As part of a larger series addressing the intersection of law and medicine, this essay is the second of two introductory pieces. Beginning with the Hippocratic tradition and lasting for the next 2,400 years, the physician-patient relationship remained relatively unchanged under the beneficence model, a paternalistic framework characterized by the authoritative physician being afforded maximum discretion by the trusting, obedient patient. Over the last 100 years or so, in response to certain changes taking place in both research and clinical practice, the bioethics movement ushered in the autonomy model, and with it, a profoundly different way of approaching decision making in medicine. The shift from the beneficence model to the autonomy model is governed legally by the informed consent doctrine, which emphasizes disclosure to patients of information sufficient to permit them to make intelligent choices regarding treatment alternatives. As this legal doctrine became established, philosophers identified an inherent value in respecting patients as autonomous agents, even where patient choice seems to conflict with the physician's duty to act in the patient's best interests. Whereas the beneficence model presumed that the physician knew what was in the patient's best interests, the autonomy model starts from the premise that the patient knows what treatment decision is in line with his or her true sense of well-being, even where that decision is the refusal of treatment and the result is the patient's death.