Obtaining valid consent is regarded as essential before there can be an ethically or legally appropriate medical intervention. The justification is, simply, that patient autonomy should be respected. The patient's body is hers, and she has a right to do with it what she chooses. In order for that choice to be real, it has to be a choice made by a patient who is competent to make it. That competence has two elements. First, the patient must have the cognitive hardware and software necessary to receive, retain and process the information, weighing the benefits and the burdens of the proposed treatment against each other. Second, the inputs must be the relevant ones: the information to be processed must be (i) accurate and (ii) sufficient.