 Assumptions about disability and well-being play an important if somewhat less salient role in this context. They figure most prominently when the individual is no longer capable of deciding for herself whether to receive, continue or refuse life-sustaining treatment. For adults once capable of making such decisions, two standards apply to surrogate decision making: substituted judgment and best interest. The first involves judging what the individual would have wanted or chosen if she could want or choose for her current situation; the second involves judging the person’s interests by a standard other than her own. In cases where the adult never had decisional capacity and there is no basis for making a judgment about what the patient would have chosen, the best interest standard applies. But those who judge the best interests of such an adult are prone to the same errors of projection as nondisabled people judging the well-being of disabled people. A nondisabled surrogate might be devastated at losing capacities the cognitively impaired individual never had, or assume that the inability to understand the source of, or reason for, physical pain must be even more traumatic for that individual than it would be for the surrogate. Such judgments are not clearly wrong, but rather speculative; the primary error is in overconfidence.