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Look at what I just read in Stanford Encyclopedia of Philosophy: "2. You could

Look at what I just read in Stanford Encyclopedia of Philosophy: "2. You could not have been born of different parents. (Someone born of different parents wouldn't be you.) (...) Each of these claims appears to have a true reading." Do you all think this way? A son of my paternal twin-uncle and my maternal twin-aunt could easily (so to say) have exactly the same DNA as I have. He could have been born on the same day. He could have been told that his parents were my actual parents. He could have been given my name. My actual parents could have had no biological child. Things in the whole world could have been exactly as they actually were and are since then. So, in what reasonable sense wouldn't this person be me?

Interesting question. Can't we interpret the story you told as one in which you never exist but someone quite similar to you does instead? Why would such an interpretation be unreasonable?

You list six conditions that you seem to regard as jointly sufficient for someone's being you: (1) having exactly your DNA sequence; (2) being born on your birth-date; (3) being told that your parents are his parents; (4) being given your name; (5) your parents' having no biological child; (6) all else being equal.

None of those conditions is individually sufficient for someone's being you. (1) Given identical twinning or cloning, someone else (your twin or clone) could have exactly your DNA sequence; (2) plenty of other people share your birth-date; (3) someone else could be told that your parents are his parents (and has been if you have a brother); (4) someone else could (and may actually) share your name; (5) your parents' having no biological child is certainly not sufficient for someone's being you; (6) ditto for "all else being equal."

So why think that when we combine (1)-(6) we get you? What is it about the combination that forces us to regard the result as you?

I am writing a book dealing with Alzheimer’s disease for young people. The

I am writing a book dealing with Alzheimer’s disease for young people. The protagonist, a boy in the 8th grade, is grappling with his grandmother’s progressing AD. I would be interested on your thoughts about identity/mind and Alzheimer’s disease. Is a person with progressive AD the same person that they were without the disease? Any resource suggestions would be appreciated. The boy is in a philosophy class at his Catholic school and much of his questioning will come through class discussions

This is a really interesting question. John Locke, in his Essay Concerning Human Understanding, famously defined a person as "a thinking intelligent being, that has reason and reflection, and can consider itself as itself, the same thinking thing, in different times and places; which it does only by that consciousness which is inseparable from thinking, and as it seems to me, essential to it." He then goes on to talk about our personal identity over time: "For, since consicousness always accompanies thinking, and it is that that makes everyone to be what he calls self, and thereby distinguishes himself from all other thinking things, in this alone consists personal identity, i.e., the sameness of rational being; and as far back as this consciousness can be extended backwards to any past action or though, so far reaches the identity of that person."

The notion of consciousness extending backward is often taken to signify memory, and so a Lockean theory of personal identity suggests that person A at time t2 will be the same person as person B at time t1 if and only if person A remembers some experience/s of B's. This Lockean memory theory would thus suggest that, in many cases of progressing AD, the AD patient is not the same person as she was 10, 20, 30 (etc.) years ago -- if she doesn't have any memories of experiences from that time, then the AD patient is literally not the same person as the person who had those experiences.

Nowadays many philosophers who are inclined toward a Lockean view actually endorse a broader psychological theory, rather than a narrower memory theory, so that what matters are not just connections of memory but rather more general psychological connections. Depending on how far the AD has progressed, however, these other psychological connections may be missing as well.

But as plausible as the psychological theory sounds, it is very hard not to believe that it's still Grandma who is there, afflicted with this disease. After all, we still visit her, we care about how she's treated, we haven't yet held a funeral, her will has not been probated, etc. etc. So we seem to have some conflicting intuitions on this score, intuitions that suggest that something other than psychology might be involved in personal identity. There are other philosophers who argue that bodily continuity is what matters, and yet others who have focussed specifically on the brain (even if the brain does not support the same psychology over tiem). So the whole subject is very tricky indeed.

You may be interested to read John Perry's Dialogue on Personal Identity and Immortality, which is a short and accessible treatment of many issues that will be relevant to your project. Good luck with it!

If a person has a multiple personality disorder, are they one individual, or

If a person has a multiple personality disorder, are they one individual, or several individuals?

