There are a number of problems that might be termed “Identity” problems, or issues. Many of these have bothered me all of my life, and I have had trouble even framing some of them in words. But I am going to try here.
Basically, they are all related to “why is something one thing and not another”?
One question is: How does the identity of the whole depend on the identity of the parts?:
I have often heard that our cells that comprise our bodies are replaced every seven years. There is the old classic “Ship Puzzle”, which was apparently posed by the ancient Greek: a ship, lets call it “The Proud Mary”, is replaced one board at a time. As the old boards are taken off, they are placed in a scrap pile. Eventually all of the boards are replaced, so that not one of the original boards is still in the ship. Since this happens gradually, the ship retains its identity as “The Proud Mary” at all times. Then one day, someone goes and puts the original boards all back together and says that one to be the true original ship “The Proud Mary”. The other one, he says, is a copy or duplicate. To some people this seems a frivolous problem, but to me it has always seemed to contain some genuine grounds for puzzlement. This puzzle would seem akin to the issue of how we maintain our personal identity in view of the fact that our individual cells are replaced.
Teleportation of bodies, such as is imagined to be possible in the Star Trek TV show, raises similar, even more daunting, paradoxes. If your molecular configuration is radiated to some other location and reconstructed there, is it really you? What if the original is not destroyed In the process of sending the molecular information? Which is the "real you"?
Consider cloning, which in spite of some the popular misconceptions does not pose an identity problem, any more than does the phenomena of identical twins. A few years back, a sheep was cloned. This caused some controversy. But I do not understand why. I suspect that it threatens people’s underlying concerns about identity, though they do not know that that is the cause of their uneasiness about it. In fact, cloning, in contrast to the teleportation problem, poses no such problems. The cloned organism is a different organism, and as it grows it will have no connection with the cell donating original.
What if my leg were replaced? Would I still be me?--of course, there's no problem with anyone accepting that. What about all of my internal organs being replaced? Again, I don’t think there is any question that it would still be “me”. But what about the brain itself? It appears to be an organ, but it is the one that appears to be responsible for my thoughts, for me being who I am. So if Bob's brain is replaced by Mary’s, isn't the being in Bob’s body now really Mary? That is, the person you would perceive in Bob’s body would in fact be Mary. This would clearly argue that the real me is my brain. Just as the real nature of a computer is defined by its processor and memory. All of the organs and limbs are just “peripherals” that have little to do with the personal identity.
But can we imagine dividing the brain somehow? That is, what if the memories are Bob’s but the processor is Mary’s. Is there some reason why this is inherently a contradictory achievement? Is the person standing in front of you with Bob’s body, Bob’s memories, but Mary’s processor Bob or Mary?
Consider this question: “Can two separate or distinct entities be exactly alike?” In our everyday experience, this is of course not something that would ever occur to us, because compound or complex objects (trees, chunks of concrete, baseballs, rabbits, and so on) always have numerous traits that would allow us to label distinct members of their class. Maybe it is not always evident (as with baseballs where they all look very similar), but surely no one doubts that there are differences that could be discerned upon very close inspection. To carry it even further, we note that even if one insisted that there were no discernible differences, then differences could be added (the basketballs could be numbered, or the owners name etched on the surface somehow, etc.).
I have never heard of any set of parents, or even close friends, who have trouble distinguishing the separate identity of twins (although casual acquaintances may have a great deal of trouble telling them apart). In other words, there are always some small distinguishing characteristics that permit the distinction between them to be made.
But electrons are imagined, in physics, as being fundamentally indistinguishable from each other. The same is true of other sub-atomic particles, and even all molecules or atoms of a given type are identical to each other. But, in our experience, can any entity be exactly the same as all others? What insights into the identity problem can the Pauli exclusion Principle give us? The electrons may be in different states, but in a sense the basic electron is assumed to be in every way identical as every other electron in the universe.
