Thanks to Dr. Dale for distilling our debate: “Is there a place in informed assent for this uncertainty about futility?” Drs. Curtis and Burt2 assert that informed assent “should not be offered when clinicians are uncertain about the possibility of success or when the clinicians’ convictions about withholding or withdrawing treatment are based on their value judgments about the patient’s resulting quality of life.” For me, this requisite limits the utility of their construct. Knowledge and experience may increase the likelihood that one’s “certainty” approximates truth. In many cases, I know with near certainty that the withholding/withdrawal of life-prolonging therapies will lead to death. For example, the extubation of a patient with severe ARDS who requires 100% inspired oxygen to breathing room air will almost certainly end with the death of the patient. Some incontrovertible common-sense rules of physiology apply (eg, cells, organs, patients die without sufficient oxygen). However, likely outcomes associated with providing treatments to patients with complex diseases are seldom certain, especially early in the course of treatment. As a trial of therapy proceeds, the patient either does or does not rally. Meanwhile, I learn more about the patient’s predilections regarding invasive medical therapies, and the quality of life and death the patient might find acceptable. Time and the acquisition of more information reduces, but usually does not eliminate, uncertainty (both mine and that of surrogate decision makers). Accordingly, I rarely reach certainty, to practice informed assent rather than informed consent.