The authority of surrogates—often close family members—to make treatment decisions for previously capacitated patients is said to come from their knowledge of the patient, which they are to draw on as they exercise substituted judgment on the patient’s behalf. However, proxy accuracy studies call this authority into question, hence the Patient Preference Predictor (PPP). We identify two problems with contemporary understandings of the surrogate’s role. The first is with the assumption that knowledge of the patient entails knowledge of what the (...) patient’s choice of treatment would be. The second is with the assumption that a good decision reproduces the content of that choice. If we are right, then the PPP, helpful though it might be in guiding surrogates’ decisions, nevertheless would hold them to the wrong standards and in that way could add to, rather than relieve, the stress they experience as they try to do their job. (shrink)