Reflect that physics/chemistry/biology do indeed say that our bodies are comprised of particles, atoms, and molecules. As groups of molecules string together, the possibility of distinguishing the configurations becomes possible.
Is it meaningful to imagine being someone else? Why am I me and not someone else (or how do I know I’m have not been someone else, but have just forgotten?). Maybe the question makes no sense, but why does it seem to arise in our minds? What does it mean when we refer to “being in someone else’s shoes”? We seem to be imagining, at least to some extent, what it would be like to be somebody else? Does this make sense, or can it be in any way imagined to be meaningful? While it seems relatively easy to imagine our selves being positioned somehow in another’s body, that would not really seem to be being them. As Douglas Hofstader asks in his anthology “The Minds Eye”, “What is it like to be a bat”? Does it make any sense to ask this, or related questions, that involve our self being transplanted into some other beings consciousness? Does it depend on whether the transplant involves beings of the same order of complexity and intelligence (i.e., does it make sense among humans, but not between say a bat and a human?). Is it possible that our self will really cycle through all possible people’s lives? Would this be a just eschatology? (sort of an analogy with Feynman’s one electron scattering back and forth in time).
Does this have some bearing on what Christians might believe about the nature of Jesus Christ and the incarnation--that is, is it possible, consistent, or reasonable to imagine that Jesus Christ was God but was somehow limited by having to occupy a physical body?
Ann Rice, in Tales of a Body Thief, simply imagines without dwelling on the difficulties, that such an exchange is possible. In fact, this very ingenious and imaginative author has depicted many variations of the mind-body switch scenario...
Aren’t such moral principles as the “Golden Rule”, and Kant’s “Categorical Imperative” based on the perception that it is possible to imagine being someone else? Maybe even on the possibility that in some sense you are or will be that someone else. You are sympathetic at least in part because you can imagine being them.
Isn’t the Marquis deSade’s arguments that he puts into his philosophical (but perversely randy) villains mouths about how morality is a ruse and that no one really has to care about anyone else base on his perception that we are all utterly removed and detached from each other, that there is no reason to care about another because you will no, can not, could not, ever be that other person.
But where does this stop? That is, how different can the being be before it is clearly impossible to imagine being the other? The old Jewish prayer of thanking God that I am not a woman springs to mind. It seems to assume that “I” could have been either. But does the “I” come into existence after my body, or was it there before? Is this just the issue of whether we have a soul or spirit? (Could this be related to the abortion arguments?)I can imagine being a woman, so it seems to be a reasonable switch. In fact, people even have sex change operations. Does a man really become a woman with such an operation? With the above example involving interchanges or transplants involving Tom’s brain and Mary’s body it seems clear that such a switch is possible or at least plausible.
But what about a being interchanged with another being of a different level of complexity? Of course, this could even be an issue within the human realm: IQs differ (but how widely in an absolute sense?)...But can I imagine being a slug, or a sheep, or any living animal.
What if I maintain that in fact you are always being interchanged with other people? That one moment ago you were John Smith, but now he is you and you are him. He has all of the memories and capabilities of me, and vice-versa. Maybe this just keeps happening, involving large numbers of people (or maybe all people). But his probably makes no sense, as it would be indistinguishable, would it not, from no interchange taking place at all.
And of course the big question: What is it like to not exist? Of course, we have in a sense all known this, as we presumably did not exist before we were born (or if we did, I for one do not remember it). Woody Allen said, “I don’t mind dying, I just don’t want to be there when it happens”. “To be or not to be” isn’t the only question (even if that is an option, and Hamlet went on to question that)--there is also, what is it like to “not be”?
Related to this is the issue of, or the position of, solipsism, and the question of how this differs from materialism/atheism picture (where death involves annihilation and hence non-existence). In other words (and this is hard to explain, so bear with me), if we are annihilated at death, then for me the universe does not exist anymore. If it is inconceivable or meaningless for me to imagine being another conscious organism or being, then might I just as well argue that for all practical purpose, solipsism is true. At least in a practical sense.