This is a document that makes clear which measures you do and don't want taken on your behalf – most commonly, for example, insertion of a feeding tube or respirator - to prolong your life. It's called a "living will" because it takes effect when you are still alive, but unable to speak for yourself. It is sometimes called a "directive to physicians." Most living wills are limited to cases of terminal illness. While the legal details vary from state to state, all 50 recognize some form of living will. Many states require living wills to be renewed after a certain period, and you can always revoke them at any time.