necessary and sufficient for you to survive. The only correct and complete answer to the Persistence Question is the trivial statement that a person existing at one time is identical with a being existing at another if and only they are identical (Chisholm 1976: 108ff., Swinburne 1984, Lowe 1996: 41ff., Merricks 1998; see also Zimmerman 1998). This is often combined with the view that we are immaterial or have no parts, though it needn't be. Anticriterialism is poorly understood, and deserves more attention than it has received.

It seems that the Persistence Question must have an answer. One of these three views, or another that I haven't mentioned, must be true. If there is such a thing as you—if there is anything sitting there and reading this now—then some conditions must be necessary and sufficient for it to persist. Those conditions will involve psychology, or only brute physical continuity, or something else—or they are trivial, as Anticriterialism has it. Moreover, at most one such view can be true. We will revisit this claim in Section 8, however.

Most people (most Western philosophy teachers and students, anyway) feel immediately drawn to the Psychological Approach. It seems obvious that you would go along with your brain if it were transplanted, and that this is so because that organ would carry with it your memories and other mental features. This would lead the recipient to believe that he or she was you. Why should this belief be mistaken? That suggests that our identity over time has something to do with psychology. It is notoriously difficult, however, to get from this conviction to a plausible answer to the Persistence Question.

What psychological relation might our identity through time consist in? We have already mentioned memory: a past or future being might be you if and only if you can now remember an experience she had then, or vice versa. This faces two famous objections, discovered in the 18th century by Seargeant and Berkeley (see Behan 1979), but more famously discussed by Reid and Butler (see the snippets in Perry 1975).

First, suppose a young student is fined for overdue library books. Later, as a middle-aged lawyer, she remembers paying the fine. Later still, in her dotage, she remembers her law career, but has entirely forgotten paying the fine, and everything else she did in her youth. According to the Memory Criterion, the young student is the middle-aged lawyer, the lawyer is the old woman, but the old woman is not the young student. This is an impossible result: if x and y are one and y and z are one, x and z cannot be two . Identity is transitive; memory continuity is not.

Second, it seems to belong to the very idea of remembering that you can remember only your own experiences. To remember paying a fine (or the experience of paying) is to remember yourself paying. That makes it trivial and uninformative to say that you are the person whose experiences you can remember—that is, that memory continuity is sufficient for personal identity. It is uninformative because you can't know whether someone genuinely remembers a past experience without already knowing whether he is the one who had it. Suppose we want to know whether Blott, who exists now, is the same as Clott, whom we know to have existed at some time in the past. The Memory Criterion tells us that Blott is Clott if Blott can now remember an experience of Clott's that occurred at that past time. But Blott's seeming to remember one of Clott's experiences from that time counts as genuine memory only if Blott actually is Clott. We should have to know who was who before applying the theory that is supposed to tell us who is who. Saying that you are the person whose experiences you can remember is like saying that you are the person who is entitled to your passport: true, but trivial. (Note, however, that this is no objection to the claim that memory connections are necessary for us to persist. There is nothing trivial about that.)

One response to the first problem is to modify the Memory Criterion by switching from direct to indirect memory connections: the old woman is the young student because she can recall experiences the lawyer had at a time when the lawyer remembered the student's life. The second problem is traditionally met by replacing memory with a new concept, “retrocognition” or “quasi-memory”, which is just like memory but without the identity requirement: even if it is self-contradictory to say that I remember doing something I didn't do, I could still “quasi-remember” it (Penelhum 1970: 85ff., Shoemaker 1970; for criticism see McDowell 1997). Neither move gets us far, however, as even the modified Memory Criterion faces a more obvious problem: there are many times in my past that I can't remember or quasi-remember at all, and to which I am not linked even indirectly by an overlapping chain of memories. For instance, there is no time when I could recall anything that happened to me while I was dreamlessly sleeping last night. The Memory Criterion has the absurd implication that I have never existed at any time when I was completely unconscious. The man sleeping in my bed last night was someone else.

A better solution appeals to causal dependence (Shoemaker 1984, 89ff.). We can define two notions, psychological connectedness and psychological continuity. A being is psychologically connected , at some future time, with me as I am now just if he is in the psychological states he is in then in large part because of the psychological states I am in now. Having a current memory (or quasi-memory) of an earlier experience is one sort of psychological connection—the experience causes the memory of it—but there are others. Importantly, one's current mental states can be caused in part by mental states one was in at a times when one was unconscious: for example, most of my current beliefs are the same ones I had while I slept last night. We can then define the second notion thus: I am now psychologically continuous with a past or future being just if my current mental states relate to those he is in then by a chain of psychological connections.

This enables us to avoid the most obvious objections to the Memory Criterion by saying that a person who exists at one time is identical with something existing at another time if and only if the first is, at the first time, psychologically continuous with the second as she is at the second time.

Though this is an improvement, it still leaves important questions unanswered. Suppose we could somehow copy all the mental contents of your brain onto mine, much as we can copy the contents of one computer drive onto another. And suppose this process erased the previous contents of both brains. Whether this would be a case of psychological continuity depends on what sort of causal dependence counts. The resulting being (with my brain and your mental contents) would be mentally like you were before, and not like I was. He would have inherited your mental properties in a way—but a funny way. Is it the right way? Could you literally move from one human animal to another via “brain-state transfer”? Advocates of the Psychological Approach disagree (Shoemaker 1984: 108–111 and 1997, Unger 1990: 67–71). (Schechtman 1996 gives an interesting objection to the psychological-continuity strategy, without abandoning the Psychological Approach.)

Whatever psychological continuity amounts to, a more serious worry for the Psychological Approach is that you could be psychologically continuous with two past or future people at once. If your cerebrum (the upper part of the brain largely responsible for mental features) were transplanted, the recipient would be psychologically continuous with you by anyone's lights (even if there would also be important psychological differences). The Psychological Approach implies that she would be you. If we destroyed one of your cerebral hemispheres, the resulting being would also be psychologically continuous with you. (Hemispherectomy—even the removal of the left hemisphere, which controls speech—is considered a drastic but acceptable treatment for otherwise-inoperable brain tumors: see Rigterink 1980.) What if we did both at once, destroying one hemisphere and transplanting the other? Then too, the one who got the transplanted hemisphere would be psychologically continuous with you, and according to the Psychological Approach would be you.

Now let both hemispheres be transplanted, each into a different empty head. (We needn't pretend, as some authors do, that the hemispheres are exactly alike.) The two recipients—call them Lefty and Righty—will each be psychologically continuous with you. The Psychological Approach as I have stated it implies that any future being who is psychologically continuous with you must be you. It follows that you are Lefty and also that you are Righty. But that cannot be: Lefty and Righty are two, and one thing cannot be numerically identical with two things. Suppose Lefty is hungry at a time when Righty isn't. If you are Lefty, you are hungry at that time. If you are Righty, you aren't. If you are Lefty and Righty, you are both hungry and not hungry at once: a contradiction.

Friends of the Psychological Approach have proposed two different solutions to this problem. One, sometimes called the “multiple-occupancy view”, says that if there is fission in your future, then there are, so to speak, two of you even now. What we think of as you is really two people, who are now exactly similar and located in the same place, doing the same things and thinking the same thoughts. The surgeons merely separate them (Lewis 1976, Noonan 2003: 139–42; Perry 1972 offers a more complex variant).

The multiple-occupancy view is almost invariably combined with the general metaphysical claim that people and other persisting things are made up of temporal parts (often called “four-dimensionalism”; see Heller 1990: ch. 1, Sider 2001). For each person, there is such a thing as her first half, which is just like the person only briefer, like the first half of a race or a football match. On this account, the multiple-occupancy view is that Lefty and Righty coincide before the operation by sharing their pre-operative temporal parts, and diverge later by having different temporal parts located afterwards. They are like two roads that coincide for a stretch and then fork, sharing some of their spatial parts but not others. At the places where the roads overlap, they will look just like one road. Likewise, the idea goes, at the times before the operation when Lefty and Righty share their temporal parts, they will look just like one person—even to themselves. Whether people really are made up of temporal parts, however, is a disputed metaphysical question (see section 8).

The other solution to the fission problem abandons the intuitive claim that psychological continuity by itself suffices for one to persist. It says, rather, that you are identical with a past or future being only if she is then psychologically continuous with you and no other being is. (There is no circularity in this. We need not know the answer to the Persistence Question in order to know how many people there are at any one time; that comes under the Population Question.) This means that neither Lefty nor Righty is you. They both come into existence when your cerebrum is divided. If both your cerebral hemispheres are transplanted, you cease to exist—though you would survive if only one were transplanted and the other destroyed. (Shoemaker 1984: 85, Unger 1990: 265, Garrett 1998: ch. 4; see also Noonan 2003: 12–15 and ch. 7).

This proposal, the “non-branching view”, has the surprising consequence that if your brain is divided, you will survive if only one half is preserved, but you will die if both halves are. That is just the opposite of what most of us expect: if your survival depends on the functioning of your brain (because that is what underlies psychological continuity), then the more of that organ we preserve, the greater ought to be your chance of surviving. In fact, the non-branching view implies you would perish if one of your hemispheres were transplanted and the other left in place: you can survive hemispherectomy only if the excised hemisphere is immediately destroyed. And if “brain-state transfer” gives us psychological continuity, you would cease to exist even if your total brain state were copied onto another brain without erasing yours. (“Best-candidate” theories such as Nozick 1981 attempt to avoid this.)

The non-branching view makes the What matters? Question especially acute. Faced with the prospect of having one of your hemispheres transplanted, there would seem to be no reason to prefer that the other be destroyed. Most of us would rather have both preserved, even if they go into different heads. Yet on the non-branching view that is to prefer death over continued existence. This leads Parfit and others to say that that is precisely what we ought to prefer. Insofar as we are rational, we don't want to continue existing. Or at least we don't want it for its own sake. I only want there to be someone in the future who is psychologically continuous with me, whether or not he is me . Likewise, even the most selfish person has a reason to care about the welfare of the beings who would result from her undergoing fission, even if, as the non-branching view implies, neither would be her. In the fission case, the sorts of practical concerns you ordinarily have for yourself seem to apply to someone who isn't strictly you. This suggests more generally that facts about who is numerically identical with whom have no practical importance. What matters practically is, rather, who is psychologically continuous with whom. (Lewis 1976 and Parfit 1976 debate whether the multiple-occupancy view can preserve the conviction that identity is what matters practically.)

This threatens to undermine the principal argument for the Psychological Approach. Suppose you would care about the welfare of your two fission offshoots in just the way you ordinarily care about your own welfare, even though neither offshoot would be you. Then you would care about what happened to the person who got your whole brain in the original transplant case, even if she would not be you. Even if you would regard that person as yourself for all practical purposes—if you would anticipate her experiences just as you anticipate yours, for instance—that would in no way support the claim that she was you. So our reactions to the brain-transplant case may not support the view that we persist by virtue of psychological continuity, but only the claim that psychological continuity is what matters practically, which is compatible with other accounts of our persistence. In that case we may wonder whether we have any reason to accept the Psychological Approach.

