Philosophers have debated whether the advance directives of Alzheimer’s patients should be enforced, even if patients seem content in their demented state. The debate raises deep questions about the nature of human autonomy and personal identity. But it tends to proceed on the assumption that the advance directive’s terms are clear, whereas in practice they are often vague or ambiguous, requiring the patient’s healthcare proxy to make difficult judgment calls. This practical wrinkle raises its own, distinct but related, philosophical question: what criteria may the proxy bring to bear when making such interpretive judgments on which the patient’s life may depend? After defending a general policy of enforcing advance directives on normative (rather than metaphysical) grounds, I argue that when advance directives are vague, a patient’s proxy may permissibly make her own fresh evaluation of the patient’s life as a whole and, in so doing, consider how the patient’s character as a demented person contributes or fails to contribute to that life.