Competing interests: KW receives research funding from the Wellcome Trust; KWMF is fellow of St Catherine’s College and member of the Philosophy Faculty, University of Oxford; emeritus professor of Philosophy and Mental Health, University of Warwick; founder director of the Collaborating Centre for Values-based Practice in Health and Social Care, St Catherine’s College, Oxford; and founder editor, Philosophy, Psychiatry, and Psychology. PK is a fellow of St. Catherine’s College, Oxford. AH is the clinical tutor in surgery, University of Oxford: a fellow of St Catherine’s College, Oxford.