When we talk about social identities, we means roles people occupy that significantly affect their life experience. They shape how they relate to other people, and how other people categorize and interact with them. Some of these come from your image or understanding of yourself, what your fundamental values and beliefs and commitments are, what you consider most important to who you are, and how you organize the story of your life. Some of them come from what other people see when they look at us (our skin color, the kind of hair we have, our handicaps). We may not “identify with” or welcome all of these roles. The meaning of a particular role may vary in different parts of the world; or may vary depending on what attitude the person in the role has towards it. But it’s not entirely up to us which roles we occupy, and how they’ll affect our life. It can sometimes be our choice; but other times not; and when it is our choice, it may be only in part.
Often these roles will be very public; but others may be kept more private. Some of them may be kept so private that you’re the only person who knows you occupy the role.
About some of the roles, we may say: this is (part of) who I am, this is what makes me unique.
Nonetheless, most often these roles aren’t essential to us, in the sense we’ll unpack below. In principle, it would be possible for you to exist without occupying the role. Even if that would make you an importantly different person, it could still be you that happened to. Some of the roles may even allow, at least in principle, that you could start out occupying it and then later leave. (Or the reverse.)
In philosophy, when we talk about the essence or nature of something, we mean whatever properties it could not exist without. Those properties such that, if they were not exemplified, it could not be that thing.
Properties that something must have, in this sense, we call essential to it, or necessary properties of the thing. These need not be the properties that are most important or that anyone most values about the thing. For example, an athlete may value her dedication and agility. These properties are important to her. They may be central to how she thinks about herself. But it’d be possible for her to lose her dedication and agility while still being the same person. She could still continue to exist. She might complain, “I used to be more agile; I used to compete in events so-and-so.” She’s still (numerically) the same person who formerly did those things. These may be changes she doesn’t like; they may even fundamentally change her personality and outlook on life. But they aren’t essential properties in the philosopher’s sense.
What properties are essential to the athlete, or to you? What these are is controversial and we’re not yet in a position to propose a list. For now, it’s enough that we understand what it means to say some property is essential to you. It means: were that property to be gone, you would no longer exist. Another person may, or may not, exist in your place. But you could not continue anymore to exist, without having that property. That’s what it means for a property to be essential.
Your “nature” in this sense of your essential properties isn’t the same as talking about a “human nature” that merely disposes you in certain directions, or to have certain characteristics.
Nor is it the same as talking about your “fate” (if you have a fate).
Properties that something happens to have, but that aren’t essential to it, we call contingent or “accidental” properties.
This is a funny technical sense of “accidental,” that diverges from the ordinary folk meaning of the word. Consider an athlete who eats an excellent diet and exercises for hours every day, and ends up getting a great physique. Of course it’s not a coincidence that she’s in good shape. It’s not an “accident” in the ordinary way of talking. But in the philosopher’s way of talking, this would still be an “accidental” property of the athelete, because she could (and did!) still exist at some time without having it.
I’ll try to avoid this philosopher’s use of “accidental” and will say “non-essential” instead.
Some non-essential properties, like a body’s shape, are ones that thing can gain and lose. These are sometimes called “temporary” properties. Other properties are not, but at the same time neither are they essential. Suppose you were born in Chicago, but that could have happened differently. Your parents might instead have been in Toronto or Buenos Aires when you were born. So having been born in Chicago is not an essential property of yours. It is however a property that once you have, you can never lose.
When we use adjectives (aquatic
or longer phrases like quickly swimming across the lake
), some nouns (athlete
or strong swimmer
), and verbs (swims
or swims daily in this lake
), we’re talking about what philosophers call
kinds or categories or properties or attributes or qualities.
Sometimes people also say “concepts,” but when people say “concepts,” they sometimes mean not the properties of swimming and so on themselves, but instead our ideas or ways of thinking about those properties. To avoid confusion, I’ll avoid the word “concept” and will stick to words like “kind” or “property.”
When we use other nouns (Michael Phelps
) or expressions like that swimmer
or your pool,
we’re talking about what philosophers call individual things or objects.
When we ask questions about the essence or nature of something, we could be asking either about a kind of thing (property) or about an individual thing.
Questions about kinds/properties: What does it take to be a swimmer? Or a church? Or a ship or table? Or a tree or person?
With trees, plausibly this will include what the thing is made of. To be a tree, you have to be made of wood. (That’s not all it takes. My shelf is made of wood, and it isn’t a tree. But being made of wood is part of what it takes to be a tree.) In other cases, as with ships or tables, plausibly there is more flexibility in what the thing is made of. Tables can be made of wood, of metal, plastic, glass, ice… To be a table, it seems to be more important why a thing was made, and/or how the thing is now being used.
Questions about individual things: What does it take to be this particular person? Or for there to be one church rather than two? Or for one and the same ship to continue to exist through some process?
