Lecture 14: What matters in survival, and defining the moment of death

What this lecture covers

This lecture finishes the discussion of "what matters" in survival and opens the course's next topic: what death actually is, on a physicalist view. Kagan uses a thought experiment about living to 969 years old (the 'Methuselah case') to argue that strict personal identity, as defined by the personality theory, is not enough to give us what we want from survival; what matters is having a reasonably similar personality, not literally the same evolving one. He then turns to defining death itself, distinguishing bodily functioning from 'personality functioning,' and shows that the body theory and personality theory disagree about when, exactly, a person dies, and even about whether death coincides with ceasing to exist.

After watching, you should be able to explain the Methuselah case and what it shows about 'what matters,' and explain why the body theory and personality theory give different answers about when someone dies, using the notion of P-functioning.

Key ideas

• The Methuselah case: even if your personality evolves gradually and continuously for hundreds of years, so that the personality theory says a person centuries later is still literally you, that far-future person may share almost nothing with your current beliefs, memories, or values.
• Strict identity isn't what we actually want: Kagan argues that in the Methuselah case, being technically 'the same person' offers no comfort, because what we care about is having a reasonably similar personality, not mere continuity of an ever-drifting one.
• What matters may come apart from survival: it's possible to survive (in the sense some theory of identity requires) without getting what matters, and conceivably to get what matters without surviving, as in a hypothetical nightly soul-swap that preserves personality but not identity.
• P-functioning: Kagan's term for the higher cognitive functions (reasoning, self-awareness, communication, creativity) that make a body function as a person, distinct from ordinary bodily functions like digestion and circulation.
• Existence, being alive, and being a person can diverge: depending on which theory you hold, a corpse might still 'exist' (body theory) while not existing at all (personality theory); a body in a persistent vegetative state might be 'alive' without still being a 'person.'
• The body theory's account of death: death is defined by the end of bodily functioning; personhood is treated as a temporary phase of an entity's existence, not an essential property.
• The personality theory's account of death: death (nonexistence) occurs when the personality stops, which can happen before the body itself stops functioning, requiring a distinction between the death of the person and the death of the body.
• Practical stakes: these distinctions matter for real questions like organ donation from a body in a persistent vegetative state, and, by extension, debates about the moral status of a fetus at the early stages of development.

Walkthrough

A case for the same evolving personality (0:00)

Kagan revisits his claim that strict survival is not enough to give us what we want, using the personality theory as an example: even though it only requires a continuously evolving personality (not identical beliefs at every moment), he constructs the Methuselah case, where gradual change over hundreds of years leaves a person with almost no resemblance to their earlier self. Even though the personality theory says this later person is literally you, Kagan argues this gives you nothing you actually wanted, concluding that what matters is having a sufficiently similar personality, and that this, rather than strict survival, might be all that matters.

What is it to die? A breakdown of functions from a physicalist's view (10:48)

Kagan turns to defining death on the physicalist view. He introduces a distinction between ordinary bodily functions (digestion, circulation) and 'P-functioning,' the higher cognitive functions associated with being a person. In the normal case, these stop at the same moment, but in principle they can come apart, raising the question of which loss actually marks the moment of death.

Identifying the moment of death for the body (19:24)

Considering a corpse (bodily and personality functioning both stopped), Kagan shows the two theories disagree sharply: on the personality theory, you cease to exist entirely once there's nothing with your personality, but on the body theory, you (as a body) continue to exist as a corpse, just no longer alive. He notes this shows that mere existence, on the body theory, isn't what matters either, since being a corpse isn't what anyone wants from survival.

When does personality begin or cease to exist? (30:26)

Using a case where personality functioning stops before bodily functioning does (such as a persistent vegetative state), Kagan shows the body theory must treat being a person as a temporary phase rather than an essential property, since the body can persist without still functioning as a person. The personality theory, by contrast, says the person ceases to exist as soon as personality functioning ends, even while the body remains biologically alive, forcing a distinction between the death of the person and the death of the body. He briefly notes the same puzzle applies in reverse to the earliest stages of life, with relevance to debates about abortion.

What has the right to live: me or my body? (40:09)

Kagan applies these distinctions to a practical case: organ donation from a body in a persistent vegetative state, where personality functioning has permanently ended but bodily functions continue. He asks whether it is the person or merely the body that has a right to life in such cases, noting that both the personality theory and body theory open the door to saying that removing organs would not be wrong, since what's alive at that point may not be a person. He closes by revisiting a simpler puzzle: since people go in and out of P-functioning every night during dreamless sleep, an account of death as 'the end of P-functioning' can't be quite right, setting up the next lecture's refinement.

Before you watch

• Watch the previous lecture, where Kagan concludes both the body theory and personality theory need a no-branching rule and begins distinguishing survival from what matters.
• Keep the definitions of the body theory and personality theory of personal identity in mind, since this lecture continually contrasts what each implies about death.

Check your understanding

1. Explain the Methuselah case and why Kagan thinks strict personal identity, as defined by the personality theory, does not give us what we actually want from survival.
2. What does Kagan mean by 'P-functioning,' and how does it differ from ordinary bodily functioning?
3. Why does a corpse 'exist' according to the body theory but not according to the personality theory?
4. Explain the distinction between the death of the person and the death of the body, and why the personality theorist needs it but the body theorist, in Kagan's account, needs a related but different distinction.
5. Why can't 'death is the end of P-functioning' be exactly right, given what happens to people during dreamless sleep?