Phil 86: 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.

• As with Proposal #1, the core idea here is to say what your essential parts are, only now that’s a particular body rather than a particular soul. And this core idea may be elaborated in different ways. Some proponents of Proposal #2 will deny that there are any souls. Other proponents of Proposal #2 will allow that there are souls, and that you have some soul as part of you right now. But they’ll say that particular soul is not an essential part of you. It may be possible for you to continue to exist while that soul is replaced by a numerically different soul (as in the Lockean picture we discussed during the First Night). It may even be possible for you to continue to exist without any soul. Perhaps then you’d be reduced to being an automaton without feelings, or you’d be reduced to being a brute without reason. But if the body which you are still exists, then on this view you’d still be there even if the soul you used to have has left or been destroyed.

• Some versions of Proposal #2 think of the body as something that is essentially a living biological organism. When the body dies, they’d say this organism no longer exists and so you wouldn’t exist anymore either. Other versions of Proposal #2 think of the body as a physical structure that only happens now to be alive, but that would usually still exist for a while even after it dies. On those views, you would still exist even after your body dies. (They don’t say that you’d still be having any thoughts or feelings. You’d just exist as a dead corpse.) Perry doesn’t distinguish these views so we’ll count them all as different versions of Proposal #2. Depending on which more specific version you liked, you may answer questions like these differently:

  • If it’s possible to keep your current body alive, but replace its brain with another brain grown in a lab, or with a cyborg brain that’s made partly or entirely of non-biological material, would you then still exist?
  • In the case of conjoined twins, which seem to be separate organisms that share some body parts like a lower torso, but have a single physical structure (or border between “inside their body” and “outside”), should they count as two persons or as one person?

As noted, Proposal #2 doesn’t have to say that the particular brain you have right now is an essential part of you. A different proposal would insist that the brain, and not the rest of your body, is what’s really essential. Let’s call this:

Perry doesn’t introduce this view into the discussion yet, and we won’t discuss the view further until a few classes later. The objects Perry discusses against Proposal #2 (which we’ll discuss in a moment) would be challenges for Proposal #3 too.

Objections to Proposal #2

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.

  To learn more about why it’s controversial whether imaginability always shows that something is genuinely possible, see these lecture notes.

Souls and Bodies?

We’ve now seen one Proposal — really a group of Proposals — that say your soul is what’s essential to you, and another group of Proposals that say your body is what’s essential to you. (And a third proposal, deferred until later, that say it’s specifically the brain that’s essential, not the rest of the body.) As we’ve mentioned in class, there could also be views that say you are a combination of soul and body, in such a way that both are essentially part of you. We can call this:

(This may or may not have been Descartes’ actual view; this is something scholars argue about.) Perry doesn’t discuss this Proposal specifically, but the objections he discusses against Proposal #1 and against Proposal #2 would all be challenges for Proposal #4 too.

Proposal #5

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