What Makes You You
2. Clarifying the Question of Personal Identity
Let me begin by clarifying what it is that I am asking when I ask what makes you the person that you are. What I am looking for is a theory that will tell us who’s who at different times. Suppose we’re looking at a picture from a five-year-old’s birthday party.
You point at one of the kids in the picture and tell me that it’s you.
My question is: what makes that one you? There’s some resemblance, but on the whole you’re physically very different from that little kid. You’re also psychologically very different from the kid, who (judging from the picture) thinks crayons are the most incredibly interesting thing on the face of the earth. You probably have more in common with the adults in the picture than with that kid. So, what is it about that kid that makes her (or him) you?
More precisely, an answer to the question I’m asking will provide a way to fill in the blank in the following sentence:
A at time t is the same person as B at time t* if and only if ___
In other words, when we’re looking at or thinking about a person at one time, under what conditions should we say that this person and a person who exists at another time are one and the same person? In section 3, we’ll consider a number of possible ways of filling in the blank, which will further clarify what it is I’m after.
But before we get there, let me head off two potential confusions.
First, the word ‘same’ is ambiguous, and if you don’t keep an eye on the ambiguity you are liable to get very confused. To see the ambiguity, let’s think about a couple examples. Suppose that Jade buys a Honda Civic, and then Tanner goes out and buys one too. Is it true that Jade and Tanner drive the same car? There are multiple ways of taking that question. I could be asking whether the car that Jade drives and the car that Tanner drives are the same color and make and model, in which case the answer is yes.
Alternatively, I could be asking whether there’s a single car that Jade and Tanner share and take turns driving, in which case the answer is no. Another example: Suppose you saw some shirt at the GAP, and you liked it so much that you bought two of them.
You wore one yesterday, and the other today. I see you today and say: ‘isn’t that the same shirt you were wearing yesterday?’ In one sense, yes: they’re exactly the same design. In another sense, no:
you have changed your shirt since I last saw you.
To put a label on it, I’ll say that two things, A and B, are qualitatively the same when A and B are very similar to one another. I call this sort of sameness ‘qualitative’ because the idea
is that A and B have a lot of the same qualities (color, shape, design, etc.). A and B are numerically the same when A is B. I call this sort of sameness ‘numerical’ because it’s saying that A is the same as B in the way that numbers are sometimes said to be the same number. ‘22 = 4’ isn’t just saying that the number 22 and the number 4 are incredibly similar; it’s saying that ‘22’ and ‘4’ are two names for one and the same number. The cars Jade and Tanner drive are qualitatively the same, but not numerically the same.
The shirts you bought are qualitatively the same, but not numerically the same.
The same ambiguity arises when talking about whether one person is the same as another. When we’re looking at identical twins and say “you two are exactly the same,” what we mean is that they’re qualitatively the same, not that they’re one and the same person. But when we say that Marilyn Monroe is the same person as Norma Jean Baker, or that Muhammad Ali is the same person as Cassius Clay, we are saying that they are one and the same person; they’re numerically the same.
The question I am asking in this chapter is a question about numerical sameness, not qualitative sameness. So, whenever I say
“A is the same person as B,” that means that A and B are numerically the same. When I do want to talk about qualitative sameness, I’ll describe things as “very similar” or “exactly alike”
or “indistinguishable.”
Here’s how failing to track the distinction between numerical and qualitative sameness is going to get you in trouble. You might think: “Wait a minute! I’m not the same as that kid in the photo.
We’re different in all sorts of ways. In fact, I’m changing every second, so I’m not even the same from one moment to the next. I’m not even the same person as the person who started this sentence!” The problem with this line of reasoning is that it runs together qualitative and numerical sameness. Yes, the way you are now isn’t the way the kid in the picture was, and isn’t even exactly the way you were a moment ago. You are not (qualitatively) exactly the same as you were before. But it’s you that was one way then and is a different way now. There’s numerical sameness despite the lack of perfect qualitative sameness from one time to the next.
The second thing I want to clarify is that I’m looking for an answer that’s more than just a mere rule of thumb for telling who’s who. If that were all that I wanted, then answering the question of personal identity would be easy: A at t is the same person as B at t* when A’s fingerprints and B’s fingerprints are exactly alike.
But since I want something absolutely exceptionless, this Fingerprints Account won’t do. To see why that is, consider the following case:
LEAVE NO TRACE
After robbing the mansion, Bekah realizes that she may have left some fingerprints behind. To help ensure that the police can’t prove that she was the burglar, she soaks her fingers in acid, completely searing off her fingerprints. The police track her down and, just as she hoped, they are unable to prove that she committed the burglary.
It’s the same person, Bekah, both before and after the fingerprints are seared off. But the Fingerprints Account gets it wrong: it says that the fingerprintless person with the seared fingertips is not the same person as the person who burglarized the mansion.
Moreover, because I’m after an account of what makes people at different times the same person, it’s not enough for an account of personal identity just to get the right result in all actually existing cases. Here’s an analogy to help see why that is. Suppose I wanted to know what makes someone a bachelor, and you say: Person A is a bachelor if and only if A is an unmarried man who is under eighty feet tall. That would not be an accurate account of what a bachelor is. And yet it’s true that every actually existing unmarried man under eighty feet tall is a bachelor, and every actually existing bachelor is an unmarried man under eighty feet tall. So, what’s wrong with your account? The problem is that being under eighty feet tall clearly isn’t required for being a bachelor; height has nothing to do with what makes someone a bachelor. The in-principle, hypothetical possibility of a ninety- foot-tall bachelor is enough to show that this is not a satisfactory account of bachelorhood.
Likewise, even if no one has actually ever successfully burned off their fingerprints, the mere possibility of a case like LEAVE NO
TRACE is enough to show that the Fingerprints Account is no good. That’s because what we’re looking for is an account of personal identity which has no exceptions even in principle. The same is true for other accounts which we will consider below:
even merely hypothetical examples can serve as counterexamples to those accounts. (For more on how merely hypothetical cases can still be relevant when assessing philosophical claims, see section 7 of the Introduction to this textbook.)
3. Some Promising and Unpromising Answers