The focus of this paper is the moral and scientific value of ‘expertise by experience’, that is, knowledge based on personal experience of ill mental health as a form of expertise in mental health research. In contrast to individualistic theories of personal autonomy and the first-person in bioethics, my account of shared decision-making is focussed on how a relational approach to the ‘person’ and ‘patient values’ can throw new light on our understanding of ‘voice’ in mental health research. The mistake, I argue, is to think that a commitment to listening to the patient voice in the process of perspective taking implies a threat to ‘objectivity’ in clinical practice and the very concept of evidence in the philosophy of science more generally. Instead, I use Helen Longino's account of epistemic validity in philosophy of science to argue that narrative experience and ‘patient perspective’ should be understood as an ongoing dynamic partnership working between the different stakeholders’ knowledge perspectives. I also address the connection between expertise by experience and the psychiatric significance of the personal self for the entrenched topics of agency, self-hood, personal identity, and self-knowledge in psychiatric diagnosis. In contrast to identity politics, my model of shared decision-making preserves a critical distance between perspective-taking and value itself in self/other appraisal as the gold standard for good clinical practice.