Drs Black and Morrissey assert that our cautionary note regarding overreliance on the notion of individual autonomy in the care of the critically ill1 does not contain a rigorous account of the principle of autonomy, rendering our conclusions suspect and our recommendations unhelpful. Although we certainly agree that much more has and can be said regarding what autonomy is and what autonomy means, a full explication of autonomy was not our purpose nor necessary to our argument. Descriptions of the conceptual evolution and competing theories of autonomy in medical ethics can be found elsewhere.2 For our purposes, it is enough to note that autonomy, regardless of formulation, always means more than decisional capacity and requires both moral agency and freedom from undue influences. Patients who are critically ill, however, will virtually always have their autonomy compromised by both internal and external factors. The fact that we do not intend to interfere with our patients’ autonomy does not alter the fact that we invariably do as we strive to exert control over the physiologic perturbations that threaten their existence. If we are successful, we will ultimately restore to the patient the capacity of autonomous choice.