The first rule of conserving a mural is that you will never see it the way its painter did. By the time I am called in, the wall has already lived: soot from a century of candles, a water stain shaped like a continent, the ghost line where a doorway was cut through a saint's robe in 1934. My job is not to return the painting to some pristine origin—no such moment survives to be returned to. It is to decide, square inch by square inch, which of the wall's accumulated lives to honor. Colleagues and I argue about this constantly. When I filled the doorway scar with reversible pigment, one reviewer accused me of falsifying history; when I left the water stain untouched, a donor asked why she had paid for an unfinished job. Both of them believed the mural had a single true state, and that I had simply failed to find it. Standing on the scaffold with a swab of solvent, three inches from brushstrokes laid down before my grandmother was born, I have never been able to believe anything so simple.