Personal Identity Through Time

Personal Identity Through Time

Personal Identity Given a person A at one time and a person B at a different time, what must be the case for A and B to be the same person? We connect a lot of things to personal identity. For example (i) Whether or not you are blameworthy for a crime depends on if you are the same person as the person who committed the crime (ii) Similarly, if I regret something, it must be something from my past (iii) If I am excited about some future good event, I care about whether the good event will happen to me or to someone else. (iv) I care about whether or not I can surive a procedure (v) If God promises me an afterlife, I want to know if I will be the one experiencing it. Notice that for all these things, qualitative change can be consistent with identity across time, and qualitative identity does not guarantee identity across time (e.g. I don t really get that excited if someone else who is just like me is going to win the lottery tomorrow) Thus, personal identity can be distinguished from exact similarity (qualitative identity) and from self-conception (e.g religious identity, vocational identity, gender identity, etc.).

Mereological Essentialism Initially, it seems like having the same body seems like a good criteria; however, it is not always clear when two things have the same body We could define a precise criteria of bodily sameness as follows: Mereological Essentialism Object A and object B are the same object if and only if they have all the same parts. However, this view seems bad for at least 4 reasons 1. It requires that we can identify the same parts across time (though perhaps this is easier at the atomic level). 2. It is false that I have all the same parts that I had when I walked in the classroom, but I am still the same person. 3. It is not clear what counts as a part of you (e.g. food in your stomach) 4. It is possible you have all the same parts as some person thousands of years ago, but clearly you are not the same object.

The Prince and the cobbler A different objection to defining personal identity in terms of of bodily identity comes from John Locke. He asks us to consider a body switching case such as a story about a Prince and a cobbler. Most people are inclined to say that if a person woke up with all the memories and mental life of the prince, then looked down to see the cobbler s body, they would in fact be the prince. If the prince had committed murder the day before, who would you think should go to jail for it? This suggests a different criteria for personal identity: Memory Criteria Persons A and B are the same person if and only if A remembers being B or B remembers being A.

Memory Criteria Persons A and B are the same person if and only if A remembers being B or B remembers being A. The memory criteria faces several difficulties: (i) It seems like a person doesn t cease to be themselves even if they blackout drunk (ii) There are things I used to remember but no longer remember, but if so, then it implies identity is not transitive, which is absurd. We can try to fix these problems by adjusting the criteria some. In particular, we think that we are connected by remembering our past, but it is still us if we later forget. We could try to summarize this: Revised Memory Criteria Persons A and B are the same person if and only if (1) A remembers being B (or vice versa) or (2) A and B are connected by a series of persons such that each person remembers the previous one.

Teletransporters However we revise the criterion, it seems to face a bizarre objection related to teletransporters Suppose in the future we develop an incredibly fast method of transportation that allows us to travel to Mars in the matter of an hour. The way the system works is that it slowly deconstructs your body while scanning the exact location and state of every atom. It then transports this information by radiowave to a machine on Mars which then rebuilds you pieceby-piece. Would you be willing to use a teletransporter? What about if it didn t destroy you? If the person on Mars isn t you, then it seems like any persistence criteria based on psychology or arrangement of parts is false.

Continuity One might be tempted to think that I can t survive teletransportation because it wouldn t be me, it would be a copy of me, and only the original actually is me. What then does it take to be the original rather than a copy? One option is to return to Mereological Essentialism, but then the original me never survives more than a few seconds Instead, it seems like we should revise it to allow for some replacement of parts over time and instead try to track the unified whole through spactime. Spatiotemporal Continuity Criteria Persons A and B are the same person if they are connected by a continuous path through spacetime.

Continuity Spatiotemporal Continuity Criteria Persons A and B are the same person if they are connected by a continuous path through spacetime. Presumably, a continuous path has to allow that some atoms can diverge off that path while the majority of it stays on that path (if not we have mereological essentialism) However, if some parts can be replaced, how many can be? This leads to the problem of fission

Fission 1 Suppose that in the future you get cancer in the entire right side of your body. Luckily, medical science has advanced to the point where we can figure out the way your body would be without the cancer and 3D print an exact duplicate (made out of carbon and the like). You undergo a prodcedure to remove the cancerous half and replace it with the 3D printed duplicate. Can you survive this operation? Your brain is duplicated on the left and right side, so it seems like you wille be able to retain all your memories, and generally be the same person as you were before, so it seems like you could survive this. However, consider