Sometimes when we say that objects are “identical” or “the same”, we mean just that the objects have many of the same properties. For example, I might say that you and I bought identical laptops, meaning we have laptops of the same model. They are exactly alike. Still, we have two laptops. Philosophers call that qualitative identity.
Other times philosophers use “identity” in a different, numerical sense, meaning “being one and the same thing.” For it to be the case that my laptop and your laptop are numerically identical, it would have to be (for example) that someone stole a laptop from me and then sold it to you.
Put extra effort into trying to understand and keep track of the difference between sameness in the sense of numerical identity, and sameness in the sense of qualitative identity. Here’s another example, that I used in class. Tamar has two children, Alicia and Abe. For Christmas, she bought them each a new red bike. She made sure to get two bikes of the same design and color, else the kids would get upset. So now: Alicia and Abe have the same bikes, and also the same mother. They “have the same bikes” in the sense of qualitatively identical bikes—there are still two bikes, one for each child. They “have the same mother” in the sense of numerical identity. Unlike the bikes, there is just one mother, that they have to share. One and the same person is mother to both of them.
At the microscopic level, two bikes probably have some tiny differences, even if they came off the same production line. But it will be convenient for some of our discussions to ignore this, or pretend the bikes are exactly similar, down to the last detail. They are perfect 3D copies of each other. In such cases, we’ll say the bikes are perfect duplicates. They share all their properties like size, shape, weight, color, and so on. More on this in a moment.
Whenever philosophers say “one and the same thing,” that’ll be a signal that they’re talking about numerical identity.
Sometimes they instead call this “strict” or “quantitative” identity.
Two pieces of chalk, or two Xerox copies of the same original, won’t be numerically identical. They could only be qualitatively identical. Whenever philosophers say “duplicates,” that’ll be a signal that they’re talking about qualitative identity.
In addition to these two senses of “identity” or “sameness,” we have two paired senses of “being different.” Things are numerically different when they fail to be numerically identical, and qualitatively different when they fail to be qualitatively identical.
We generally count things as qualitatively identical or duplicates even if they don’t share all of their properties. For example, I said that two pieces of chalk fresh out of the box can be qualitatively identical — but the one piece of chalk will be held in my left hand, and the other won’t be. Their location is a property they don’t share. The children’s bikes will differ in their locations, and also in who owns them.
To make sense of this, we need to introduce another distinction, between:
and:
Being 70 inches tall is an intrinsic feature or property of me. Being taller than Joe is not an intrinsic property of me. It doesn’t just depend on how I am in myself. It also depends on how tall Joe is. Similarly, being 10 feet away from Joe is not an intrinsic property of me, either.
When philosophers talk about “qualitative identity,” that isn’t understood to include being identical in all extrinsic or relational respects, too. Objects will usually differ in their relations to other things — like whether they are held in my left hand, or how far away they are from the window, or who owns them. To be qualitatively identical, objects only have to share their intrinsic properties.
On most views, objects can continue to be one and the same thing (numerically identical) over time, while they change some of their properties. For example, they can change their location. Most objects can also to some extent change intrinsic properties, like their inner shape or configuration.
For example, consider my stolen laptop. Perhaps when I owned this laptop, it didn’t have any scratches on it. But when you purchased it, it had a St Pauli logo scratched into it. Plausibly, this could still just be a single laptop, that formerly lacked and later acquired that scratch. The scratching didn’t destroy my laptop and replace it with a new one.
Or consider flies. Even a fly frozen in amber can change its location; flies not frozen can also change their shape as they flap their wings; and arguably flies can also lose some of their body parts, but continue to exist. More controversially but still plausibly, some philosophers will argue that the same object that used to be a living fly can now continue to exist as a dead fly. That black shape over there used to be a living fly, but now (although it still exists) is no longer alive.
Or consider the clock on the wall right now. It is presumably numerically identical to the clock that was in that same location five minutes ago, even though its hands have moved.
I’m only saying it’s possible for a clock to continue to be one and the same thing over time, while some of its properties have changed. Of course, if many of its properties changed — say it morphed into a dragon — then perhaps it would no longer be one and the same thing as the clock which was formerly on the wall. Numerical identity is compatible with some of a thing’s properties changing over time; but many objects will stop existing if too many of their properties suddenly change. Or if any of their essential properties are lost. What counts as too much change? This is a difficult question; and for different kinds of things, different answers may be required.
As we explained above, the clock’s essential properties will be those properties it is impossible for the clock to exist without. These need not be the same as the clock’s important or interesting or valuable properties. Many of the clock’s important properties — such as whether it works correctly — will be such that the clock can lose those properties, while still being (numerically) the same clock.
Since the clock is still around — it used to work correctly but now it doesn’t — working correctly isn’t a property it’s impossible for the clock to lose or exist without. That’s not an essential property of the clock. For properties that are really essential to the clock, it needs to be impossible for the clock to lose those properties. If those properties are lost, then we’ll no longer have one and the same thing.