It is sometimes said that fission is not a special problem for the Psychological Approach, but afflicts all answers to the Persistence Question equally, apart (perhaps) from Anticriterialism. Whether this is so is a hard question. Even if it is, though, the fission problem looks especially worrying for the Psychological Approach, as it threatens the support for that view without affecting the arguments for rival views. (It does not undermine arguments for the Somatic Approach, for instance.)

The Psychological Approach faces another problem: it appears to rule out our being organisms (Carter 1989, Ayers 1990: 278–292, Snowdon 1990, Olson 1997: 80f., 100–109, 2003a). It says that our persistence consists in some sort of psychological continuity. As we have seen, this means that you would go along with your transplanted brain or cerebrum, because the one who ended up with that organ, and no one else, would be psychologically continuous with you. Likewise, if you were to lapse into a persistent vegetative state, you would cease to exist, because no one would then be psychologically continuous with you. But the persistence of a human organism does not consist in any sort of psychological continuity. If we transplanted your cerebrum, the human organism—your body—would not go along with that organ. It would stay behind with an empty head. The transplant simply moves an organ from one organism to another. If you were an organism, then you would stay behind with an empty head, contrary to the Psychological Approach. Likewise, no human organism ceases to exist by lapsing into a persistent vegetative state. If you were an organism, you could survive as a human vegetable, which again conflicts with the Psychological Approach. What the Psychological Approach says about our persistence through time is not true of human organisms: no sort of psychological continuity is either necessary or sufficient for a human animal to persist. So if that view is true, we could not be organisms. Not only are we not essentially organisms. We are not organisms at all, even contingently: nothing that is even contingently an organism would go along with its transplanted cerebrum.

But even if you are not an organism, your body is. That organism—a human animal—thinks and is conscious. In fact it would seem to be psychologically indistinguishable from you. So if you are not that animal, but something else, it follows that there is a conscious, intelligent being other than you, now sitting in your chair and reading this article. This means that there are at least twice as many thinking, conscious beings as the census reports: for each of us, there is another thinker, namely the animal we call one's body. Worse, you ought to wonder which of the two thinkers is you. You may believe that you are the non–animal (because you accept the Psychological Approach, perhaps). But the animal has the same grounds for believing that it is a non–animal as you have for supposing that you are. Yet it is mistaken. For all you know, you might be the one making this mistake. If you were the animal and not the person, you would never be any the wiser.

Here is an analogy. Imagine a three-dimensional duplicating machine. When you step into the “in” box, it reads off your information and assembles a perfect duplicate of you in the “out” box. The process causes temporary unconsciousness, but is otherwise harmless. Two beings wake up, one in each box. The boxes are indistinguishable. Because each being will have the same apparent memories and perceive identical surroundings, each will think that he or she is you, and will have the same evidence for this belief. But only one will be right. If this actually happened to you, it is hard to see how you could ever know, afterwards, whether you were the original or the duplicate. (Suppose the technicians who work the machine are sworn to secrecy and immune to bribes.) You would think, “Who am I? Am I who I think I am? Did I do the things I seem to remember doing? Or did I come into being only a moment ago, complete with false memories of someone else's life?” And you would have no way of answering these questions.

In the same way, the Psychological Approach raises the questions, “What am I? Am I a human person, who persists by virtue of psychological continuity? Or am I an animal?” And here too there seem to be no grounds on which to answer these questions. So even if the Psychological Approach is true, it seems that you could never know whether it applied to you: for all you can tell, you may instead be an organism with brute physical persistence conditions. This is the “too-many-minds” or too-many-thinkers problem. It afflicts any view according to which we are not organisms. Only the view that we are organisms (and that there are no beings who persist by virtue of psychological continuity) appears to escape it; but that is incompatible with the Psychological Approach.

Friends of the Psychological Approach can respond in three ways. One is to say that human animals have psychological persistence conditions. (This may be the view of Wiggins 1980: 160, 180 and McDowell 1997: 237; see also Olson 1997: 114–119). Despite appearances, the Psychological Approach is compatible with our being animals, and the problem does not arise. The surgeons do not move your cerebrum from one animal to another in the transplant story. Rather, one animal has its parts cut away until it is the size of a cerebrum. It is then moved across the room and given a new complement of parts. The animal into which your cerebrum is implanted then presumably ceases to exist. This view has not proved popular, however.

A second response is to deny that human animals can think in the way that we do. Although our animal bodies share our brains, are physically just like us, and show all the outward signs of consciousness and intelligence, they themselves do not think and are not conscious. Thinking animals are not a problem for the Psychological Approach because there are none.

If human organisms cannot be conscious, then presumably no biological organism of any sort could have any mental properties at all. Why not? It may be, as Descartes and Leibniz argued, because organisms are material things. If any material thing could think, surely it be an animal! Only an immaterial thing could think or be conscious. You and I must therefore be immaterial. This would solve the too-many-thinkers problem, though it raises many others, and few philosophers nowadays accept it.

Shoemaker attempts to explain why organisms should be unable to think that is compatible with our being material. He says that whatever thinks or is conscious must persist by virtue of psychological continuity. That is because it belongs to the nature of a mental state that it tend to have certain characteristic causes and effects in the being that is in the state, and not in any other being. (This is a version of the functionalist theory of mind.) For instance, your preference for chocolate over vanilla must tend to cause you, and no one else, to choose chocolate. If an organism were to have such a preference, though, that state might cause another being to choose chocolate, because an organism's cerebrum might be transplanted into another organism. That would violate the proposed account of mental states. So no organism could have a preference; and similar reasoning goes for the mental generally. The persistence conditions of organisms are incompatible with their having mental properties. But a material thing that would go along with its transplanted cerebrum—a being of which the Psychological Approach was true—could have mental states. It would follow that you and I, who obviously have mental states, persist by virtue of psychological continuity, and thus are not organisms. This would both solve the too-many-thinkers problem and show that the Psychological Approach is true. (See Shoemaker 1984: 92–97, 1999, 2004, Olson 2002b.)

Finally, friends of the Psychological Approach can concede that human organisms think as we do, so that you are one of two beings now thinking your thoughts, but try to explain how we can still know that we are not those organisms. One strategy for doing this focuses on the nature of personhood and first-person reference. It proposes that not just any being with mental properties of the sort that you and I have—rationality and self-consciousness, for instance—counts as a person. A person must also persist by virtue of psychological continuity. It follows from this that human animals, despite being psychologically just like from us, are not people. Further, personal pronouns such as 'I' refer only to people. So when your animal body says or thinks 'I', it does not refer to itself. Rather, it refers to you, the person who says it at the same time. When the animal says 'I am a person', it does not thereby express the false belief that it is a person, but rather the true belief that you are. It follows that the animal is not mistaken about which thing it is: it has no first-person beliefs about itself at all. And you are not mistaken either. You can infer that you are a person from the linguistic facts that you are whatever you refer to when you say 'I', and that 'I' never refers to anything but a person. You can know that you are not the animal thinking your thoughts because it is not a person, and personal pronouns never refer to non–people.

Although this proposal avoids the surprising claim that organisms cannot have mental properties, however, it gives a highly counterintuitive view of what it is to be a person. And it still implies that there are twice as many intelligent, conscious beings as we thought. (See Noonan 1998, Olson 2002a.)

There appears to be a thinking animal located where you are. It also appears that you are the thinking thing—the only one—located there. If things are as they appear, then you are that animal. This view has become known as Animalism .

Animalism does not imply that all animals, or even all human animals, are people: as we saw earlier, human embryos and animals in a persistent vegetative state may not count as people. Being a person may be only a temporary property of you, like being a philosopher. Nor does animalism imply that all people are animals. It is consistent with the existence of wholly inorganic people: gods or angels or conscious robots. It does not say that being an animal is part of what it is to be a person (a view defended in Wiggins 1980, 171 and Wollheim 1984, ch. 1 and criticized in Snowdon 1996). Animalism leaves the answer to the Personhood Question entirely open.

If we are animals, we have the persistence conditions of animals. And as we saw, animals appear to persist by virtue of some sort of brute physical continuity. So Animalism seems to imply a version of the Somatic Approach.

A few philosophers endorse the Somatic Approach without saying that we are animals. They say that we are our bodies (Thomson 1997), or that our identity through time consists in the identity of our bodies (Ayer 1936: 194). This has been called the Bodily Criterion of personal identity. Its relation to Animalism is uncertain. If a person's body is by definition a sort of animal, then perhaps being identical to one's body is the same as being an animal. Whether this is so depends in part on what it is for something to be someone's body—a surprisingly difficult question (see van Inwagen 1980, Olson 1997: 144–149).

We have already seen the most common objection to the Somatic Approach: it implies that you would stay behind if your cerebrum were transplanted, which can seem incredible (see Unger 2000).

That said, the Somatic Approach has the virtue of being compatible with our beliefs about who is who in real life. Every actual case in which we take someone to survive or perish is a case where a human animal survives or perishes. The Psychological Approach, or at any rate the view that psychological continuity is necessary for us to persist, does not share this virtue. When someone lapses into a persistent vegetative state, his friends and relatives rarely conclude that their loved one no longer exists, even when they believe that there is no psychological continuity of any sort between the vegetable and the person. (They may conclude that his life no longer has any value, but that is another matter.) And most of us believe that we were once foetuses. When we see an ultrasound picture of a 12-week-old foetus, we ordinarily think we are seeing something that will, if all goes well, be born, learn to speak, and eventually become an adult human person. Yet none of us is in any way psychologically continuous with a 12-week-old foetus.

Some versions of the Somatic Approach also face their own version of the too-many-thinkers problem. The mere fact that you are an organism or the like does not imply that you are the only thinker of your thoughts (Shoemaker 1999, Hudson 2007, Olson 2007: 215-236). This would of course be no more of a problem for the Somatic than for the Psychological Approach; but it would undermine the best argument for the Somatic Approach, the one based on the too-many-thinkers problem.

We have compared the virtues of the two main accounts of our identity over time. We saw that the Psychological Approach, though attractive, has trouble with fission cases. The usual non–branching response is both implausible in itself and suggests that identity has no practical importance, which in turn undermines the original support for the view. The Psychological Approach also implies that we are not animals, raising the awkward problem of how we relate to the apparently intelligent animals we call our bodies. The Somatic Approach—in particular when combined with the view that we are animals—is also intuitively attractive, and appears to avoid the too-many-thinkers problem. But it has implausible consequences concerning brain transplants.

The debate between these competing views is likely to turn on more general issues in metaphysics and the philosophy of mind. For instance, advocates of the Psychological Approach appear to be committed to the view that each normal human organism is associated with a non-organism that thinks and is conscious. They will need an account of the metaphysical nature of this non-organism, and of how it relates to the animal. If they hope to solve the thinking-animal problem by denying that human animals can think, they will need an account of the nature of the mental that is consistent with this.

