Capacity, value neutrality and the ability to consider the future.

Calls for the adoption of a universal capacity approach to replace dedicated mental health law are motivated by the idea that the measures designed to protect patient autonomy in legislation such as the Mental Capacity Act 2005 should apply to everyone, including people with a psychiatric diagnosis. In this article it is argued that a diachronic perspective on questions of mental capacity is necessary if capacity law is to play this broader role, but that employing this perspective in assessments of capacity undermines central patient autonomy preserving features of the legislation, which presents a moral dilemma.