The Mental Capacity Act 2005 governs personal decision-making for adults. It incorporates five overarching principles, including that incapacity may not be inferred merely from a person's unwise decisions and that where a person lacks capacity decisions must be made in her best interests. Through analysis of judicial treatment of unwisdom, best interests, subjectivity and objectivity, considered against parliamentary debates on the Mental Capacity Bill and philosophical critique of ideas of (un)wisdom, we argue that these principles are problematically irreconcilable. The Act's radical under-specificity means, paradoxically, that this comes to be resolved through abstracted values, rather than the centricity of the person herself.
