We undertake to bring a phenomenological perspective to bear on a challenge of contemporary law and clinical practice. In a wide variety of contexts, legal and medical professionals are called upon to assess the competence or capacity of an individual to exercise her own judgement in making a decision for herself. We focus on decisions regarding consent to or refusal of medical treatment, and contrast a widely recognized clinical instrument, the MacCAT-T, with a more phenomenologically informed approach. While the MacCAT-T focuses attention on individual cognitive performance criteria, an approach oriented by second-person phenomenology brings into view the complex role of time, others and identity in constituting the capacity for individual autonomous judgement. Our phenomenological analysis has consequences both for the practice of capacity assessments and for further research in this arena. Good practice in capacity assessment must attend to decision communities, distributed capacity, and temporal competence, while research on mental capacity will miss the phenomenon if it trains its focus ‘between the ears.’ We illustrate our approach by considering two recent cases of contested capacity: one involving cognitive disability in a dysfunctional decision community, the second presenting the possibility of competent decision-making under conditions of paranoid schizophrenia.