Some general metaphysical views suggest that there is no unique right answer to the question of what it takes for us to persist. The best-known example is the ontology of temporal parts mentioned in section 5. It says that for every period of time when you exist, short or long, there is a temporal part of you that exists only then. This gives us many likely candidates for being you or me. Suppose you are a material thing, and that we know what determines your spatial boundaries. That should tell us what counts as your current temporal part or “stage”—the temporal part of you located now and at no other time. That stage is a part of a vast number of temporally extended objects (Hudson 2001: ch. 4). For instance, it is a part of a being whose temporal boundaries are determined by relations of psychological continuity, in the sense defined in Section 4, among its stages. That is, one of the beings thinking your current thoughts is an aggregate of person-stages, each of which is psychologically continuous with each of the others and not with anything else. The view that we persist by virtue of psychological continuity suggests that that is what you are.

Your current stage is also a part of a being whose temporal boundaries are determined by relations of psychological connectedness (Section 4 again). That is, one of the beings now thinking your thoughts is an aggregate of person-stages, each of which is psychologically connected with each of the others and not to anything else. This may not be the same as the first being, for some stages may be psychologically continuous with your current stage but not psychologically connected with it. The view that psychological connectedness is necessary and sufficient for us to persist suggests that we are beings of the second sort (Lewis 1976). Your current stage is also a part of a human animal, which persists by virtue of brute physical continuity. And it is a part of many bizarre and gerrymandered objects, such as Hirsch's “contacti persons” (Hirsch 1982, ch. 10). Some even say that you are your current stage itself (Sider 2001, 188–208).

The temporal-parts ontology implies that each of us shares our current thoughts with countless beings that diverge from one another in the past or future. This makes it hard to say which things we are. And because many of these beings persist through time under different conditions, it is equally hard to say what our identity over time consists in. How could we ever know? Of course, we are the beings we refer to when we say ‘I’, or more generally the beings that our personal pronouns and proper names refer to; but it is unlikely, on this view, that our personal pronouns succeed in referring to just one sort of thing. Each utterance of a personal pronoun will probably refer ambiguously to many different candidates: to various sorts of psychologically interrelated aggregates, to an animal, and perhaps to others as well. That would make it indeterminate which things, even which kind of things, we are. And insofar as the different candidates have different persistence conditions, it would be indeterminate what our identity over time consists in. Some versions of the metaphysic of constitution (Baker 2000) have similar implications.

These wider questions—about the nature of mental properties and the existence of temporal parts, among others—cannot be settled by thinking about personal identity alone. Which view of personal identity we find attractive is likely to depend on general metaphysical considerations. There may not be much point in asking about our identity over time without first addressing these underlying issues.

• Ayer, A. J., 1936, Language, Truth, and Logic , London: Gollancz.
• Ayers, M., 1990, Locke , vol. 2, London: Routledge.
• Baker, L. R., 2000, Persons and Bodies: A Constitution View , Cambridge University Press
• Behan, D., 1979, ‘Locke on persons and personal identity’, Canadian Journal of Philosophy 9: 53–75
• Campbell, S., 2006, 'The Conception of a Person as a Series of Mental Events', Philosophy and Phenomenological Research 73: 339–358
• Carter, W. R., 1989, ‘How to Change Your Mind’, Canadian Journal of Philosophy 19: 1–14
• Chisholm, R., 1976, Person and Object , La Salle, IL: Open Court
• Collins, S., 1982, Selfless Persons: Imagery and Thought in Theravada Buddhism , Cambridge University Press
• Garrett, B., 1998, Personal Identity and Self-Consciousness , London: Routledge
• Heller, M., 1990, The Ontology of Physical Objects: Four-Dimensional Hunks of Matter , Cambridge University Press
• Hirsch, E., 1982, The Concept of Identity , Oxford University Press
• Hudson, H., 2001, A Materialist Metaphysics of the Human Person , Cornell University Press
• –––, 2007, 'I Am Not an Animal!', in Persons: Human and Divine , P. van Inwagen and D. Zimmerman (eds.), Oxford: Clarendon Press
• Hume, D., 1978, Treatise of Human Nature , Oxford: Clarendon Press (original work 1739); partly reprinted in Perry 1975
• Jinpa, T., 2002, Self, Reality and Reason in Tibetan Philosophy , London: RoutledgeCurzon
• Johnston, M., 1987, ‘Human Beings’, Journal of Philosophy 84: 59–83
• Lewis, D., 1976, ‘Survival and Identity’, in The Identities of Persons , A. Rorty (ed.), Berkeley: California, and reprinted in his Philosophical Papers vol. I, Oxford University Press, 1983
• Locke, J., 1975, An Essay Concerning Human Understanding , ed. P. Nidditch, Oxford: Clarendon Press (original work, 2nd ed., first published 1694); partly reprinted in Perry 1975
• Lowe, E. J., 1996, Subjects of Experience , Cambridge University Press
• Ludwig, A. M., 1997, How Do We Know Who We Are? , Oxford University Press
• Mackie, D., 1999, ‘Personal Identity and Dead People’, Philosophical Studies 95: 219–242
• Martin, R., 1998, Self Concern , Cambridge University Press
• Martin, R. and J. Barresi (eds.), 2003, Personal Identity , Oxford: Blackwell.
• McDowell, J., 1997, ‘Reductionism and the First Person’, in Reading Parfit , J. Dancy (ed.), Oxford: Blackwell
• Merricks, T, 1998, ‘There Are No Criteria of Identity Over Time’, Noûs 32: 106–124
• Nagel, T. 1971, ‘Brain Bisection and the Unity of Consciousness’, Synthèse 22: 396–413, and reprinted in Perry 1975 and in Nagel, Mortal Questions , Cambridge University Press 1979
• –––, 1986, The View from Nowhere , Oxford University Press
• Noonan, H., 1998, ‘Animalism Versus Lockeanism: A Current Controversy’, Philosophical Quarterly 48: 302–318
• –––, 2003, Personal Identity , Second Edition, London: Routledge
• Nozick, R, 1981, Philosophical Explanations , Harvard University Press
• Olson, E. 1997. The Human Animal: Personal Identity Without Psychology , Oxford University Press
• –––, 2002a, ‘Thinking Animals and the Reference of “I”’, Philosophical Topics 30: 189–208
• –––, 2002b, ‘What does Functionalism Tell Us about Personal Identity?’, Noûs 36: 682–98
• –––, 2003a, ‘An Argument for Animalism’, in Martin and Barresi 2003
• –––, 2003b, ‘Was Jekyll Hyde?’, Philosophy and Phenomenological Research 66: 328–48
• –––, 2007, What Are We? A Study in Personal Ontology , Oxford University Press
• Parfit, D, 1971, ‘Personal Identity’, Philosophical Review 80: 3–27, and reprinted in Perry 1975
• –––, 1976, ‘Lewis, Perry, and What Matters’, in The Identities of Persons , A. Rorty (ed.), Berkeley: University of California Press
• –––, 1984, Reasons and Persons . Oxford: Oxford University Press
• –––, 1995, ‘The Unimportance of Identity’, in Identity , H. Harris (ed.), Oxford: Oxford University Press. Reprinted in Martin and Barresi 2003.
• Penelhum, T., 1970, Survival and Disembodied Existence , London: Routledge.
• Perry, J., 1972, ‘Can the Self Divide?’ Journal of Philosophy 69: 463–488
• ––– (ed.), 1975, Personal Identity , Berkeley: University of California Press
• Puccetti, R., 1973, ‘Brain Bisection and Personal Identity’, British Journal for the Philosophy of Science 24: 339–355
• Quinton, A., 1962, ‘The Soul’, Journal of Philosophy 59: 393–403, and reprinted in Perry, ed., 1975
• Rea, M., ed., 1997, Material Constitution: A Reader , Lanham, MD: Rowman & Littlefield
• Rigterink, R., 1980, ‘Puccetti and Brain Bisection: An Attempt at Mental Division’, Canadian Journal of Philosophy 10: 429–452
• Russell, B., 1918, ‘The Philosophy of Logical Atomism’. Monist 28: 495–527 and 29: 32–63, 190–222, 345–380; reprinted in R. Marsh, ed., Logic and Knowledge (London: Allen & Unwin, 1956), and in D. Pears, ed., The Philosophy of Logical Atomism (La Salle, IL: Open Court, 1985) [page numbers from the latter]
• Schechtman, M., 1996, The Constitution of Selves , Cornell University Press
• Shoemaker, S., 1963, Self-Knowledge and Self-Identity , Ithaca: Cornell University Press
• –––, 1970, ‘Persons and Their Pasts’, American Philosophical Quarterly 7: 269–285
• –––, 1984, ‘Personal Identity: A Materialist's Account’, in Shoemaker and Swinburne, Personal Identity , Oxford: Blackwell
• –––, 1997, ‘Self and Substance’, in Philosophical Perspectives 11, J. Tomberlin (ed.): 283–319
• –––, 1999, ‘Self, Body, and Coincidence’, Proceedings of the Aristotelian Society , Supplementary Volume 73: 287–306
• –––, 2004, ‘Functionalism and Personal Identity--A Reply’, Noûs 38: 525-33
• Sider, T., 2001, Four Dimensionalism , Oxford University Press
• Snowdon, P., 1990, ‘Persons, Animals, and Ourselves’, in The Person and the Human Mind , C. Gill. (ed.), Oxford: Clarendon Press
• –––,1996, ‘Persons and Personal Identity’, in Essays for David Wiggins: Identity, Truth and Value , S. Lovibond and S. G. Williams (ed.), Oxford: Blackwell
• Swinburne, R., 1984, ‘Personal Identity: The Dualist Theory’, in Shoemaker and Swinburne, Personal Identity , Oxford: Blackwell
• Thomson, J. J., 1997, ‘People and Their Bodies’, in Reading Parfit , J. Dancy (ed.), Oxford: Blackwell
• Unger, P., 1979, ‘I do not Exist’, in Perception and Identity , G. F. MacDonald (ed.), London: Macmillan, and reprinted in Rea 1997
• –––, 1990, Identity, Consciousness, and Value , Oxford University Press
• –––, 2000, ‘The Survival of the Sentient’, in Philosophical Perspectives 11, J. Tomberlin (ed.), Malden, MA: Blackwell
• van Inwagen, P., 1980, ‘Philosophers and the Words “Human Body”’, in Time and Cause , P. van Inwagen (ed.), Dordrecht: Reidel, and reprinted in his Ontology, Identity, and Modality (Cambridge University Press, 2001)
• –––, 1985, ‘Plantinga on Trans-World Identity, in Alvin Plantinga , J. Tomberlin and P. van Inwagen (ed.), Dordrecht: Reidel, and reprinted in his Ontology, Identity, and Modality (Cambridge University Press, 2001)
• –––, 1990, Material Beings , Ithaca: Cornell University Press
• Wiggins, D., 1980, Sameness and Substance , Oxford: Blackwell
• Wilkes, K, 1988, Real People , Oxford: Clarendon Press
• Williams, B, 1956–7, ‘Personal Identity and Individuation’, Proceedings of the Aristotelian Society 57, and reprinted in his Problems of the Self (Cambridge University Press, 1973)
• –––, 1970, ‘The Self and the Future’, Philosophical Review 59, and reprinted in his Problems of the Self (Cambridge University Press, 1973)
• Wittgenstein, L., 1922, Tractatus Logico-Philosophicus , London: Routledge
• Wollheim, R., 1984, The Thread of Life , Cambridge University Press
• Zimmerman, D., 1998, ‘Criteria of Identity and the “Identity Mystics”’, Erkenntnis 48, 281–301
• Persons and Bodies: A Constitution View , symposium on the book by Lynne Rudder Baker, at the website A Field Guide to the Philosophy of Mind , maintained by Marco Nani and Massimo Marraffa (Università degli Studi Roma Tre)
• Symposium on Olson's The Human Animal , in the online journal Abstracta

identity | identity: relative | Locke, John | personal identity: and ethics | temporal parts

Acknowledgments

Some material in this entry appeared previously in E. Olson, ‘Personal Identity’, in The Blackwell Guide to the Philosophy of Mind , edited by S. Stich and T. Warfield, Oxford: Blackwell, 2003.

