A persistent question in discussions of the ethics of advance directives for euthanasia is whether patients who go through deep psychological changes retain their identity. Rather than seek an account of identity that answers this question, I argue that responsible policy should directly address indeterminacy about identity directly. Three sorts of indeterminacy are distinguished. Two of these—epistemic indeterminacy and metaphysical indeterminacy—should be addressed in laws/policies regarding advance directives for euthanasia.