8.3 Problems for Locke's View of Personal Identity

What this lecture covers

Building on Locke's claim that personal identity is grounded in continuity of consciousness and memory, this lecture works through a series of objections to that view and shows how far the theory can be repaired.

You will see Thomas Reid's classic counterexample to Locke, the technical fix using an "ancestral relation", and two further problems - quasi-memory and gaps in consciousness such as sleep or coma - that push the discussion toward thinking bodily or brain continuity may matter after all.

Key ideas

• Reid's general/lieutenant/child case: memory alone as a criterion of identity breaks transitivity, since the general remembers being the lieutenant, the lieutenant remembers being the child, but the general does not remember being the child.
• Ancestral relation: a recursive definition (as with "ancestor") lets X count as memory-continuous with Y if X remembers Y's actions, or remembers the actions of someone memory-continuous with Y, fixing the transitivity problem.
• Continuity without constant recall: the ancestral relation also explains why you remain the same person through a day even though you cannot, at any one moment, recall everything from hours earlier.
• Quasi-memory problem: a memory criterion risks circularity, since a "genuine" memory is defined as one of your own experiences; the criterion must instead rely on "apparent" or quasi-memory.
• Sleep and coma: if personal identity depends on continuous consciousness, gaps such as sleep or a coma become a problem, since consciousness appears to switch off.
• Bodily continuity as a fallback: cases like coma suggest that when someone's memories and behavior resume as before, we rely on continuity of the same body or brain to say it is the same person.

Before you watch

• Watch the previous lecture on Locke's account of personal identity, since this lecture assumes you already know his consciousness-and-memory criterion.
• Recall the basic logical requirement that identity is transitive, since Reid's objection turns on that point.

Check your understanding

1. Why does Reid's lieutenant/general/child case create a problem for a simple memory-based criterion of personal identity?
2. How does the "ancestral relation" solve the transitivity problem raised by Reid?
3. Why can Locke's theory not rely on "genuine" memory as its criterion without becoming circular?
4. What does the coma case suggest about the role of the body or brain in personal identity?