What used to be called multiple personality disorder (MPD) is now called dissociative identity disorder (DID) in DSM, the Diagnostic and Statistical Manual of Mental Disorders, and the change in terminology may reflect a possible change in thinking. A personality (e.g. a television personality) is in one sense a person, but generally I and my personality are not the same (Same what? Same entity, presumably, if that is any help!) In any case, since my personality might change considerably over time, while I remain the same person or the same individual (I assume that individual and person, as they are applied to human beings, are equivalent concepts), the two cannot be identical. And most of us do exhibit slightly different personalities, for example at home and at work, or with friends and with superiors. Those who have a mixed ethnic or national heritage can sometimes find that they have two personalities, say one English and one Indian. They may feel the pressure on the integrity of the person. But since personality and person really are distinct concepts, they should not feel this pressure. After all, if Mr. X, who is half in Indian culture and half in English culture - as though there were only one of each! - commits some awful crime, then it is Mr. X who will be punished, no matter which personality he is manifesting or which country he is charged in. The two concepts, of personality and of person, could without too much of a stretch be called the psychological and logical (or metaphysical) concepts, respectively. Now the question is whether a change in the application of the psychological concept forces a change in the application of the logical or metaphysical concept. The answer to this seems to be negative, as I have said. Certainly if we say that in DID we are confronted with two or more individuals or persons, individuals falling under the category of person, we are implicated in a psychological concept of personal identity rather than a physical one. The criterion of identity is not the body, but the consciousness. This was Locke's view, and in the Essay concerning Human Understanding he proposes a celebrated thought-experiment in which the consciousness of a prince, and with it the soul of the prince, is transported into the body of a cobbler. The question he asks is whether the person before us is the cobbler or the prince, and his answer, relying on the consciousness criterion, is that it is the prince, although he also says that the man or human being is the cobbler. Now all we have to do is to imagine the prince vacating the cobbler's body, and the cobbler's consciousness taking up residence there again, and we have a description of DID as it might be seen by the proponent of the consciousness criterion. Overall, given that the concept of a person is partially a forensic or legal one ('It is a Forensick Term . . .'), as Locke observes, as well as a metaphysical and logical one, and given the improbability of Locke's scenario, it seems better to say that in DID what we observe is an oscillation between personalities, not individuals, though one marked by the extremeness of the difference between the personalities and the lack of communication between "them", manifesting as memory loss. This is supported, I think, by a consideration of the proposed origins of DID in childhood trauma.


Hi, I observed in lot of books and articles, the phrase "Who am I?". My question is why we need to know this answer and what is the starting step? with best regards, vikram

Philosophers have tended to think this question (who am I?) is pretty foundational, because it seems that some kind of answer is necessary in the course of addressing such questions as: what should I do with my life? What can I know about the universe or God or right and wrong? What sort of political form of government should I support? Where did I come from? Do I owe any obligations to my parents or society or the state or the religion in which I was raised? Am I a Jew, Christian, Muslim, Hindu, Buddhist, atheist, agnostic......or some combination? What can or should I hope for in life or (if there is one) a next life? One of the earliest philosophers in the west, Socrates, is said to have claimed that the unexamined life is not worth living. Whether he was right or not, it seems that without some self-examination (what do I really desire? what sort of a person am I? do I actually care about others or am I faking it?), it is very difficult to grow, to love others (if I do not know who I am, how do I know whether I love someone else?) or to dedicate your life to some great value (justice, compassion, and more).

Personally, I am on the Socratic side in this matter, but one might also worry that the question "Who am I?" is pretty individualistic, and so it might be good to balance with a question like "Who are we?" and then think who is included in the "we."

As for first steps in addressing the question of personal identity: I would recommend something Augustine (5th century) thought, and that is, your identity is partly a matter of what you love and desire. So, one thing to ask yourself is: what or whom do you love and why? The object of your love may be a person or a community or family or yourself or an ideal or God or... Augustine thought that you need to begin with some kind of self-knowledge and then find a community of fellow inquirers who welcome the practice of philosophy -- a community which genuinely seeks to love wisdom. Such a community might even suggest that the first question of the greatest importance is: What is wisdom? For a great beginning book in philosophy I recommend a classic, The Story of Philosophy by William Durrant. It is hardly ever used today, and is flawed in this or that way, but it is a narrative history of philosophy that is exciting, written with passion, and will take you on a journey through lots of different philosophical ideas about wisdom.

Good wishes, Vikram! Charles

Philosophers debate persistence conditions for personal identity because

Philosophers debate persistence conditions for personal identity because everything about us seems to change, including our cells, our memories, and our bodies. But DNA doesn't change and it codes for specfic traits in every cell of the human body. It's true that we experience changes in the way phenotypes are expressed in particular experiences or memories, but why not conclude that DNA is the ultimate source of personal identity? Philosophers don't seem to give this biological candidate serious consideration. Can you tell me why?

DNA does change. There are "point mutations", for example, in which say a single nucleotide changes, say from guanine to cytosine. . . . CTG TCA . . . becomes . . . CTG GCA . . . If there is a strand of DNA that suffers such a change, is it then not the same strand of DNA? This is exactly like the question whether persons become different persons if they lose say half a finger. And now we have the problem of DNA identity. When are two descriptions sufficiently similar to count as descriptions of the same strand of DNA? Anthony Quinton has the general issue right, in a 1962 article in the Journal of Philosophy called "The Soul": 'No general account of the identity of a kind of individual thing can be given which finds that identity in the presence of another individual thing within it. For the question immediately arises, how is the identity through time of the identifier to be established? It, like the thing it is supposed to identify, can present itself at any one time only as it is at that time. However alike its temporally separate phases may be, they still require to be identified as parts of the same, continuing thing.' By the way, 6% of identical twins do not have identical DNA, so the members some pairs of identical twins would be metaphysically identical and some would not.

It's absurd to say "If I were him I would have behaved differently" right? I

It's absurd to say "If I were him I would have behaved differently" right? I mean, if you were him you would BE him, all his atoms and neurons and flesh, etcetera, and you would have the same thoughts, desires, impulses, everything. (Unless there's some transference of my Cartesian Ego or soul or something that can rise above the fact that I'm simply just him now, but at this point that seems ridiculous unless there's a god, although I know some dualists might disagree). We so often speak as if we can judge other people's actions by just inserting ourselves into "their shoes", but can we really do that and make any sense? Thanks a lot!

You're right to detect absurdity in the literally construed antecedent "If I were him." (It's also ungrammatical: "If I were he.") There's good reason to think that statements of identity and distinctness (i.e., non-identity) are noncontingent: they never just happen to be true. So, given that you're not identical to him, you couldn't have been identical to him, regardless of the existence of God or a Cartesian ego. In that case, "If I were he" is an impossible antecedent, which (on the standard semantics for conditionals) makes the entire conditional "If I were he, then p" trivially true no matter what statement p is: "If I were he, I wouldn't be he" comes out true, for example.

But that's all metaphysics and semantics. As you say, the real point of statements beginning "If I were him [or he, or you]" is to offer advice or to pass judgment on someone's actions. It assumes that you can imagine being in his circumstances in all the relevant respects and that the relevant respects needn't include every detail of his circumstances: some details of his circumstances (such as his exact mass to the nearest gram) aren't relevant to whether his actions in those circumstances count as wise or foolish. Our default position seems to be that a detail of his circumstances doesn't bear on the wisdom or foolishness of his actions unless there's reason to think that it does.

My father replaced the lenses on his glasses. Then he replaced the frame when it

My father replaced the lenses on his glasses. Then he replaced the frame when it later broke. Same type of lenses and same model of frame. He claims they're still the same pair of glasses. When I argue he's wrong and that they're now a different pair, he claims the same could therefore be said of him as he's replaced all his cells several times since he originally bought the glasses but, since he's still him, the glasses are still the glasses. Who's right?

A CLASSIC case! This is a major issue going back to ancient philosophy. The example used then was the ship of Theseus (a Greek hero). Imagine you have the ship of Theseus and a similar ship side by side. First you switch one part (the mast, say). Is the ship of Thesus still the same? Many of us want to say 'yes,' but then we get puzzled as more and more parts are switched until eventually it seems the ships have changed places. One route that philosophers have taken might bring peace to your family: some philosophers distinguish a strict sense of identity from an identity that is "popular and loose." On a strict view, you are right. Any object with parts is not the same if even a single part is removed. This is technically called mereological essentialism. According to mereological essentialism, your father's body today is not identical with the body he had as a boy. You might even suggest to him that while he went to first grade, that (pointing at his body) did not. You can retain mereological essentialism while also allowing that sometimes we can and should meaningfully speak of sameness of identity that is not strict. In the later, though, there will be different conventions that come into play. So perhaps there is a way to allow that you both may be right? If push comes to shove, however, I am on your side on this. For a defense of our view, see the book Person and Object by Roderick Chisholm.


Hi A common response to the question of life after death is that it can't exist because of an identity problem- i.e. if I was reincarnated I would no longer have my memories and therefore not be me...However isn't this more a problem of perception rather than identity. When I go to sleep at night I am still 'me', even if I have bizzare new memories and have taken on some odd new shape and form. Similarly, if I forget a large part of my dreams, is this some form of mini death?

