Perry’s Second Night (Part 2)

The previous proposals we considered made personal identity consist in the continued presence of some one constant ingredient (a soul, body, or brain). Our next proposals aren’t going to do that. Instead, they will focus on how the different parts of a person (including thoughts and experiences at different times) are connected to each other.

Suppose you’re at a baseball game. It’s a double-header. Near the end of the first game, you step out for some food. When you come back, you see that it’s a different inning than when you left. But you’re not sure whether this is still the first game, or whether the second game has started already. That is, you’re not sure whether the inning you saw when you stepped out is part of the same game as the inning you see now.

This raises a question: what is it about the innings, and their relations to each other, that would make them parts of a single game, rather than parts of two different games?

Think about how we should answer that question. That is, try to come up with a theory that tells us when two innings count as parts of a single baseball game. (Some ideas to get you started: The innings have to involve the same teams. They have to take place on the same field. The score in the later inning cannot be lower than the score in the earlier inning.)

We can think of a train as consisting of a lot of boxcars connected to each other in certain ways. Similarly, we can think of a baseball game as consisting of a lot of innings connected to each other in certain ways. The boxcars are spatial segments of the train; whereas the innings are temporal segments of the baseball game. (Sometimes they’re called time-slices of the baseball game — or what we saw Sider in an earlier reading call temporal parts.) Despite these differences, though, there are certain analogies between the two cases. In both cases, we can tell a story about how the segments have to be connected to each other, in order to make up a single train or game.

Let’s try thinking of persons in this way. Imagine a person divided up into a number of different time-slices, or person stages. Can we tell a story about how those time-slices have to be connected to each other, in order to make up a single person? If we could do that, then we’d be able to answer puzzling questions about personal identity. Instead of asking whether A and B are one and the same person, we could instead ask whether a certain person stage A* and another person stage B* are parts of a single person.

I’ll use an asterisk to signal that we’re talking about person stages rather than about whole persons. “A” and “B” name whole persons (compare: baseball games). “A*” and “B*” name temporal segments of persons (compare: innings). We know that A* and B* are not one and the same thing — just as you knew that the inning you saw when you stepped out was not the same as the inning you saw when you returned. But it’s an open question whether the person that A* is part of (that is, A) is one and the same person as the person that B* is part of (that is, B). Again: We’re not trying to figure out whether A* and B* are identical. We know that they’re not. Rather, we’re trying to figure out whether the persons they’re parts of are identical (that is, whether A=B). In other words, we’re trying to figure out whether there is some one person which A* and B* are both parts of.

Our next proposal about personal identity tells us that the way person stages have to be connected, in order to make up a single person, is by memory. Not memory of facts (remembering that such and such happened or is true), but memory of events as you took part in or experienced them. The later stages in a person’s life have to remember such events experienced by the earlier stages. As a first stab, we can formulate this as follows:

Proposal #4 (first stab): Stage A* and stage B* are parts of the same person iff the later stage remembers events experienced by the earlier stage (see Perry Dialogue, p. 26).

However, for a number of reasons, this formulation is too crude. Let’s try fixing it up.

First, we shouldn’t require that the memories have to actually be played back right at that moment. A person needn’t always be contantly remembering everything that ever happened to them. It should be enough that the later stage is able to remember the events.

For another thing, we want to make sure we’re talking about genuine memories, not mere apparent memories. The mere fact that I seem to remember events in Napoleon’s or Sherlock Holmes’s life does not make me the same person as Napoleon or Sherlock Holmes. We just want to consider the memories I have that are real or genuine. As I mentioned in the lecture, we can allow that something is a genuine memory of some event happening even if it is inaccurate in some respects, even if it leaves some details out, and even if the subject isn’t sure that it is a memory.

Third, we want to make sure that we’re talking about events remembered “from the inside.” I remember my sister getting ready for her high school prom, and that’s an event which my sister experienced. But that doesn’t make me the same person as my sister. I remember that event “from the outside,” whereas she remembers it “from the inside.” It’s only the latter sorts of memories that should count when we’re making judgments about personal identity.

Fourth, it’s too strict to require that later stages in a person’s life are able to remember some event experienced by each earlier stage in that person’s life. People can irretrievably forget things, while still remaining the same person. So A* might be an early part of the same person as B*, even though B* cannot remember any of the events experienced by A*. (This is the point of Reid’s “Brave Officer objection” to Locke, which we’ll read in the coming days.)

What we should require, instead, is that there be a sequence/list/chain of person-stages, where the later stage at each link is able to remember events experienced by the immediately preceding stage. So long as A* and B* are connected by such a chain, it is not necessary that B* remembers any of the events that A* himself experienced.

Proposal #4 (improved version): Stage A* and stage B* are parts of the same person iff they are parts of a chain, all of whose later stages are able to genuinely remember “from the inside” events experienced by the immediately preceding stage in the chain.

We can think about it like this: some of the stages are connected by direct psychological links. In the story we’ve told so far, these links are all about memory. When there’s a chain of connections, then everything in the chain counts as psychologically continuous with each other, even if the psychological connections don’t hold between those stages directly.

At the end of the lecture, I mentioned some other ways that a person’s past tends to influence their future, that we might also want to work into our account of what the psychological connections are, along with memory. These include: