Almost everyone will at some point be unable to speak for themselves about medical treatment, and when that happens the law does not go silent — it hands the decision to somebody. This article explains who that somebody is, how they are chosen, and what standard they are supposed to apply. It walks through the two documents that matter most: the one that names a person, and the one that states your wishes. It explains why the naming document is usually the more powerful of the two, why a form signed and filed away often fails at the moment it is needed, and what a POLST does that a living will cannot. It covers what happens when the family disagrees, when the hospital says a treatment is not indicated, and when nobody has any document at all. Real examples show how these disputes actually unfold and how most of them are resolved without a judge. The article closes with the small number of steps that reliably prevent the worst outcomes.