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In This Article Expand or collapse the "in this article" section John Locke: Identity, Persons, and Personal Identity

Introduction, relevant works by locke.

• Locke’s Account of Identity
• Locke on Substance, Mode, and Body
• Locke on Persons, Moral Agents, Accountability, Action Appropriation, Reward and Punishment
• Locke on Personal Identity, Consciousness, and Memory
• Theological Context
• Common Objections: Circularity, Transitivity, “Fatal Error”
• Responses by Locke’s Contemporaries and Early Critics
• Neo-Lockean Theories and Other Present-Day Approaches

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John Locke: Identity, Persons, and Personal Identity by Ruth Boeker LAST REVIEWED: 25 June 2013 LAST MODIFIED: 25 June 2013 DOI: 10.1093/obo/9780195396577-0056

John Locke offered a very rich and influential account of persons and personal identity in “Of Identity and Diversity,” which is chapter 27 of Book 2 of his An Essay concerning Human Understanding . He added it to the second edition in 1694 upon the recommendation of his friend William Molyneux. Locke’s theory was soon after its publication discussed by his contemporaries and has influenced many present-day discussions of personal identity. Distinctive about Locke’s theory is that he argues that the notion of a person is to be distinguished from that of a human organism, or “man” to use Locke’s term, and that of a substance. By distinguishing the notion of a person from the more traditional notions of a human organism and a substance, Locke is able to address moral questions of accountability without having to take a stance on the question of whether the underlying ontological constitution of a person is material or immaterial. The chapter can be divided into two parts: in the first he outlines his general account of identity, and in the second he applies his general account of identity to persons and personal identity. The discussion of Locke’s general account of identity in the secondary literature has focused on whether Locke’s account of identity can be regarded as a version of the thesis that identity is relative and on how Locke understands modes and substances in chapter 27. The secondary literature on Locke’s account of persons and personal identity often focuses on how Locke’s claim that personal identity consists in sameness of consciousness is to be understood. However, some interpreters also draw attention to the importance of the moral and legal dimension which Locke makes explicit in his claim that “person” is a forensic term (II.xxvii.26). Moreover, some scholars have argued that Locke’s theory is to be understood in its religious context. The objections which have repeatedly been raised against Locke include the problem of circularity and the problem of transitivity; Locke’s reference to “fatal error” in II.xxvii.13 has also been regarded as a serious problem for his view. In the 20th century, psychological accounts of personal identity were often called neo-Lockean theories. It is controversial whether neo-Lockean theories differ from Locke’s own theory, and it can be asked whether the moral and religious dimension of Locke’s theory constitutes an important difference.

The most important source for understanding Locke’s account of identity, persons, and personal identity is Locke 2008 . (References to the Essay are given by Book, chapter, and section; e.g., II.xxvii.9.) Locke offers his account of identity, persons, and personal identity in II.xxvii. Locke’s journal entries from 20 February 1682, reprinted in Locke 1936 and Locke 1683 , document his early thoughts on the topic. Other particularly relevant chapters include “Of Power” (II.xxi), which he revised at the time he wrote II.xxvii; his chapters on modes, substances, and relations (II.xxii–xxiv, xxviii); and his chapter on general terms (III.iii). Among Locke’s other writings, his correspondence with Molyneux ( Locke 1976–1989 , Volumes 4 and 5) provides helpful insight into the composition of II.xxvii. Additionally, some parts of Locke’s correspondence with Edward Stillingfleet help to clarify Locke’s views ( Locke 1824 , Volume 3). Helpful background is further provided by Locke 2002 , Locke 1997 , and Locke 1988 , especially the chapter “Of Property” ( Locke 1988 , II.v).

Locke, John. Identity of Persons . Bodleian Library MS Locke f. 7, 5 June 1683.

Locke’s first note concerning personal identity. Not as fully developed as his later theory, but Locke already rejects the view that personal identity consists in sameness of material particles or “corporeal spirits” and claims that personal identity consists in memory and knowledge of one’s past.

Locke, John. The Works of John Locke . 12th ed. 9 vols. London: Rivington, 1824.

Contains Locke’s major works, including posthumously published writings and letters. Volume 3 presents Locke’s letters to Stillingfleet.

Locke, John. An Early Draft of Locke’s Essay: Together with Excerpts from His Journals . Edited by R. I. Aaron and Jocelyn Gibb. Oxford: Clarendon, 1936.

Contains Draft A of Locke’s Essay , which was written in 1671, and excerpts from Locke’s journals that illuminate Locke’s arguments in the Essay . Locke’s journal entry from 20 February 1682 concerns immortality and provides relevant background to his account of personal identity.

Locke, John. An Essay Concerning Human Understanding . Edited by Peter H. Nidditch. Oxford: Clarendon, 2008.

Critical edition, based on the fourth edition (1700; originally published in 1690, second edition 1694). Best edition for students and scholars. The text is unmodernized and includes Locke’s own index. The chapter “Of Identity and Diversity” (II.xxvii, originally published in 1694) is reprinted in John Perry, ed., Personal Identity (University of California Press, 2008).

Locke, John. Two Treatises of Government . Edited by Peter Laslett. Cambridge, UK: Cambridge University Press, 1988.

DOI: 10.1017/CBO9780511810268

Originally published anonymously in 1690. This edition is prepared for students and contains a detailed introduction, helpful annotations to the text, suggested readings, an extensive bibliography, and an index.

Locke, John. The Correspondence of John Locke . 8 vols. Edited by E. S. De Beer. Oxford: Clarendon, 1976–1989.

Critical edition of Locke’s correspondence. Locke’s correspondence with Molyneux can be found in Volumes 4 and 5 and is reprinted in Mark Goldie, ed., John Locke: Selected Correspondence (Oxford University Press, 2002).

Locke, John. Political Essays . Edited by Mark Goldie. Cambridge, UK: Cambridge University Press, 1997.

A helpful collection which makes easily accessible major and minor essays by Locke focused on political, moral, and religious themes. Locke did not write a systematic work on morality, and the essays included in this collection provide good insight into his thinking on the subject. Contains an introduction, bibliography, and index.

Locke, John. Writings on Religion . Edited by Victor Nuovo. Oxford: Clarendon, 2002.

Offers a good selection of Locke’s writings on religion, prepared for students and scholars. Nuovo’s helpful introduction outlines Locke’s deep interest in religion and theology and suggests that understanding Locke’s works in the context of his religious writings helps one to realize how many of Locke’s works bear upon his religious work.

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Chapter 4: Personal identity

Personal identity

Matthew Van Cleave

Introduction: the persistence question

Imagine a wooden ship called “TS” that was built 100 years ago and that has been in continual use up until today. As time has passed, parts of TS have decayed and have needed to be replaced. Eventually, none of TS’s parts are original; all of them have been replaced. Is TS the same boat as it was 100 years ago? [1] On the one hand, it seems that it cannot be since the physical object has undergone a radical change—it is literally a totally different physical object. One the other hand, we are inclined to still call it “TS” since it has been in continual use since it was first built and it has always been called “TS.” These two answers suggest two very different criteria about the identity conditions of objects. The first answer suggests that an object is the same object only if there is some intrinsic property of the object that stays the same through time (and that if there are no such properties then it follows that it is no longer the same ship as it was at the start). The second answer suggests that an object is the same object as long as it has some extrinsic property that remains such same. Being called the by the same name (or perceived by people to be the same object) over time is a good example of an extrinsic property since it is not something that the object itself contains but, rather, something that is “put onto” the objection from outside. On this criterion, TS is the same ship since people have always called it “TS.”

The question about the identity of the boat represents a very general metaphysical question about the identity of physical objects: what are the criteria by which objects remain numerically identical? Numerical identity is a term that philosophers use to describe an object being the very same object. It is contrasted with qualitative identity which simply means that an object has all the same properties or qualities. An object is only numerically identical to itself but can be qualitatively identical to other objects. For example, imagine two identical red Corvettes. The two red Corvettes are qualitatively identical (since if you closed your eyes could not tell whether one has been substituted for the other), but they are not numerically identical (because they are two different cars). The persistence question of identity is the question about the conditions under which an object remains numerically identical. For example, if the ship were disassembled and the wood used to build a house, it seems clear that it would no longer be the same object (even if its physical material were the same) since it is no longer a boat but a house. Likewise, if the red Corvette were melted down into metal and then fashioned into a boat, it would no longer be the same object.

Although we can ask the persistence question about objects in general, one kind of thing whose identity conditions philosophers have been very interested in is persons. The persistence question of personal identity is the question about the conditions under which a particular human being remains numerically the same. [2] The philosophical problem is that although it seems that that a person remains numerically identical throughout their life, it is very difficult to give a satisfying answer to what accounts for this numerical identity. More specifically, the problem is that although we are inclined to think that there is some intrinsic property that makes a person numerically the same throughout their life, it is very difficult to come up with what this intrinsic property is. Perhaps there is no intrinsic property; perhaps the only thing that makes me me is that others have always called me “Matt Van Cleave.” However, that answer also seems to lack the depth that we think our personal identity has. After all, it seems that there is a clear sense in which I would still be me even if all of a sudden people started calling me by a different name. Suppose I was kidnapped and taken to a different place where no one knew me but where I looked exactly like someone called Todd Quiring. The fact that everyone now calls me “Todd Quiring” doesn’t seem to change who I am in any deep way.

