Shared decision making takes many forms, involving different kinds of agents who share the requirement that they must have sufficient decision making capacity for the decision in question. Advance care planning (ACP) is commonly viewed as a form of shared decision making between carers and patients who anticipate loosing decision making capacity. What is unclear in this situation is the identity status of the individuals who have become mentally incapacitated and how to evaluate their rights and interests. This is known as the identity problem of ACP.
This paper suggests that the identity problem can be most convincingly addressed by understanding ACP based on narrative views of identity. These views, however create a tension in our current medico-legal framework for attributing decision making capacity. Current laws and guidelines favor maximum inclusiveness and hence mandate supported decision making for those with reduced or only focally preserved decision making capacity. Yet, an ACP framework based on narrative identity and the relevant capacities to construct such narratives results in more demanding capacity requirements than current medico-legal practice requires. The law thus espouses conflicting views as to who can be an appropriate decision making authority for patient care. I therefore conclude that the law governing medical care needs to be clearer about how to resolve the identity problem of ACP. It needs to either revisit its position on ACP or change its stance on supported decision making for those who have only focally preserved decision making capacity.