Which properties would be essential to the clock? Perhaps some of these: being a clock, being solid (instead of a liquid or gas), being composed of more than one molecule, and so on. For some of the clock’s properties, it can be difficult to say whether they are essential or not.
Similarly, you have some essential properties too. What these are will be controversial and we’re yet in a position to list them. But what it means to say some property is essential to you is that, were that property to be lost, you would no longer exist. Someone else may, or may not, exist in your place. But you could not continue anymore to exist, without having that property. That’s what it means for a property to be essential. Again, these need not be the same as your most important or most valuable properties. Instead, they are the properties that it is impossible for you to lose. Your wit and charm may be among your important properties. But it’s possible for a person to become un-witty, and un-charming, while still being numerically the same person. So wit and charm are not your essential properties.
A thing’s identity conditions are the facts about that thing in virtue of which it is one and the same object over time, and a different object from its neighbors. When we come back after fifteen years and look at a grown-up tree, what makes it one and the same tree as the tree we sat under together back in 2010? What makes it a different tree from the trees in the neighboring yards (which may be qualitatively very similar)? To answer questions like that is to say what the tree’s identity conditions are.
Questions about personal identity are questions about what the identity conditions for persons are. Questions about when we have a case of one and the same person, and when we don’t.
You are one and the same person as the five-year-old who broke your mother’s vase. (Of course, you are qualitatively different from that five-year-old; but you are numerically identical to him or her.) What makes you the same person as that five year old? What makes you a different person from the guy sitting next to you? To answer these questions is to say what your identity conditions are. That is the main topic of this course.
Some questions about identity conditions will concern how many persons are occupying a single body at one time. We’ll be looking for an account of what it takes to be one person rather than two (or more) at that time.
Often we’ll instead be talking about candidates for being a person where they are picked out or identified at different times. Then we’ll be asking about what sorts of changes could a person exist through? What sorts of changes would be ones where it’s still you who is left around afterwards, and what changes would bring your existence to an end?
Some changes you can undergo and still be around afterwards don’t involve gaining or losing or replacing any parts. In class I gave the example of sitting down or standing up. (Just as the fly we discussed earlier flapped its wings.)
Ordinarily, we think people can also exist through some changes to what parts they have. (Just as the fly lost some of its body parts.) Plausibly, one kind of change you can exist through is getting a haircut. (Some will object: “But I’m not the same after getting a haircut!” To which the reply is: Yes, you are qualitatively different after getting your hair cut. But you are still one and the same person. There is one person whose hair was long and now is short. The barber didn’t cause anybody to cease to exist.)
Another kind of change you can exist through is having part of your liver removed, or your heart replaced. Every year many people get their hearts replaced with new ones. They don’t view it as a form of suicide. It is a momentous qualitative change to undergo; but they don’t view the heart transplant as a way of causing themselves to cease to exist. They think that if the transplant goes smoothly, then the person they are will still continue to exist, after the operation. If they’re right, then one can still be one and the same person, after having one’s heart replaced.
This term, we’ll be considering some more radical kinds of changes, and asking whether these are changes you could exist through: whether you would still be around after these changes took place.
Suppose we grew a clone of you. How similar to you would the clone end up being?
Let’s say we raise the clone in a locked room, with no English newspapers or radio or internet access or anything like that. It’s attended by nurses who never speak English in its presence. It grows up to be 18 years old. Do you think it would be able to speak English?
No? Why not? It’s a copy of you, and you can speak English.
The answer is that clones are just genetically the same as their originals. They can grow up to have very different properties, because what properties you have isn’t just a function of your genes. Your environment also plays a role.
Do you know any genetic twins? They can have very different tastes and opinions. If they have different careers, and went to different schools, then we can expect them to know different things. On a given Monday afternoon, one twin might be thinking about a math problem, and the other one thinking about dinner.
If we ever manage to grow a clone of you, the relationship between you and your clone would be just like the relation between genetic twins. (Except that in the clone case, the “twin” was born much later.)
As we talk about personal identity, we’ll sometimes be talking about perfect duplicates. These are supposed to be much more like each other than a clone would be like its original. They don’t just have the same genes. They are supposed to be molecule-for-molecule identical. So if the one duplicate is digesting a ham sandwich, then so too is the other. If the one duplicate has a chipped tooth, or a broken arm, or a migraine headache, then so too does the other duplicate. At a given moment, their brains would be perfect 3D Xerox copies of each other.
(Of course, just because they are perfect duplicates at one moment T, doesn’t mean they will remain duplicates. Even if our universe is perfectly deterministic (which isn’t clear), things that start out as duplicates can encounter different stimuli because they’re in different locations. So they can end up gradually diverging. When we talk about having perfect duplicates, we’ll be focusing on times before they start to diverge. We’ll only mean that they are duplicates at some given moment T.)
Them being duplicates at T doesn’t mean they were always duplicates before T, either. But many times we’ll be thinking about cases where two objects or people were duplicates from the start of their existence up until time T.
