In The Harm Principle, Personal Identity and Identity-Relative Paternalism,1 Wilkinson offers a thoughtful argument about medical decision-making and Derek Parfit’s reductionist account of personal identity. I agree that Parfit’s account can contribute to the ethical analysis of patients’ choices.

My own work in this area emphasises challenges the reductionist account presents to conventional understanding of advance treatment directives, particularly in cases involving people with dementia.2 I have also urged people making directives to consider the harm their directives could impose on future selves with dementia.3 But as Wilkinson points out, Parfit’s account has implications in other medical contexts as well.

Wilkinson presents examples of people making medical decisions that could impose serious harm on their future selves. These examples consider decisions made before a health crisis. Another kind of case involves people in the midst of illness who face a series of ongoing care choices. As people in this situation adjust to their …