The purpose of and advance directive / living wills is to allow you to express your preferences concerning medical treatment in a medical situation when you cannot communicate, including at the end of your life. By expressing such preferences in a writing, you are ensuring that your preferences are made known. Physicians prefer these documents because they provide a writing from you as to your medical care and designate the person he / she should consult concerning unanswered medical questions. Rather than having to obtain a consensus answer from your family as to your treatment, the physician knows your preferences and knows who you want to provide decisions when you cannot do so. Also, providing such information and designating a health care proxy provides whose direction is to be followed in the event your family disagrees as to what medical treatment you would want.