Suppose you are replicated on Mars, and the copy of you on Earth is killed ten minutes later. Most people feel like there is some definite answer to whether the Martian is they or someone else. Not an answer got from merely defining ‘me’ to exclude alien clones or not, but some real me-ness which persists or doesn’t, even if they don’t know which. In Reasons and Persons, Derek Parfit argues that there is no such thing. Personal identity consists of physical facts such as how well I remember being a ten year old and how much my personality is similar to that girl’s. There is nothing more to say about whether we are the same person than things like this, plus pragmatic definitional judgements, such as that a label should only apply to one person at a given time. He claims that such continuity of memories and other psychological features is what matters to us, so as long as that continuity exists it shouldn’t matter whether we decide to call someone ‘me’ or ‘my clone’.
I agree with him for the most part. But he is claiming that most people are very wrong about something they are very familiar with. So the big question must be why everyone is so wrong, and why they feel so sure of it. I have had many a discussion where my conversational partner insists that if they were frozen and revived, or a perfect replica were made of them, or whatever, it would not be them.
To be clear, what exactly is this fallacious notion of personal identity that people have?
- - each human has one and only one, which lasts with them their entire life
- - If you cease to have it you are dead, because you are it
- - it doesn’t wax or wane, it can only be present or absent.
- - it is undetectable (except arguably from the inside)
- - two people can’t have the same one, even if they both split from the same previous person somehow.
- - They are unique even if they have the same characteristics – if I were you and you were me, our identities would be the other way around from how they are, and that would be different from the present situation.
So basically, they are like unique labels for each human which label all parts of that human and distinguish it from all other humans. Except they are not labels, they are really there, characterising each creature as a particular person.
I suspect then the use of such a notion is a basic part of conducting social relationships. Suppose you want to have nuanced relationships, with things like reciprocation and threats and loyalty, with a large number of other monkeys. Then you should be interested in things like which monkey today is the one who remembers that you helped them yesterday, or which is the one who you have previously observed get angry easily.
This seems pretty obvious, but that’s because you are so well programmed to do it.There are actually a lot of more obvious surface characteristics you could pay attention to when categorising monkeys for the purpose of guessing how they will behave: where they are, whether they are smiling, eating, asleep. But these are pretty useless next to apparently insignificant details such as that they have large eyes and a hairier than average nose, which are important because they are signs of psychological continuity. So you have to learn to categorize monkeys, unlike other things, by tiny clues to some hidden continuity inside them. There is no need for us to think of ourselves as tracking anything complicated, like a complex arrangement of consistent behaviours that are useful to us, so we just think of what we care about in others as an invisible thing which is throughout a single person at all times and never in any other people.
The clues might differ over time. The clues that told you which monkey was Bruce ten years ago might be quite different from the ones that tell you that now. Yet you will do best to steadfastly believe in a continuing Bruceness inside all those creatures. Which is because even if he changes from an idealistic young monkey to a cynical old monkey, he still remembers that he is your friend, and all the nuances of your relationship, which is what you want keep track of. So you think of his identity as stretching through an entire life, and of not getting stronger or weaker according to his physical details.
One very simple heuristic for keeping track of these invisible things is that there is only ever one instantiation of each identity at a given time. If the monkey in the tree is Mavis, then the monkey on the ground isn’t. Even if they are identical twins, and you can’t tell them apart at all, the one you are friends with will behave differently to you than the one whose nuts you stole, so you’d better be sure to conceptualise them as different monkeys, even if they seem physically identical.
Parfit argues that what really matters – even if we don’t appreciate it because we are wrong about personal identity – is something like psychological or physical continuity. He favours psychological if I recall. However if the main point of this deeply held belief in personal identity is to keep track of relationships and behavioural patterns, that suggests that what really matters to us in that vicinity is more limited than psychological continuity. A lot of psychological continuity is irrelevant for tracking relationships. For instance if you change your tastes in food, or have a terrible memory for places, or change over many years from being reserved to being outgoing, people will not feel that you are losing who you are. However if you change your loyalties, or become unable to recognise your friends, or have fast unpredictable shifts in your behaviour I think people will.
Which is not to say I think you should care about these kinds of continuity when you decide whether an imperfect upload would still be you. I’m just hypothesising that these are the things that will make people feel like ‘what matters’ in personal identity has been maintained, should they stop thinking what matters is invisible temporal string. Of course what you should call yourself, for the purpose of caring disproportionately about it and protecting its life is a matter of choice, and I’m not sure any of these criteria is the best basis for it. Maybe you should just identify with everyone and avoid dying until the human race ends.