Great question and suggestion! While some philosophers (most notably John Locke) have claimed that the key to personal identity is memory, probably the majority of philosophers today do not. Most grant that you might endure as the self-same subject despite all kinds of memory loss and replacement.... So, if it is a fact that no one does remember their past lives, it would not follow (on many accounts of what it is to be a self), this may be only a problem of epistemology and we cannot from that alone assume that reincarnation is false. Probably one reason why some today think reincarnation cannot occur is because they think that for reincarnation to occur, a person (self, subject, soul, mind) would need to switch bodies. Those of us who are dualists or who think there is something to persons more than the material body, may well grant that it is possible for a person to come to have a new body. But materialists who think that you and I are our bodies will have grave doubts about whether we can survive the destruction of our bodies.

I am transitioning from male to female, along with physical changes I notice

I am transitioning from male to female, along with physical changes I notice changes in my thinking and emotions. Am I the same person or am I becoming some one else? How do we know who we are and do we become different people over time?

You are a good guide here since you are undergoing the changes. Presumably you have initiated this process because you feel that you are really not the gender you started off as, and so your notion of personal identity was quite complex even before the process got underway. Clearly we change all the time, and sometimes so radically we come to believe that we are quite different from how we were in the past. You are in the interesting position of perhaps feeling that you are finally approaching becoming the sort of person you "really" were all the time, and you are thus in the best position to report on how your feelings make up this changing self-perception. Self-identity is clearly far from a simple notion and nothing evidences that so much as your course of action.

I have recently been thinking about a comment that one of my philosophy

I have recently been thinking about a comment that one of my philosophy professors made in college that has been causing me a great deal of distress. He said "If you have a problem that you don't want to deal with, go to sleep and let someone else deal with it." meaning that the person who wakes up in the morning is not the same as the person who went to sleep the night before. Is there any validity to this claim? Does our consciousness continue while we sleep or does it stop and then restart? Is the person typing this question the same person who will wake up in my bed tomorrow? If we were replaced each morning by a person with identical memories, wouldn't it appear the same from the inside and the outside? And finally, is this worth getting worked up about? thanks

As I posted this, I saw that Donald had offered a similar reaction. But since I'd already written this up...

It's a very interesting topic you've raised, and one on which philosophers have written a great deal. My view fall into the blunt, even philistine category, but I'll point to other views as well.

Let's begin with your final question: is this worth getting worked up about? My answer is that it's not. What's at stake is whether some highly abstract, theoretical, and hard-to-settle metaphysical claims are true. Even if they are, life will go on as usual. You'll still experience things, remember things, look forward to things, make plans, carry them out, and in general live a human life. If there's some sense in which there isn't a single "person" that lives this life, the most psychologically healthy response is probably a shrug.

You ask whether our consciousness continues while we sleep, or whether, on the other hand, it stops and restarts. One way to read that (probably not the best way) is whether there's some mental "thing" that exists continuously throughout our lives. If that's the question, the best answer is that there's no good reason to think so. But unless we work ourselves into a philosophical lather, there's also no good reason to think that there has to be such a thing for you to be the same person who went to sleep last night. On another, probably better reading, the question is whether there's always some sort of conscious experience going on inside us (I'm treating dreams, for example, as conscious experience for this purpose) even when we're deeply asleep. Though I don't know for sure what the answer is, my impression is that there isn't. But it's not clear why I should care. Why think that for me to persist, there must be an unbroken stream of experience?

People are complicated. We have bodies with brains. The brains, it seems, are what lets us have thoughts, feelings and experiences. The goings-on in our bodies (brains included) fit together in ways that are deeply fascinating. We've learned a lot about how the more straightforwardly biological aspect work, and also how the minds that our brains give rise to work. Some of the things we learn lead us rightly to think of ourselves differently. For example: we know that we're neither as rational nor as psychologically unified as we might have thought we are. That's interesting and important. It also may be better for some purposes to think of ourselves as a complicated set of processes than as "things," but even if it is and even if we do, life goes on.

The Buddha taught a doctrine of "no self," which seemed to mean that there is no persisting inner object worth being called The Self. That's quite plausibly true. And Buddhism's view that we get out of whack when we get attached to the passing show of experience, wanting to control it and bend it to our will, is in my experience a wise teaching. Matters of living wisely aside, many philosophers have offered views of personal identity that have a lot in common with the Buddha's; the 18th century Scottish philosopher David Hume ad contemporary philosopher Derek Parfit are two notable examples. But very few of our human concerns call for getting the right take on tricky matters of metaphysics. When you think about it, that's a very good thing.