In this chapter we will consider a few different answers to the persistence question. John Locke’s psychological continuity account and Bernard Williams’s bodily continuity account both attempt to find an intrinsic property that grounds our personal identity. In contrast, Daniel Dennett’s short story “Where am I?” raises the question of whether there is any intrinsic property that grounds personal identity. In philosophy, this idea is famously linked to David Hume, but it also connects with the Buddhist concept of anattā (“no self”). Whereas the persistence question is a metaphysical question, in the last part of the chapter we will consider what I call the psychological question of personal identity : Where does my sense that that I am the same person throughout my life come from? Notice that even if it were to turn out that metaphysically there is no self that persists throughout our whole lives, it still makes sense to ask this psychological question about our sense of our identity. That is, even if there is no deep sense in which I am the same person I was 20 years ago, there can still be an account of what gives me the sense that I am (if indeed I have that sense). [3]

Personal identity as an unchanging, intrinsic property

Before considering Locke’s view of personal identity, let’s consider one idea about what kind of thing would answer the persistence question. It is commonly thought our personal identity should consist in some one thing that is unchanging and intrinsic. For example, within certain religious traditions, the idea of an immaterial soul is often seen as the thing that makes us the same person. Although our bodies, our beliefs, and our values may change radically throughout our lifetimes, our soul is thought to stay the same. However, if it is possible for our souls to leave our bodies and inhabit other bodies (such as in reincarnation) then it seems problematic for souls to ground my personal identity. If one soul can inhabit many different persons, then it cannot be the soul that distinguishes one person from another. In addition, positing a soul raises certain kinds of epistemological questions: How do we know that souls exist? Even if souls exist, how do we know they don’t themselves undergo change? How do I know that my soul is the same from one moment to the next? For these reasons and others, philosophers have tended to look elsewhere for an answer the persistence question of personal identity.

Is there some other thing about me that always stays the same? What about my body? Like the example of the ship, my body naturally regenerates all of its physical matter certain number of years (how long depends on which organs/cells we are talking about). Although neurons in our cerebral cortex do not regenerate, the connections between the neurons in our brain are continually changing (this is what happens when learning takes place). In any case, it seems implausible to maintain that some is some particular neuron or set of neurons in the cerebral cortex that account for why I am the same. What about DNA? The DNA within our bodily cells stays largely the same (except when uncorrected errors in replication occur, which is rare). But consider identical twins (which have the same DNA). Clearly identical twins are two different persons. But if DNA were the basis of personal identity, there would be only one person. How about fingerprints—don’t those stay the same throughout my lifetime? Yes, they do—unless I were to lose my hands. But in that case, am I really now a different person? It seems not. The other problem with DNA and fingerprints is that they don’t seem to have much to do with who we are as persons . Many philosophers since Locke have viewed the concept of a person as a forensic concept , meaning a concept that is essentially tied to our notions of moral and legal responsibility. Persons are individuals have have moral and legal rights and can be held responsible for their actions. The problem with DNA and fingerprints is that neither one has much to do with our personhood and agency and for this reason wouldn’t be able to explain much about personal identity. Thus it seems that there is no one physical thing that persists throughout our lifetime that could ground our personal identity. For this reason, philosophical accounts of personal identity have eschewed the idea that there is some one thing that stays same throughout my life. Instead, philosophers have tended to claim that what grounds identity is a kind of continuity between aspects of ourselves at different times.

Personal identity as psychological continuity

John Locke (1632-1704) claimed that I remain the same person through time because I am conscious of being the same person through time and that “as far as this consciousness can be extended backwards to any past action or thought, so far reaches the identity of that person.” [4] Locke’s criterion is commonly interpreted as a memory criterion of personal identity : personal identity consists in one’s ability to remember things about their own past from a first-person perspective. For example, since I can remember things about being 20 years old (or even 10 years old) it follows that I am now numerically identical to the person as I was then. The fact that these memories are from the first-person perspective is crucial. It isn’t just that I can remember certain events taking place (since perhaps some of my friends remember those same events). Rather, it is that I remember those events from my first-person perspective . For Locke, what makes a person the same person must be essentially tied to what persons are and for Locke “person” is a forensic concept , meaning a concept that is essentially tied to the concept of agency and thus to our notions of moral and legal responsibility. Persons are individuals who have moral and legal rights and who can be held responsible for their actions. (For this reason, Locke would reject DNA and fingerprints as grounding personal identity since neither one has much to do with the capacities that underlie our lives as agents.)

The memory criterion has a broad appeal since it seems plausible that much of our sense of ourselves is due to our memories of our past. It does seem that without the ability to remember anything about my past (as in cases of severe amnesia or dissociative fugue states ) I would not be the same person. Furthermore, the memory criterion of personal identity carries with it a criterion for moral responsibility: we cannot be held responsible for things of which we have no memory. The memory criterion is also appealing because it accounts for the commonly held idea that our minds are central to who we are as persons (since memory is a psychological attribute). Finally, since psychological properties are intrinsic properties of persons, Locke’s memory criterion accounts for the commonly held belief that our personal identities are real and deep. So far, so good. However, the memory criterion is not without its problems.

Suppose that Bob commits a heinous murder when he is 25 years old and is never caught for it. 50 years later he is finally apprehended but now Bob has late stage Alzheimer’s disease and cannot remember anything about his earlier life. What would Locke’s memory criterion say about whether Bob should be punished for the earlier murder? The memory criterion implies that Bob is literally not the same person now as he was then. If we assume that it is fair only to punish the person who committed the crime, it would not be fair to punish Bob today since he is a different person (according to the memory criterion). Think of it this way: it is no more fair to punish Bob for the murder than it is to punish his friend Bill, who had nothing to do with the murder. On Locke’s memory criterion, Bob at 75 years old is no more the same person than Bob at 25 years old than his friend Bill is. Neither one has the right kind of memory connection to Bob at 25 years old. In fact, since no existing person has the right kind of memory connection to 25 year old Bob, it follows that there is no existing person that committed the crime (and thus no one can be punished). Locke anticipated this problem and accepts that if Bob truly cannot remember his earlier life, then it is not fair to punish him (since he is not the same person who committed the murder). However, Locke also thinks that we should still punish people who have committed crimes even if they claim they can’t remember it since if we didn’t, then anyone found guilty of a crime could claim they didn’t remember the crime as a way of exculpating themselves. So Locke thinks that we have to hold people accountable. If we were omniscient like god, then we would know when someone really couldn’t remember (and thus wasn’t the same person) and when they were just lying to escape punishment. But since we aren’t, we are stuck with an inferior kind of justice that may sometimes punish those who don’t deserve it.

Another problem that arises for Locke’s memory criterion is what happens when we are in a state in which we cannot remember anything from our earlier lives— for example, when I am unconscious, such as I am when I sleep. Someone who is asleep does not have the ability to remember earlier events in one’s life and thus it seems to follow that when a person is asleep they are not the same person as when they are awake. Indeed, if personhood requires the ability to remember at all, then it seems that the unconscious person is not really a person at all. But this seems all wrong. It does not seem that when I am sleeping I cease to be numerically identical to the person I am when I am awake. One way of trying to solve this problem would be to broaden the memory criterion. For example, you could say that it is still possible for the sleeping person to remember earlier events in their life, whereas it isn’t possible for the severe Alzheimer’s patient to remember such events. If the sleeping person were simply woken up, they would be able to remember their earlier life. But there is no simple thing that could be done to restore the Alzheimer’s patient’s memory in this way. [5]

One of the most famous objections to the memory criterion turns on the idea that numerical identity is a transitive relationship . When we say that x is numerically identical to y, we mean that x and y are one and the same object. That is, if x is identical to y and y is identical to z, must be true that x is identical to z. Once we understand this, we can see that there is a problem with the memory criterion. Suppose that Roses at age 50 can remember things about Roses at age 25 and that Roses at age 75 can remember things about Roses at age 50. Does it follow that Roses at age 75 can remember things about Roses at age 25? It should be clear that it doesn’t follow and this shows that memory is not in general a transitive relationship. Now here is the problem. According to the memory criterion two persons are identical if the later one can first- personally remember things that happened to the earlier one. So Roses at 25 and Roses at 50 are identical. Likewise, Roses at 50 and Roses at 75 are identical. But as we saw above, numerical identity is transitive, so it must follow that Roses at 25 and Roses at 75 are numerically identical. But as we have just seen, it doesn’t follow because memory is not transitive in the way numerical identity is. Therefore, memory cannot be the same as numerical identity.

Therefore, the memory criterion cannot be correct. [6] How might Locke respond to this objection? On the one hand, Locke seems happy to admit that you have not always been the same person throughout your life (since you aren’t when you’re sleeping) and that you may become a wholly different person (as in the case of Bob, above). So Locke might be content to just allow that the lifetime of Roses consists of more than one different person. On the other hand, if we are looking for a sense of personal identity that lasts throughout a person’s lifetime, then in some cases (for example, cases where there are memory failures) we will have to say that there are multiple different persons that have existed in the course of one lifetime.

Philosophers continue to debate Locke’s memory criterion, but many philosophers influenced by Locke have tended to move to a broader psychological continuity account of personal identity . On these accounts, what makes us a person numerically identical through time is that there are causal connections between our psychological states. For example, at age 10 I had a certain set of beliefs, desires, and memories (all different kinds of psychological states). At age 11 I probably had a similar set of psychological states, although of course new ones had been added and some changed. But what makes me at 11 the same as me at age 10 is that the psychological states I had at age 10 were causally involved in bringing about the psychological states I had at age 11. It is these causal relationships between my psychological states that tie me back to these older versions of myself and thus account for my persistence through time.

Psychological continuity accounts of personal identity retain the Lockean identification of our persisting identities with our psychological states, but they reject the Lockean idea that these must be consciously accessible mental states. So, in a sense, I don’t have to be able to maintain the persistence of my identity through time (for example, by consciously connecting myself now to myself ten years ago). Rather, my identity is maintained by the causal relationships between my psychological states. The result of making this relationship causal is that my personal identity can persist despite my lack of memory. This solved several of the problems that were raised for the memory criterion. For example, if I am asleep or awake my persisting beliefs, desires, and values do not change. When I am asleep, I still believe that George Washington was the first U.S. president, that water contains hydrogen atoms, that I had a piñata at my tenth birthday party, and liberal democracies are in theory the least bad form of government. What makes me the same person while I am asleep is that my psychological states while asleep are caused by my previous psychological states while I was awake. It doesn’t matter, as it did for Locke’s memory criterion, that I cannot consciously access these psychological states while asleep. Likewise, making the continuity between our psychological states causal rather than conscious solves the transitivity problem explained above. It doesn’t matter that Roses at 75 cannot remember anything about Roses at 25. Rather, what matters is that Roses’s psychological states at 75 can be traced back in causal line to Roses’s psychological states at 25. Of course, her psychological states may have changed radically in that time, but that doesn’t matter. In this way, psychological continuity accounts allow for the possibility of persistence despite radical change. And in some sense this is exactly what our common sense intuitions suggest about the persistence of our identities through time: although we can change radically, nonetheless, there is still a sense in which we remain the same.

But how radical can the change be and the individual still persist? The most difficult problem for psychological continuity accounts is called the fission problem. Suppose we perform a hemispherectomy (splitting the brain in two at the corpus callosum and then removing one half) on “Lefty” and transplant the right half of his brain into another person (call him “Righty”). The psychological continuity view would seem to imply that Lefty and Righty are the same person since both are psychologically continuous with Lefty. But it seems there are now two people whereas the psychological continuity view implies that there is only one person. This is the fission problem. One thing the psychological continuity theorist could say in response to the fission problem is that since there is a radical, exogenous causal disruption of Lefty’s psychological states (“half” of them are removed and put into another person), that Lefty ceases to exist since the causal continuity of his psychological states is disrupted. In this case, one person ceases to exist and two different ones, Lefty2 and Righty come into existence. This seems a sensible way of responding to bizarre thought experiments like the one above. After all, it isn’t intuitively obvious that Lefty continues to exist after such a radical procedure. On the other hand, if we think that Lefty remains numerically identical even after the hemispherectomy, then the psychological continuity view would imply that Righty is also Lefty and that seems to be an absurdity.

Personal identity as bodily continuity

The bodily continuity account of personal identity, as I am using that term here, contrasts with psychological continuity accounts in that it claims that what accounts for our persistence through time is our bodily continuity, not our psychological continuity. A famous argument for the bodily continuity account comes from the philosopher Bernard Williams. [7] Williams has us imagine the following sci-fi thought experiment. Suppose that you are told that you will be painfully tortured tomorrow but that before you are a certain procedure will be performed on you: all of your psychological states (memories, beliefs, desires, and so on) will be wiped clean. That is, you will become complete amnesiac, remembering nothing of who you are or were. You will become essentially a blank slate. Psychological continuity accounts would seem to imply that in this state you have ceased to exist. Thus, the person that will be tortured tomorrow will not be you. However, it seems that this would be cold comfort to the person facing this prospect. That is, it seems we would still now fear the torture that will occur tomorrow, even if none of our psychological states remain when we are undergoing the torture . To Williams, the fact that we still fear the torture implies that we do not identity ourselves with our psychological states, but rather with our bodies. How else could you explain why we would fear the torture? It seems that the psychological continuity account of our identity would say that we shouldn’t fear the torture since the person being tortured tomorrow will not be us. Be since we do fear the torture, this implies that we do identify ourselves with that individual who will be tortured tomorrow.

Williams argues that this is so even if we imagine switching all of our psychological states with another person—that is, all of their psychological states are transferred to our brain/body and all of ours, to their brain/body. Again, the psychological continuity view would seem to imply that the personal identities of these two bodies have switched: the A-body person takes on B’s identity and the B-body person takes on A’s identity. Figure 1 below is a representation of this situation.

Suppose that you are A in the above scenario and suppose that you are reasoning purely in terms of self-interest (that is, you want to avoid being tortured). Who would you say should be tortured tomorrow: the A-body person or the B-body person? Williams think that we would say the B-body person should be tortured, even if the B-body person inherits all of our psychological states ! Since psychological continuity accounts (including the Lockean memory criterion) imply that person A now exists in the B-body person, then such accounts imply that we should say that the A-body person should be tortured. The fact that we would say that the B-body person should be tortured is supposed to clearly refute psychological continuity theories, according to Williams (or at least to raise a serious problem for them). Again, what we seem to be doing in a case like this is identifying ourselves not with the continuity of our psychological states, but rather with the continuity of our bodies.

If you aren’t already convinced that if you were A, you would identity with the A- body person after the transfer of psychological states (and with the prospect of the impending doom of torture applied to the A-body person), Williams walks through a series of thought experiments, starting with the above amnesia scenario. Since he thinks we would clearly still fear torture (now) even if we were to be given total amnesia before the torture took place, he uses this to show that there is no difference between the amnesia scenario and the psychological transfer scenario, described above. Willliams walks us through the following permutations of the amnesiac scenario in order to arrive at the transfer scenario, claiming that none of the changes should make a difference to our answer of who should be tortured:

• Total amnesia
• Total amnesia + totally new memories created
• Total amnesia + totally new memories that come from some other existing person, call them “B-person”
• Total amnesia + totally new memories that come from some other existing person + your memories (that have been wiped clean) are given to that other B-person)

This last scenario is just the same transfer scenario described above. Williams claims that if you said that the B-body person should be tortured in the amnesia scenario then you should logically say the same thing in the transfer scenario, since there are no relevant changes in any of the scenarios through which the amnesia scenario is transformed into the transfer scenario.

One puzzling thing about Williams’s article is that he seems to equate transfer scenarios like the one above (where all psychological states are transferred) to brain transfer scenarios and it is not at all obvious that this is so. [8] Although it seems to me correct that we should identify with our bodies rather than our mental states in the psychological state transfer scenario, we should not identify our bodies in a brain transfer scenario. If you are A in the scenario and your brain will be transferred to B’s body, then it seems to me that you should choose the A-body person to be tortured. In this case, you won’t feel it because the seat of consciousness that underlies our experiences (whether of pleasure or pain) has now shifted, with the transfer of my brain, to B’s body. Therefore, you should choose the A-body person to be tortured. If this is right, then it seems like Williams’s scenario doesn’t really show that we identify with our bodies, as such. Rather, it shows that we identify with our brains—specifically with our first- person conscious experience that we think goes where our brain goes. (As we will see presently, Dennett’s sci-fi story will challenge this intuition.) The remains behind when we transfer all of our psychological states is the seat of conscious experience—that which is capable of experiencing pleasure and pain. The reason we would choose the B-body person to be tortured is that although they have all of our psychological states, they do not have our seat of consciousness—our first-person conscious experience. That remains behind with our brain, even if all of our psychological states are extracted from it and replace with B’s psychological states. In contrast, in the brain transfer scenario, not only all of our psychological states are being transferred, so also is our seat of conscious experience itself. But since the “seat of conscious experience” is as much a psychological property as it is a physical property (the brain), Williams’s argument doesn’t really show that we identify our persistence with some aspect of our bodies (brains) rather than some aspect of our minds (consciousness). [9]

Within contemporary philosophical debates about the persistence question, the view that aligns most closely with bodily accounts of personal identity is a view called animalism . [10] Contrary to Lockean accounts of the persistence of our personal identity in terms of our psychological properties, animalists claim that what accounts for our persistence through time is our animal properties. Yes, we are thinking animals, but we are first and foremost animals. According to animalists, our “animal properties” are the ones that account for our persistence through time as the same animal. For example, this could the biological properties that maintain the life of the organism over time—they are what keep the organism from dying and becoming, through decomposition, something else. This means that what accounts for the persistence of individual human beings through time is the same kind of thing that accounts for the persistent of individual dogs or cats or trees through time. A crucial argument that animalists make against Lockean accounts is that only animalism can make sense of the idea that I persist through time from birth to death. As we have seen, accounts which ground our personal identity in our psychological properties have to admit that my personal identity stops when there is a large enough discontinuity in my psychological states. Animalists admit that although I may cease to be a person under certain conditions (for example, if I become a complete amnesiac), I remain an animal and thus I continue to persist through time. Insofar as we think that the essence of who we are is extremely robust and persists through the kinds of radical changes that we can undergo throughout our lifetimes, animalism is an attractive alternative to Lockean answers to the persistence question.

Another argument that animalists have made is called the animal ancestors argument . Suppose, contrary to what animalism claims, we are not essentially animals. If we are not animals, then our parents are not animals either, nor are our grandparents, and so on. But this entails something that is false according to evolutionary theory: that nothing in our ancestry is an animal. But since we know this to be false, it follow that our original assumption must be false. That is, it follows that we must be, in essence, animals. This argument uses a famous form of argument called a reductio ad absurdum (this is Latin for “reduce to absurdity). The argument proceeds by assuming the falsity of a claim P that we is true and then show how if we assume the falsity of that claim P, it leads to an absurdity (strictly, a contradiction ). But since absurdities like contradictions cannot be true, if follows that our original assumption (that P is false) must itself be false, which means that P is true.

One interesting objection to animalism is the case of dicephalic twins . The problem is that it looks there are two individuals in the case of dicephalic twins. However, it seems pretty clear that there is only one animal . Dicephalic twins thus constitute a counterexample to animalism’s claim that our identity consists in our animal properties. [11]

Dennett’s “Where Am I?”

Daniel Dennett’s, “Where Am I,” is a mind-bending sci-fi short story to read in order to problematize different accounts of personal identity. [12] Arguably, problematizing the concept of personal identity, as well as different accounts of it, is exactly what Dennett was trying to do in writing the story. [13] Regardless of Dennett’s goal, what I will try to do in this section is use the story to show that there is no one way of accounting for our personal identity that can withstand the radical ways in which individual human beings might persist through time. If Dennett is correct, then it is possible that I (my identity) could be spread over many different places at one time (omnipresence!) or even that there could be two individuals that share my numerically identity! I highly recommend that you simply read the story for yourself before reading my own synopsis of it.

“Where Am I?” begins with Dennett signing up for an expedition in which he must disarm a highly radioactive object underground. Because it is feared that the radioactivity will destroy his brain, an operation is performed in which his brain is removed and placed into a vat of liquid, keeping it vital. In addition, electrodes are implanted both in the neurons in his severed brain and in the brainstem in his body so that the brain can still communicate with the body electronically, at a distance. If you doubt this could be done, just consider that the brain’s neurons are sending many, many simple messages that could be, in theory, relayed through other mediums, like radio waves. As Dennett puts it, the doctors describe the operation procedure as essentially stretching his neurons so that they can communicate with his body from a long distance (wirelessly, by electronic signals like radio waves).

Whilst on the underground expedition, something goes wrong and Dennett’s body is crushed in an accident. Before the accident it seems to Dennett, from his first-person perspective, that he is underground. However, once his body is destroyed, his point of view reverts immediately back to lab, where his brain is in a vat of liquid—miles and miles away from where he just was underground before the accident. At this point, Dennett has no body, just a brain. This would be a frightening position to be in, if you think about it. There is no sensory input, no way of communicating with the outside world. [14] While in this state of extreme sensory deprivation, scientists figure out how to stream Dennett’s favorite classical music (Brahms) straight into his auditory nerve of his brain (thus bypassing the normal way of hearing via the mechanics of our ears).

Eventually, the scientists find a new body for Dennett and connect his original brain to the new body in the aforementioned way (via electrodes in the new body’s brainstem). The newly reimbodied Dennett emerges, now able to communicate with the rest of the world again. Immediately Dennett’s point of view switches from inside the vat (where his brain is) to outside the vat, where his new body is. He walks back into the lab to the applause of all the scientists working on the project and stares at his brain inside the vat of liquid. Earlier, scientists had shown him a switch which turned on/off the transmitter that sent the brain signals electronically to/from the body. Earlier, when he had turned that switch off, his body had collapsed to the floor (since it was no longer connected to the brain). Just for kicks, Dennett now tries this again and miraculously nothing happens. His conscious experience is exactly the same; his point of view is exactly the same; nothing seems to change at all.