Fission 2 Suppose that in the future you get cancer throughout your body. There is a radiation procedure they can do but there is an incredibly low chance of suriviving the prodcedure ( 10%); to improve your odds, they decide to split you in half down the middle and do the procedure on each side. If a side survives, then they will complete it as in Fission 1, so you will have a full body and go on to live a happy life. Suppose that, though it was an only 1% chance, both halves survive the procedure and their bodies are finished with the 3D printed bodies. Did you surive the procedure? If so, which one are you? You can t be both for the same reasons you can t be both on Mars and here. Among other things, identity is transitive so if a=b and b=c, then a=c, and clearly the two people after the operation are not identical. You could be one or the other, but what could possibly explain why you are one or the other? Thus, it seems reasonable to say you didn t survive the operation, but why?

Fission One solution to the fission problem would be to say that you need at least 51% of you to survive (i) This has the bizarre result of one single atom making the difference in your survival. (ii) It seems like cancer in 50% of your brain could be solved as in the Fission 1 case just as easily as cancer in 49% of your brain. Why should that last bit of brain material being replaced make the difference? A different option is that we should revise the continuity requirement to say non-branching continuity (i) This has the bizarre result that if the left half survives, it is you if and only if the operation kills the right half. Why should your survival depend on someone else dying? (ii) This would also seem to create moments when it is indeterminate whether or not you survived.

Fission A third solution would be to say that there are two people before the operation and the the operation merely separates them. (i) If the operation brings them into existence, how could it do that? Does it bring one new person into existence, or two? (ii) If only people who will have this operation have two people inside them, then you do not currently know whether there is one person in your head, or two. (iii) If everyone has two people in them, why is it that I never have parts of my conscious experience that are inaccessible to me? (iv) Furthermore, why stop at 2? Couldn t there then be many, many people in this area at the moment? At this point, it is fair to get discouraged with the question and to think maybe it doesn t have an answer.

Deflationism Consider the question, what does it take for the philosophy club to survive? Suppose we are deeply concerned with two issues: Can it survive replacing its members? Can it survive talking about theology rather than philosophy? You might think, this is not a very deep question. All there are are facts about people and what they do. Once we have described who the people are at various times and what the topics are, we have specified everything there is to specify. Whether or not this is the same philosophy club as it was before the president graduated is largely a matter of our interests. If we are interested in sameness of members it is not, if we are interested in sameness of club rules it is, and neither sameness -relation has the right to claim being the correct sameness-relation

Deflationism One could say a similar thing about personal identity. There are the atoms making you up at one moment, there are different atoms in that area at a different moment, and whether or not that is the same person is largely a matter of our interests. For criminal prosecution, we care about memory-continuity. For other situations we care about other types of continuity, and none has the right to claim it is the correct continuity relation. If this is so, then it may be the case that you survive the teletransporter and should be very happy about the fact that that person will have a happy life on Mars. But does this really capture what we want? Surely I want to know whether or not I will be the person alive at a later time, or whether I will be resurrected in an afterlife. It just isn t the same to me if someone a lot like me benefits in these ways.

Do Souls Help? One may be tempted to say that an afterlife is determined by where my soul goes; however, even granting the existence of a soul, we still might want to know what it takes for my soul to be somewhere? It seems like we can legitimately ask what happens to my soul if I step in a teletransporter or if I am split in half? For those inclined to believe in souls and to believe that we get them at conception, keep in mind that fission is not just a hypothetical twins are an example of its actuality. But which twin gets to keep the original soul? However, while it may leave epistemic issues open, it may be useful in providing a basis for personal identity other than the matter involved or the properties of the matter involved (e.g. memory properties)

The Paradox of Personal Identity 1. Whether or not A at time t1 is identical to B at time t2 must depend either on the non-temporal (and non-identity) properties of A and B or on the matter composing A and B 2. Identity across time cannot depend on non-temporal (and non-identity) properties (because of teletransporters) 3. Identity across time cannot depend on material identity (because of fission) 4. Therefore, A at time t1 cannot be identical to B at time t2 (1, 2, 3) 5. For many instances, there is an A at time t1 that is identical to B at time t2.