Phil 89: Perry’s Second Night (Part 1)

Proposals #2-3

The second proposal about personal identity says that personal identity is just a matter of having the same body:

• What is it to have the same body over time? This is a difficult question. (Compare: what is it to have the same ship over time?) Having the same body over time doesn’t require having exactly the same cells and physical characteristics: one can continue to have the same body even though some of that body’s cells have died and been replaced. For the purposes of this class, we have to set philosophical difficulties about bodily identity aside. We have some grasp of the notion of bodily identity, and that will have to be enough for now. To make things easier, when we discuss personal identity, we’ll always deal with cases where it’s clear which bodies are identical to which other bodies.

A variant of proposal #2 would say instead:

But we won’t discuss this view until a few classes later.

Objections

Sam Miller objects to Proposal #2 with an argument much like the arguments Gretchen used against Proposal #1. He argues that, if Proposal #2 were correct, then it would be much more difficult to have knowledge or reasonable beliefs about personal identity than we ordinarily take it to be. One assumption that we ordinarily make is that one can have reasonable beliefs about one’s own identity over time, without having to check and see if one has the same body as one did formerly. But if Proposal #2 were correct, then it’s hard to see how we’d be entitled to that assumption (see pp. 19-21).

Sam also objects to Proposal #2 on the grounds that it seems possible for a person to wake up in a new body than he or she formerly occupied. Certainly we can imagine this happening. We can even imagine it happening to ourselves! But according to Proposal #2, this would not in fact be possible (pp. 21-22).

• We have to be careful with criticisms like this second one. As you’ll see if you read more about philosophy of mind or philosophy of language, the mere fact that we can imagine some event is nowadays not widely agreed to show that the event is genuinely possible. For example, a materialist will grant to Descartes and other dualists that we can imagine existing without any body, but the materialist denies that this is genuinely possible. Similarly, the proponent of Proposal #2 might accept that we can imagine coming to occupy a new body. He just denies that this is genuinely possible.

  But if you think that it is genuinely possible (even in principle) to come to occupy a new body, then you should reject Proposal #2.

Proposal #4

The next proposal about personal identity will take several classes to introduce and evaluate…