Puzzled by this, he asks the scientists who explain that they had actually “cloned” his brain on a computer so that there was an exact replica of his brain that was running the exact same input/output signals to his body. What the new switch did was simply change which thing was connected to his body: the original brain or the clone of his brain on the computer. The putative reason that scientists had done this was just in case Dennett’s brain was destroyed, Dennett could still live on via his “brain” that the computer had cloned. As Dennett flips the switch back and forth, he can tell no difference at all in terms of his point of view and the nature of his conscious experience. It is as if nothing had happened at all.

The last part of the story concerns another upsetting circumstance (both emotionally for the character “Dennett” in the story and philosophically for Dennett, the author of the story). Dennett’s original brain and the computer brain come out of sync with each other—the inputs and outputs no longer match—so that when the switch is thrown to switch what is controlling Dennett’s body, a whole new persona emerges (in this case, from weeks of inability to control the body). In essence, there are now two people controlling Dennett’s (new) body, but only one can control the body at a time. They both receive sensory inputs to the body, but only one can send motor signals to move the body. If you were the person who couldn’t send motor signals to reach the body, you can imagine how distressing this would be.

Below is a diagram which shows each different stage of the story.

Notice what the story seems to entail. Those who say that bodily continuity accounts for our persistence would seem to be incorrect, since Dennett seems to himself in the story to persist even though his original body has been destroyed and replaced by someone else’s body. On the other hand, those who would see our persisting identities as tied to our brains also seem to be mistaken, since we can imagine a further stage of the story (before the computer and brain came out of sync) in which Dennett’s original brain (sitting in the vat of liquid in the lab) was destroyed in a different accident and yet Dennett’s point of view remained the same. So one’s identity is not bodily continuity nor is it, more specifically, the continuity of the brain. This seems to leave open the psychological continuity accounts of personal identity. However, consider one of the paradoxical implications that this story raises for psychological continuity accounts. In the last stage of the story, before the computer and Dennett’s brain have gotten out of sync, it appears that there are two, numerically identical Dennetts , since the information (memories, beliefs, desires) on the clone of Dennett’s brain on the computer is identical to Dennett’s brain. (This is just an instance of the fission problem, explained above.)But there cannot be two, numerically identical objects. Therefore, psychological continuity accounts cannot be correct.

One might take the upshot of Dennett’s story to be that there are no good answers to the persistence questions. That is, perhaps I do not really persist through time at all. The idea that I—my “self”—does not persist through time is an old idea that also arises in older philosophical traditions, both in the East and West. The Buddhist concept of anattā (“no self”) suggests the impermanence and everchanging nature of our personal identities. [15] In the West, David Hume famously claimed that:

For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other, of heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe anything but the perception. When my perceptions are removed for any time, as by sound sleep; so long am I insensible of myself, and may truly be said not to exist. And were all my perceptions removed by death, and could I neither think, nor feel, nor see, nor love, nor hate after the dissolution of my body, I should be entirely annihilated, nor do I conceive what is farther requisite to make me a perfect non-entity. If anyone, upon serious and unprejudiced reflection thinks he has a different notion of himself, I must confess I can reason no longer with him. All I can allow him is, that he may be in the right as well as I, and that we are essentially different in this particular. He may, perhaps, perceive something simple and continued, which he calls himself; though I am certain there is no such principle in me. But setting aside some metaphysicians of this kind, I may venture to affirm of the rest of mankind, that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement. [16]

Perhaps Hume and the Buddhists are correct. After all, we have seen that there are difficult problems that arise for the different answers to the persistence question. But even if there is no persisting self, it is nevertheless true that many people have the sense that there is. A separate question concerns how to best explain where our sense that we persist through time comes from. In the last couple of decades, an interdisciplinary view has become very influential: the narrative conception of the self. In the next section we will consider this view.

The narrative conception of the self

Why does it feel to me that there is a persisting self? According to the narrative conception of the self, what unifies our lives—that is, what makes it seem that me at 10 years old is the same as me at 43 years old—is the stories we tell about ourselves that connect the different parts of our lives. For example, I, Matthew Van Cleave, am the person who grew up in a small town, became a runner in high school and college, played in a rock band in college, and then after college decided to become a philosopher and so went back to graduate school to earn a PhD in Philosophy. Furthermore, narratives have a certain kind of structure to them: there is beginning, middle and end. Importantly, the end of the narrative is what enables us to make sense of and assess who we are at any point within the narrative. The end of the narrative is what provides guidance throughout the narrative: what counts a good or bad decision is relative to the end goal/purpose of the life whose narrative is being narrated. For example, if the end of my story concerns being a successful philosophy professor and having a profound impact on my students and colleagues, then this end is what my life is working towards and the parts of my life constitute my self insofar as they are a part of this narrative structure. According to the narrative view of the self, who we are is just the story that we tell about ourselves. Notice that the story we tell about the events is different than the events themselves. The narratives we construct of our lives are post-hoc (Latin for “after this”) in the sense that we construct them after the events have already happened. But as mentioned above, a narrative can also exert a normative influence over what we choose to do in the future. For example, I might choose not to take a much higher paying job in the business world because it doesn’t cohere with my narrative of myself as an influential and respected philosopher. Or I might decide to return the credit card I found on the sidewalk instead of trying to use it because using it would be inconsistent with my narrative of myself as an honest person.

The narrative conception of self is compatible with the idea that there is nothing metaphysically deep about the self. The narrative that I construct is just one of many different possible narratives that could be constructed from the same raw material of my life—my experiences, memories, interests, commitments, and so on. Whereas philosophers have traditionally tried to respond to the persistence problem by searching for something within those raw materials that unifies our self and explains our persistence, the narrative view sees the unity as something imposed from the outside—from a narrator. Thus, like the example of the ship in the beginning of this chapter, the narrative view views one’s identity as an extrinsic property (like the mere fact that the ship was always called “TS”) rather than as an intrinsic property. Perhaps a good analogy would be currency. Consider what makes a 100 dollar bill valuable. It certainly isn’t the paper an ink which constitutes the bill. Rather, it is the complex set of rules and institutions outside of the 100 dollar bill that gives it value. If you were to destroy that system (for example, if the government were overturned and all of the institutions like the Federal Reserve that bestow value on the 100 dollar bill ceased to exist), the 100 dollar bill would no longer have its value. It would simply be a piece of paper with some ink on it. Likewise, according to the narrative conception of the self, the fact that there is a persisting self depends on our ability to impose a story on our lives. If we lost that ability, there would be no persisting self although there would still be experiences, memories and thoughts. For the narrative view, the persisting self is an abstract entity that we construct from the raw materials of our lives and which, once constructed, exerts guidance on our lives.

One problem with the narrative view is that it defines the self too narrowly. If the existence of a persisting self requires a narrative arc with a beginning, middle, and end, then many individuals’ lives will lack this structure, for example, because their lives ended early. Such lives would seem lack any persisting self, if the narrative view is correct. Moreover, there are many people who have a sense of themselves as persisting through time although they don’t really have any grand narrative of their life. For this reason and others, some philosophers, such as Elisabeth Camp, have suggested thinking about our constructed identities not in the narrative, beginning-middle-end way, but rather thinking of ourselves as characters in an unfolding story whose end we don’t know yet. The main difference is that whereas the narrative conception holds one’s interpretation of their life hostage to the end of the story, the character conception doesn’t. Instead, what guides our interpretation of our lives is a “particular nexus of dispositions, memories, interests, and commitments.” [17] The interpretation that we create can also be constrained by information we glean about ourselves from other people, such as our friends.

Study questions

• True or false: The persistence question asks whether or not there exists a momentary awareness of ourselves as agents.
• True or false: There are two main types of answer to the persistence question.
• True or false: John Locke’s view of personal identity is a kind of psychological continuity view.
• True or false: According to Locke, if our DNA always stayed the same, this would be a good answer to the persistence question.
• True or false: DNA could serve as a good criterion of numerical identity.
• True or false: One of the most difficult problems for the psychological continuity account is the fission problem.
• True or false: The fact that we should fear torture to our body even if all of our psychological states have been transferred to a different body is supposed to provide support to the bodily continuity account of personal identity.
• True or false: According to Locke, “person” is a forensic term.
• True or false: Animalism is a type of bodily continuity account of personal identity.
• True or false: Dicephalic twins pose a problem for animalism.
• True or false: Dennett’s science fiction story suggests that a person can continue to persist despite having neither a brain nor a body.
• True or false: Narrative accounts of the self are compatible with the idea that there is no persisting self.

