The relationship between capacity and credibility: implications for epistemic injustice

In this article, we analyse the concept of mental capacity through considerations of epistemic injustice. We suggest that an assessment of a person’s capacity will always involve consideration of their epistemic credibility. Understanding capacity assessments in this manner allows us to illustrate the epistemic exclusions and injustices that can arise. First, attitudes and stereotypes about mental disability and illness, as well as characteristics such as gender and race, can make a significant difference in terms of who is believed and considered credible. We raise concerns for the potential of these biases to influence capacity assessments inadvertently. Secondly, a person deemed to lack capacity has their epistemic agency significantly curtailed; their contributions to the decision-making process are not those of a full epistemic agent, but those of a derivatized subject, giving rise to epistemic exclusion. We further argue that capacity determinations rely on specific hermeneutical resources, namely those based in medical-scientific or legal knowledge, which may be inapt for interpreting the experiences of disabled people and those with mental illness. Finally, we highlight important insights that this approach provides for considering options for reform in practice and in law.