The reach of the Mental Capacity Act 2005 is immense – any of us at any time could find ourselves incapable of taking decisions about our health, our welfare, or our finances. But the balance it seeks to strike between protection and autonomy is precarious. The profound ‘hinterland’ of the Act – its philosophical, ethical and moral challenges – are all too often overlooked by those seeking to apply it in the courts or on the ground in clinical or social work practice. The post-legislative scrutiny report upon the MCA 2005 of the House of Lords Select Committee has shown us just how far we have to go in implementing the profound changes it requires. And we are only just at the start of the journey to understand how the Convention on the Rights of Persons with Disabilities will impact upon our approach to these questions.