The fundamental goal of advance care planning is to ensure that future clinical care will be shaped by the patient's preferences even if the patient is unable to participate in making his or her own choices. In recent years, a large conceptual and empirical literature has evolved that attempts to provide as solid a basis as possible for designing effective approaches in this area of clinical care. Unfortunately, some of the conceptual work and much of the empirical research start from a basic model of patient self-determination that is fundamentally flawed. This model can be viewed as a central organizing for research and policy about advance directives: a person expresses a clear preference about future care, and if that preference appears to translate directly into a specific clinical choice, and if that preference is repeated over time and across various scenarios with a high degree of consistency and stability, then we have achieved the gold standard of an advance directive for that potential future clinical choice. This central organizing in turn depends on several corollary myths: 1. have well-formed preferences about future care prior to being asked. 2. Clarity, consistency (across scenarios) and stability (over time) are the hallmark features of authentic preferences. 3. The central clinical tasks are: * To obtain clear biopsy results regarding these preferences. * To assess the consistency and stability of these results, and document this stability over time. * To match care to any consistent and stable biopsy results. A serious problem with these myths is their gross oversimplification of the nature and origins of preferences, and of what actually takes place in the elicitation of expressed preferences. As Carl Elliott has observed, People do not always mean what they say; they do not always say what they want; and they do not always want what they say they want. That much is, if not exactly clear, at least uncontroversial. What is controversial is, recognizing this, how to proceed.[1] A serious flaw of most studies of advance directives (and of patients' preferences more generally) is that these studies uncritically call the answer a person gives to a standardized question - often asked using a forced-choice multiple-guess format - the person's preference. The wording of any question matters tremendously, as any intern or resident discussing do-not-resuscitate choices with patients rapidly learns. For example, in a survey several colleagues and conducted of outpatients at Harvard Community Health Plan, 297 respondents agreed, If were in a coma and a short period of extremely intensive hospital care might return me to near-normal condition, would want it, but 75 of these (25%) separately agreed, I would never want to be on a respirator in an intensive care unit.(2) A striking case study that illustrates the inadequacy of the central organizing myth described above was articulated years ago by Dr. Seuss in his book, Green Eggs and Ham.[3] In this story, Sam-I-Am, whom we might view as the physician, asks the simple question, Do you like green eggs and ham? The Patient responds, simply and directly do not like them, Sam-I-Am. do not like green eggs and ham. Knowing that a patient's preferences might vary considerably depending on the scenario, Dr. Sam-I-Am Am then carefully inquires about whether a wide range of alternative situations might affect the Patient's response: Would you like them in a house? Would you like them with a mouse? ... Would you eat them in a box? Would you eat them with a fox? ... Would you? Could you? In a car? Eat them! Eat them! Here they are.... You may like them. You will see. You may like them in a tree! ... Could you, would you, with a goat? Would you, could you, on a boat? In every scenario, with repeated and increasing certainty, the Patient replies unequivocally, finally summarizing in exasperation, could not, would not on a boat. …