Split your brain into two working bodies — which one is really you?

Parfit imagined a brain divided in half, each half transplanted into a different body, both waking up with his full memories and personality. Neither can be identical to the original, so Parfit concluded personal identity isn't what matters in survival — continuity is.

— Derek Parfit, Reasons and Persons — 1984, Part III
Go deeper: get the book →