The cognitive neurosciences have acquired a strong degree of legitimacy well beyond that of neurology and psychiatry; their expertise is required in the most diverse domains. This article explores the hypothesis that this social and political success lies in the acquisition of moral authority. This is based on the transfiguration, in scientific languages, of the traditional ideals of regularity of behaviour, beginning in the 18^th century and continuing with behaviourism around 1900, up until the emergence of the cognitive neurosciences at the end of the 20^th century; they were then modified by the ideals of personal change and individual autonomy which became widespread in the last quarter of the 20^th century. The cognitive neurosciences bring to these ideals the promises of an unlimited development of human capacities. This is the horizon of expectation that they create and from which they derive a large part of their authority.