24.00 F19 Lecture Handout 15: Parfit on Personal Identity

Handout 15 Parfit on Personal Identity 1. Parfit’s Goals Parfit wants to argue against two claims: (a) Questions of personal identity of the form “Is X the same person as Y” must always have an answer. (b) Unless we can answer personal identity questions in some particular case, we cannot answer several other important questions (survival, responsibility etc.) Parfit is then going to argue that his picture has some important upshots: it makes less sense to have a self-interested theory of morality, and it also makes less sense to be depressed about aging and death. 2. Fission Some cases: Brain Transplant 1: Your brain is transplanted into a new body. The new body has the same character and apparent memories. Brain Transplant 2: Half of your brain is damaged, as well as your body. The healthy half gets transplanted into a new body that has the same character and apparent memories. Fission: Your brain is divided and each half is transplanted into a new body – both resulting people have the same character and apparent memories. (Or: teletransportation) Three options for how to think about fission cases: (1) I survive as one of the two people (2) I do not survive (3) I survive as both people. Argument against (1): No grounds for supposing it to be one rather than the other Argument against (2): P1: In Brain Transplant 1, you survive. P2: In Brain Transplant 2, you survive Why? P1+ people have in fact survived with half their brains destroyed. So it’s plausible that you survive in Brain Transplant 2 as well. P3: The only difference between Brain Transplant 2 and Fission is that in Fission there is more youish stuff around. P4: More you-ish stuff around can’t take you from survival to non-survival. C: In Fission you survive. (P2-P4) Argument against (3): P1: The two fission products, A and B are two distinct people. P2: Identity is a transitive relation. C: A and B are not both identical to C, the original person (P1, P2) Parfit, Derek. “Personal Identity.” Philosophical Review 80, no. 1 (1971): 3–27. © Duke University Press. All rights reserved. 1 Parfit considers the rejection of P1. Why can’t we imagine a single person with 2 bodies? Certain surgical procedures result in “split-brain” – in which there are “two separate spheres of consciousness” each of which controls half of the patient’s body. But it seems much less plausible to think of there being one person with two bodies if the mind is divided permanently and each half develops in its own ways, creates its own memories, etc. What to do? Parfit’s favorite approach: There is no answer. Second to favorite: Answer (3) But the crucial point for Parfit is that the identity question doesn’t matter. Whether you are the same person as one or both fission products or not, what’s important for survival is the relation that exists between you and the fission products, not any questions about identity. Terminological note: Survival does not entail identity “Survival” is being essentially used as code for “what matters when we talk about survival.” (Another option in a similar spirit: Claim that you don’t survive in fission cases, but that’s fine because survival is not what matters.) 3. What Matters for Survival? If identity is not what matters, what does matter? Roughly “psychological continuity.” Parfit thinks that when we take judgments of personal identity to be of great importance, that’s really because in the cases we’re considering, identity implies psychological continuity. Parfit proposes that we think of identity as non-branching psychological continuity. “X and Y are the same person if they are psychologically continuous and there is no person who is contemporary with either and psychologically continuous with the other.” What does psychological continuity consist in? Continuity with respect to things like quasimemory, beliefs, desires, personality traits and so forth. [Parfit defines q-remembering an experience as: “(1) I have a belief about a past experience which seems in itself like a memory belief (2) someone did have such an experience and (3) my belief is dependent up on this experience in the same way (whatever that is ) in which a memory of an experience is dependent upon it.” (15).] 4. Fusion In fusion cases two people come together. While they are unconscious their bodies grow into one. One person wakes up. q-memories can be maintained but some things will be lost. They can’t be both optimists and pessimists, they can’t both intend to go shopping and intend to not go shopping etc… Parfit, Derek. “Personal Identity.” Philosophical Review 80, no. 1 (1971): 3–27. © Duke University Press. All rights reserved. 2 Parfit thinks it’s less absurd to regard fusion as death (=not surviving) than to regard fission as death, since some aspects of your psychology will indeed cease to exist. But he still thinks that enough can be maintained that it seems implausible to regard it as death – especially if a suitable “fusion partner” is selected for you. 5. Refining the Psychological Continuity Account Recall that we defined “memory continuous” as the ancestral of “memory connected.” Similarly, we’ll define “psychologically continuous” as the ancestral of “psychologically connected” (A is psychologically connected to B if and only if A and B share sufficiently similar psychologies, and B’s psychology depends on A’s “in the right sort of way”). Note that connectedness is intransitive, but continuity is transitive. Parfit thinks that connectedness is more important for survival than continuity. Either way though: both connectedness and continuity come in degrees which means that survival, the thing that matters according to Parfit, comes in degrees as well. How much connectedness or continuity is required to count some being as a “past self” of ours might vary in different contexts – it’s up to us what criteria we set, but it will be somewhat arbitrary. 6. The Upshots (a) Self Interest A principle some have found plausible: “Act in your own self-interest” (the interest of your future self) A way to motivate the principle: Act in accordance with what you want + most people want what’s in their own self-interest. Parfit doesn’t object (here) to that. But the self-interest principle is stronger that what’s motivated by this thought. It says you should act in your own self interest whether you want to or not. So now imagine somebody that doesn’t care particularly about the interest of his future self. Once we accept the idea that what counts as a person’s future self is essentially arbitrary – it’s hard to motivate the claim that this person has special reason to care about his own interest more than others. (b) Fear of Aging and Death Whether in-the-distant future “you” actually is you is again, for Parfit, not a deep question. It’s just a matter of how we decide to use personal identity language. So there’s no real reason to fear your own distant death any more than you would somebody else’s. Parfit and Hume’s hope: more of what is bad depends on false belief. Parfit, Derek. “Personal Identity.” Philosophical Review 80, no. 1 (1971): 3–27. © Duke University Press. All rights reserved. 3