 In the early days of psychiatry, it was widely recognized that there could be lesions of the will, just as there could be lesions of the understanding and affective capacities. Towards the end of the nineteenth century the French philosopher-psychologist Theodule Ribot published a highly influential book on the topic, entitled Les maladies de la volenté—later translated as Diseases of the Will (Ribot 1883). Ribot argued that the capacity for voluntary choice could sometimes be compromised, perverted, or even virtually obliterated, by disease, and that the various impairments that resulted deserved to be scientifically studied and classified. While it is no longer popular to speak of “diseases of the will” contemporary clinicians and researchers do recognize that human will and agency can be impaired or even depleted (Baumeister et al. 1998) in various ways by diseases of many sorts. But there is still little understanding of what such deficits mean for the doctrine of informed consent.