For deeper thought

• What does it mean to say that “identity is a transitive relationship”? Explain how Locke’s memory criterion conflicts with the idea that identity is transitive.
• Whereas Lockean accounts are interested in accounting for how persons persist, animalists think that we should be explaining how organisms persist. Think of an example where the organism continues to persist while the person doesn’t.
• Explain the sense which the narrative account of the self makes our identities external to us. How does this different from traditional accounts of the persistence of the self?
• How is sleep a problem for Locke’s memory criterion?
• Suppose that we say that the identity conditions of a self are simply the object that traces a continuous spatio-temporal path. What makes me the same person as I was when I was 10 years old is that the body of my 10 year old self and the body of my 43 year old self has traces a continuous, uninterrupted spatiotemporal path. Would psychological continuity theorists accept this account? Why or why not?
• Suppose that in Williams’s transfer scenarios we transfer our whole brain from one body to another. Does this change your answer of who will be tortured? Why or why not?
• Why might Williams’s transfer scenarios really prove that we identify with our bodily properties rather than with our psychological properties?
• This thought experiment is quite old—going back to Ancient Greece at least—but the first record of it we have in writing is from Plutarch. He writes: “The ship wherein Theseus and the youth of Athens returned had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.” ↵
• I say “human being” rather than “person” here because as we will see below, different answers to the persistence question may or may not focus on the identity of persons. “Human being” is a broader term which leaves open the question of personhood. For example, I have always been a human being, but (depending on one’s view) I may not have always possessed personhood (for example, when I was an infant) and I may continue to persist as a human being even if I am no longer a person (for example, if I lose all of my brain functioning). ↵
• Some philosophers have claimed not to have the sense that they are the same person from one moment to the next. David Hume famously claimed ( A Treatise of Human Nature, book 1, part IV, section VI ). that we did not have any awareness of a persisting self. And the Oxford philosopher Derek Parfit came to see one’s sense of identity is a kind of illusion and that it doesn’t really matter that we do not persist as persons—in fact, that it can actually have salutary effects on one’s ethical stance towards the world. More on this idea in the last part of the chapter. ↵
• John Locke, An Essay Concerning Human Understanding , book 2 , chapter 27. ↵
• Some philosophers would put this point in terms of “possible worlds.” You could say that there is a “nearby possible world” in which, say, Bill, who is merely asleep, could remember earlier episodes of his life (all you have to do is wake Bill up). In contrast, there is no nearby possible world in which Bob, who as severe Alzheimer’s, could be made to remember earlier episodes of his life. ↵
• This objection to the memory criterion of personal identity was originally raised by Thomas Reid in his Essays on the Intellectual Powers of Man (essay 3 , chapter 6), which was published in 1785. Reid says: "Suppose a brave officer to have been flogged when a boy at school, for robbing an orchard, to have taken a standard from the enemy in his first campaign, and to have been made a general inadvanced life : suppose also, which must be admitted to be possible, that, when he took the standard, he was conscious of his having been flogged at school, and that when made a general he was conscious of his taking the standard, but had absolutely lost the consciousness of his flogging. These things being supposed, it follows, from Mr. Locke's doctrine, that he who was flogged at school is the same person who took the standard, and that he who took the standard is the same person who was made a general. Whence it follows, if there be any truth in logic, that the general is the same person with him who was flogged at school. But the general's consciousness does not reach so far back as his flogging therefore, according to Mr. Locke's doctrine, he is not the person who was flogged. Therefore the general is, and at the same time is not, the same person with him who was flogged at school." ↵
• Williams, Bernard, 1970, “The Self and the Future,” The Philosophical Review , 79: 161-180. Reprinted numerous times/places. ↵
• Williams (1970), p. 162. ↵
• The question of the relationship between our brains and our consciousness is thorny philosophical question. Some philosophers think that consciousness reduces to brain processes while other thinks that consciousness cannot be strictly reduced to brain processes. For more on this topic, see the chapter in this textbook on the mind-body problem. ↵
• See the Stanford Encyclopedia of Philosophy entry here: https://plato.stanford.edu/entries/animalism/ ↵
• See McMahan, Jeff, 2002, The Ethics of Killing: Problems at the Margins of Life, Oxford: Oxford University Press, p. 32. ↵
• This was originally published in Dennett’s, Brainstorms (Bradford Books, 1978) and has been reprinted many times in different places. ↵
• That this was one of the things he was attempting to do in this piece was in fact confirmed to me by Dennett in personal correspondence (Snapchat—just kidding, email). ↵
• Aficionados of the heavy metal band Metallica will recognize this kind of situation as one portrayed in the song, “One.” ↵
• One excellent representation of the doctrine of anatta comes from the Buddhist text, The Questions of King Milinda (Book 2, chapter 1) in which the Buddhist sage, Nāgasena, explains to Milinda that just as a chariot is nothing in additions to all its parts, so the self is nothing in addition to all of its parts. ↵
• David Hume, 1739, A Treatise of Human Nature (book 1, part IV, section VI) . ↵
• Elisabeth Camp, “ Wordsworth’s Prelude, Poetic Autobiography, and Narrative Constructions of the Self. ” ↵

Introduction to Philosophy Copyright © by Matthew Van Cleave; Paul Jurczak; Christopher Schneck; and Douglas Sjoquist is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Who am I? The Philosophy of Personal Identity

The various problems of personal identity pose difficult, yet essential questions for the entire field of philosophy as a whole.

Personal identity is a philosophical issue which spans a whole range of disciplines within philosophy, from the philosophy of mind, to metaphysics and epistemology , to ethics and political theory. There is no one problem of personal identity – they are rather a kind of philosophical problem that starts to emerge whenever we ask questions about what one ‘is’ most fundamentally.

Problems of personal identity were first posed in something like the form they take today, but underlying issues of personal identity have been a feature of the Western philosophical tradition since its inception. Plato , writing near the dawn of philosophical enquiry, and Descartes writing at the dawn of modern philosophy, both had a theory of what we were most fundamentally – namely, that we are souls. This illustrates that it is very difficult to undertake any extensive philosophical enquiry without coming up against some problems of personal identity.

Personal Identity: A Variety of Questions, a Variety of Answers

Some of the usual answers to the question of personal identity – ‘I am a human being’ or ‘I am a person’ or even ‘ I am a self ’ – are sufficiently vague as to be worthy of further philosophical analysis. Some of the problems of personal identity involve trying to define terms like ‘human’ or ‘person’ or ‘self’. Others ask what the conditions are for the persistence of a human or a person or a self over time; in other words, what it takes for a person or a self to persist.

Still, others ask what the ethical implications of these categories actually are, or whether what matters in an ethical sense has anything to do with what we are most fundamentally at all. In other words, some question whether personal identity matters . How we respond to one problem of personal identity is likely to (partly) determine how we respond to other problems of personal identity. It is therefore justified to think about personal identity in terms of general approaches to it as an issue, rather than specific responses to specific problems.

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Please check your inbox to activate your subscription, the ‘physical’ approach.

Before going through several problems of personal identity in depth, it is worth distinguishing some of those general approaches now. There are three broad categories of approach to personal identity. The first is what we can call the ‘Physical’ approach: this locates what we are fundamentally in something physical. Some theories of this kind say that what we are most fundamentally is our brains, or some part of our brains – be it a specific part, or just enough of our brains. The underlying thought here is generally that our minds only exist as they do because our brains are a certain way, and whilst losing (say) a finger or even an arm couldn’t possibly turn someone into a wholly different person, removing or altering their brain might. Other theories of this kind refer to a range of physical features, which together define us as a biological organism or a species.

The ‘Psychological’ Approach

A second approach to personal identity says that what we are, most fundamentally, is not any physical organ or organism, but something psychological . We can call these ‘Psychological’ approaches. We might be understood, as Hume did, as a succession of perceptions or impressions . We might also be understood as consecutive psychological connections. What differentiates these two is the view that certain kinds of mental states constitute relations which hold over a span of time. Memory is especially significant here. For instance, there is a relation between my mental state as I recall agreeing to write this article, and the time at which I agreed to write this article. The idea that what we are fundamentally relies on such connections is a highly intuitive one. If someone were to have their memories wiped, or switched out for someone else entirely, we could imagine calling into question whether the resultant person is the same as the one which existed before their memory was altered.

The ‘Sceptical’ Approach 

A third approach to personal identity calls into question the reality of the problems of personal identity, or is sceptical about our ability to answer them correctly. We can call these ‘Sceptical’ approaches. This approach says that there is no answer to questions concerning personal identity, or that they are the wrong way of asking questions about ourselves and our mental lives, or that whatever answer we give to these questions isn’t really important.

There are broadly three kinds of sceptical approaches. First, that which holds we ‘are’ nothing at all, most fundamentally. There is no core to our existence, no final kernel of truth about what we are which trumps all others – one influential statement of this view comes from Ludwig Wittgenstein’s Tractatus Logico-Philosophicus . Second, that which holds that there is no answer to this question because it is the wrong kind of question, focusing too much on the concepts by which we understand ourselves rather than the source of our mental lives. This approach might say that what we are most fundamentally is a question best left to the natural sciences. Third, that which holds that whatever we are fundamentally does not seriously affect how we should see the world, or morality.

The Ship of Theseus

This last view is worth considering in more detail, as we move on to consider specific problems of personal identity in more detail. Before exploring it further, it is important to clarify that personal identity is often considered a species of the yet-more-numerous problems of identity simpliciter . Perhaps the archetypal problem of identity is explained using an example, commonly called the ‘Ship of Theseus’ problem . The thought experiment is this: imagine a ship which, over time, has every plank, every mast, every patch of sail, indeed every single part of it replaced with a new component. Even if the shipbuilder or the captain tries very hard to make a like for like replacement, no two planks of wood are exactly alike. The questions this raises are these: is the ship with all of its component parts changed the same ship it was before a single component was removed? And, if it is not, then at what point did it become a different ship?

Enter the Teletransporter

This doesn’t even begin to cover some of the many interesting problems of identity, but it does begin to illustrate how problems of personal identity can be conceived in similar terms. Derek Parfit illustrated one such problem using an imaginary piece of technology known as a ‘Teletransporter’. This piece of technology obliterates every cell of one’s body and brain, traces it, and then replicates it somewhere else almost immediately. This is experienced by the person in the Teletransporter as something like a brief nap, after which they awake at their destination otherwise unchanged. Intuitively, if such a piece of technology existed, we might be inclined to use it. If I awake with my body and mind unchanged, what’s the harm?

Problems of Replication

That is, until Parfit changes the thought experiment and asks us to imagine what would happen if we were replicated instead. Now when we awake unaltered, there’s a version of me remaining unchanged back wherever I came from. How does that change my perception of this procedure? What if I were to awake from Teletransportation with a heart defect, but would know that my Replicant was going to be perfectly healthy, and so would be able to live my life as I had been up till that point. What all of this head-spinning, science fictional thinking is meant to elicit is the sense that how we respond to one problem of personal identity may be intuitive, but applying the same logic to other problems of personal identity might leave us with some quite perverse conclusions.

Reductionism – A Skeptical Solution?

Parfit’s response to all of this isn’t to offer his own, separate approach to the problems of personal identity. Rather, he argues that personal identity does not matter. What matters is not some fundamental kernel of the self, some criterion of personhood, or some other ‘deep’ fact about ourselves. What matters are the things we know to matter, namely the categories of our mental life that are self-evident. Our memories, our perceptions, and the ways in which we describe our lives to ourselves.

This approach to personal identity is often labelled ‘Reductionist’, but perhaps a better term would be ‘Anti-Contemplative’. It doesn’t advocate that we answer difficult questions by excavating deeper and deeper until we find what we are fundamentally. It suggests that this manner of reflection is unhelpful, and rarely offers us consistent answers. The problems of personal identity are endlessly fascinating, and far broader than can be summarized in one article. The relationship between the various problems of personal identity is itself a matter of debate.  Eric Olsen holds that “There is no single problem of personal identity, but rather a wide range of questions that are at best loosely connected”.

Personal Identity: Implications for Philosophy in General

This is, of course, another explanation for why no single conception of ourselves appears to meet all of the problems of personal identity. Equally, problems of personal identity raise a number of ‘ metaphilosophical ’ questions; that is, questions about the nature of philosophy itself and the methodology one should adopt when undertaking it. In particular, it raises the question of whether there is a natural hierarchy within philosophy in terms of which questions should be answered first, and thereby determine our answers to other philosophical questions.

It is often implicitly understood that while our conclusions about how our minds are can influence our conclusions about ethics, our conclusions about ethics cannot influence our conclusions about our minds. This kind of priority comes under question at the point where we start to take an – already convoluted and contradictory set of responses to questions about our minds – and engage with them not by attempting a somewhat ramshackle unified response, but rather asking what actually matters to us, both in the realm of ethical reflection and in the less reflective arena of our everyday lives.

Epistemology: The Philosophy of Knowledge

By Luke Dunne BA Philosophy & Theology Luke is a graduate of the University of Oxford's departments of Philosophy and Theology, his main interests include the history of philosophy, the metaphysics of mind, and social theory.

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